US2891212A - Current balancing transductors for parallel connected diodes - Google Patents
Current balancing transductors for parallel connected diodes Download PDFInfo
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- US2891212A US2891212A US628325A US62832556A US2891212A US 2891212 A US2891212 A US 2891212A US 628325 A US628325 A US 628325A US 62832556 A US62832556 A US 62832556A US 2891212 A US2891212 A US 2891212A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
- H02M7/08—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode arranged for operation in parallel
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/12—Modifications for increasing the maximum permissible switched current
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/14—Modifications for compensating variations of physical values, e.g. of temperature
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/74—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of diodes
Definitions
- My invention relates to a reactor means for forcing a predetermined current distribution between parallel connected diodes of the semi-conductor or metallic type as set forth in copending application Serial No. 628,324 filed December 14, 1956 entitled Current Balancing Reactors for Rectifier Elements to Isadore K. Dortort and assigned to the assignee of the instant invention, wherein the reactor has two cores of square loop hysteresis material which are biased in opposite directions.
- the principal object of my invention is to provide a reactor means for forcing an equal or a substantially equal current distribution between a plurality of parallel connected diodes, even though their forward conducting characteristics are not matched to one another.
- a reactor system comprising a through-type balancing reactor in a so-called whiie tree arrangement.
- a main current carrying bus is divided into two branches. Each of these branches is then connected to form a first and second winding of a magnetic core, whereby the flux induced in the magnetic core due to the rst and second winding are in opposing direction.
- the voltage of the first branch will be reduced, and the voltage in the second branch increased by an equal amount, and in just sutiicient amount to increase and decrease their currents respectively, so that they will diifer by no more than the required magnetizing current.
- the iiux of the reactor during any conductive cycle is varied in only a single direction, this flux being decreased to its residual ux density during the blocking cycle of the respective series connected diode.
- the reactor cores should be of the type having a low residual magnetization wherein small air gaps could be utilized to achieve this end in the absence of special reactor control systems as will be set forth hereinafter.
- the first and second branch thus being balanced to carry a substantially equal current within the limits of the magnetizing current of the reactor may then each form a further first and second branch, each of which is taken through a reactor in a manner similar to that described above.
- the outputs of these two reactors will then have four current branches wherein the current in each of the branches is substantially equal within the limits of the magnetizing current of their controlling reactors.
- each of the four output branches could be further subdivided with the use of further balancing reactors whereby eight output branches would be provided at which points diodes would be connected to carry an equally distributed load current.
- a second embodiment of the above invention could comprise a simple series reactor connected in series with each of the individual diodes wherein each of the impedances are substantially equal and iixed and are of such a value that the reactor impedance drop is substantially larger than the variations of forward resistance drop between diodes.
- the variation in forward resistance from diode to diode which results in the current unbalance will be a smaller percentage of the total branch impedance whereby the current unbalance from branch to branch will be reduced similarly and current balancing will result.
- t'ne reactors could be comprised of a substantially U-shaped iron core which is simply slipped over a conductor in series with an associated diode, the air gap between the adjacent ends of the reactor core providing a reactor which will not saturate at peak forward current, and having the desired low residual magnetiza tion to prevent the subsequent saturation of the reactor which would occur since this reactor is subject to repetitive uni-directional pulses.
- this U-shaped lamination could be a substantially circular lamination having an air gap cut therein wherein laminations are stacked around the conductor to be connected in series with the diode until the required reactor size is achieved.
- each reactor core may be provided with a small secondary winding wherein the secondary windings of each reactor are connected in series to thereby reduce the effective impedance and still force proper current division within the limits of the magnetizing currents of the reactors in a manner similar to that described by the throughstype reactor.
- a still further embodiment of the above invention in application Serial No. 628,324, filed December 14, 1956, would be in the utilization of the couplet type reactor used in a chain or cascaded arrangement. More specifically, in the couplet type of system, the conductors of a" first and second diode will be coupled by a magnetic core so that iluxes are induced in the core in opposite directions. The conductor of a third diode is then coupled to the conductor of the second diode by a second magnetic core so that once again lluxes are induced in the second magnetic core in opposite directions by the currents in the second and third diode conductors.
- any desired number of conductors which include diodes which are to be connected in parallel may be added to the above noted chain by providing a magnetic core for coupling to adjacent diode conductors so that the fluxes in the core will be induced in opposite directions. So long as the chain arrangement is utilized and the iirst diode conductor is not coupled to the last diode conductor added to the system, the maximum current imbalance between the individual diodes cannot exceed the total magnetizing currents of all the core used minus one.
- l can utilize cores of the highly grain oriented type by providing a first and second core for each reactor wherein the cores are biased to saturation by a D.C. bias in opposite directions.
- one of the cores will change in flux from a first saturation value to some value below its saturation in the oppo* site direction, while the other core remains saturated.
- the cores will be returned to their initial opposite saturations during the inverse voltage portion of the cycle so that they may operate on the successive cycle.
- the primary object of this invention is to provide improved reactor means for forcing an equal. current distribution between a plurality of parallel connected 4 diodes wherein the reactor is of the type having a relatively small magnetizing current.
- a further object of this invention is to ⁇ utilize reactors having double cores of square loop hysteresis material wherein each core is biased to an opposite saturation, the iirst core operating to decrease diode current in a first of a pair of diode conductors, the second core operating to decrease diode current in a second of said pair of diode conductors.
- Figure 1 shows a single phase halfwave rectifier having a plurality of diodes connected in parallel.
- Figure 2 shows the forward voltage characteristics of the diodes of Figure 1.
- Figure 3 shows the application of balancing reactors to the circuit of Figure l for forcing a substantially equal current distribution between the diodes.
- Figure 4 shows the forward voltage drop on two of' the diodes of Figure 1.
- Figure 5 shows another embodiment of balancing type reactors.
- Figure 6 shows a still further embodiment of balancing type reactors.
- Figure 7 illustrates my novel invention wherein straight-through reactors are applied to the circuit of Figure 1.
- Figure 8 is an exploded perspective view showing the mechanical construction of the through-type reactors of Figure 7.
- Figure 9 shows the manner in which secondary windings may be applied to the reactors of Figures 7 and 8 for forcing a more nearly equal current balance between their associated diodes while reducing the effect of the reactors on power factor.
- Figure 10 shows an application of my novel invention wherein couplet reactors are applied in an open chain relationship.
- Figure l1 shows a further application of the couplet type reactors to a closed chain system.
- Figure 12 shows how an open chain of couplet reactors for an odd number of diodes may be connected in a closed chain relationship.
- Figure 13 shows how an even number of diodes con nected in an open chain by couplet reactors may be connected in a closed chain relationship.
- Figure 14 illustrates one possible physical arrangement of an open chain couplet reactor system.
- Figure l5 shows the bus and bus lianges of the de'- vice of Figure 14.
- Figure 16 shows a view of Figure 15 when taken across lines 16-16.
- Figure 17 shows a view of Figure 14 when taken across the lines 1717.
- Figure 18 shows a View of Figure 14 when taken across the lines 18-18.
- Figure 18A shows how the coupling reactors may be modified to allow conductor entrance to the bus of Figure 14 from the same side of the bus rather than from alternate sides.
- Figure 18B shows a side View of Figure 18A.
- Figure 19 illustrates how the reactors of my novel. invention may be adapted to allow the use of high residual tlux density material having relatively low magnetizing current.
- Figure 20 shows the magnetic characteristics of the ever, that the use of a single phase rectifying systemv isv to be taken for illustrative purposes only, since my novel invention is clearly ⁇ applicable to any type of rectifier ⁇ connection so long as diodes in any branch are to be connected in parallel.
- Figure l shows a single phase A.C. voltage source 30 connected to energize a D.C. load 32 through the parallel connected diodes 34, 36, 38 and 40.
- the forward voltage characteristic of each of diodes 34 through 40 is shown in Figure 2 where it is seen that since each of the diodes of Figure l has a forward voltage drop V1, the current through each parallel branch is diierent. That is to say, diodes 34, 36, 38 and 40 conduct currents having the magnitudes I1, I2, I3 and I4 respectively.
- the principle of my invention is to provide a reactor control means which is so constructed that the currents in each of the parallel branches will be forced to maintain a substantially equal distribution.
- Figure 4 which, for illustrative purposes, shows the wave shapes of the forward voltage drops of the branches containing diodes 34 and 36 of Figure 1 as voltage drops V1 and V2 respectively, these voltage drops are to be controlled by the reactor means of my invention so that an equal current distribution will result. That is to say, the reactor means operating on the current I2 will cause a difference in forward voltage drop for the two diode branches in accordance with the voltage time area which is given by the shaded area of Figure 4, this area being equal to the integral of V1 minus V2 where V2 is the voltage drop on diode 36 times the differential in time. Thus the diode currents may now be adjusted to the same value.
- FIG. 3 One type of reactor means which satisfies the above condition in accordance with my novel invention is setv forth in Figure 3 wherein the circuitry of Figure 1 has been modified to include the through-type reactors 42, 44 and 46 which are connected in a Whiffle tree type arrangement for forcing the desired current equalization. More specifically, the right hand end of source 30 is broken into a first and second branch which include Windings 48 and 50 respectively on the core 42. These two windings are so connected that they will induce M.M.F.s in the core 42 in opposing directions.
- Each of the two branches including windings 48 and 50 are then further branched, the branch including winding 48 being subdivided into branches including windings 52 and 54 while the branch including winding 50 is subdivided into the branches including windings 56 and 58.
- FIG. 5 shows a double Y secondary wherein the yneutral points of the Y connected secondary windings 60 and 62 are connected through an interphase transformer 64, the center of which is connected to one side of 1a load 66.
- Each phase of secondary windings 60 and 62 is then taken out in the manner substantially identical to that shown in Figure 5 for the case of phase A which is the only phase shown, in order to simplify the diagram.
- a multi-legged core (one leg for each rectifier element) is then provided for each of the phases wherein the D.C. component fluxes are cancelled out by having diametrically opposite ph-ases connected through opposing windings.
- phase A of winding 60 is connected to the coils 68, 70 and 72 which are in turn connected in series with rectiers 74, 76 and 78 respectively which then connect to the opposite side of load 66.
- phase A is connected to windings 80, 82 and 84 having their associated diodes 86, 88 and respectively similarly connected to load 66.
- windings 68, 70 and 72 of the balancing reactor will maintain an equal current distribution between diodes 74, 76 and 78 in the same manner as has been set forth in the case of Figure 3.
- windings 80, 82 and 84 will maintain equal current distribution between their associated diodes 86, 88 and 90 respectively. Because of almost complete cancellation of D.C. ampere-turns, almost the com.- plete flux change can be utilized.
- a similar arrangement may be provided for the three phase bridge connected rectifier system of Figure 6 where three parallel diodes are connected in each leg of the bridge. If more than three rectifier elements are connected in parallel, the balancing reactor has more than three legs-one for each element. The tertiary winding is then connected as a regular polygon.
- a delta connected secondary winding 9S for energizing a D.C. load has a three-legged core which includes windings 100, 102 and 104 for maintaining equal current distribution through diodes 106, 108 and 110 respectively. Similarly, windings 112, 114 and 116 maintain equal current distribution between diodes 118, 'and 122.
- Windings 112, 114 and 118 are moved in opposite polarity to windings 100, 102 and 104 to cancel the D.C. ampere turns. Once again, overall impedance is reduced, power factor improved, and voltage distribution is improved by the delta connected tertiary which includes windings 124, 126 and 128.
- Figure 7 shows how the circuit of Figure l could be adapted by reactance means of the series connected type.
- reactors 130, 132, 134 and 136 are connected in series with diodes 34, 36, 38 and 40.
- reactances 130 through 136 so that they will have a substantially higher impedance drop than the resistive drop of their corresponding diodes 34 to 40 and further making the reactance of reactors 130 through 136.
- a; substantially identical value, thenA the current unbalancewhich isnow controlled by a much higher irripedance will be substantially independent of the diode resistance inthe tforward direction thereby allowing a relatively. greatly. improved current balance between the diode, branches.
- This system is highly desirable since it lends itself to extremely simple manufacturing techniques.
- Figure 8 shows that each of the reactors could be comprised of stacks of laminations 138, 140, 142 and 144 which have openings therein 'for allowing the passage of associated diode conductors as well as air gaps such as air gaps 146, 148, 150 and 152 respectively.
- the device of Figure 8 shows the A.-C. source 30 as being connected in series with a. main bus 154 to which conductors 156, 158, 160 and 162 are attached.
- Each of conductors 156 through 162 is further provided with threaded ends which as will be seen hereinafter cooperate with fastening nuts 164 through 170 respectively.
- Each of conductors 156 through 162 therefore comprise a single turn winding for the reactor' cores 138 through 144 respectively.
- the individual diode assemblies 131i, 132, 134 and 136 are commonly provided with flexible conductors terminated by electrical connecting means 180, 182, 184 and 186 respectively, while their other ends are connected to a second common bus 188 in any desired manner. Accordingly, by inserting conductors 156 through 162 through their respective ⁇ reactor cores and corresponding diode terminals 180 through 186 respectively and thereafter tightening nuts 164 through 170 so as to achieve mechanical positioning of the reactors as well as electrical engagement of diode terminals 180 through 186 and conductors 156 through 162, the A.C. source 30 may deliver rectified power to the llt-C. load 32 as indicated in Figure 7.
- the material utilized in coresl 138 through 144 could be in laminated tform or solid form, depending upon yallowable eddy current and hysteresis conditions.
- air 146 through 152 respectively be provided (in the absence of auxiliary means which are to be ascribed hereinafter) since it is necessary to avoid sat tion at peak forward currents and to have a small i. .ual 'ilux density within the core ⁇ in view of the unidirectional cnergization thereof. That is to say, while the cere is operative, its fiux change occurs only from the point of residual magnetization to a point near saturation magnetization. Hence if as low as possible a residual magnetization is used, the core will be capable of a large flux excursion and would therefore be smaller than one having a small ilux xcursion because of a high residual magnetization.
- Figure 10 illustrates still another embodiment ofn'iy novell invention whereincouplet reactors are utilized, forcoupling the individual diode conductorsA of parallel confnected branches.
- Figure 10 ⁇ spel-ref.. matically illustratesa system of Vparallel connecteddiodes,l wherein conductors 198,200, 202, 204, 2,06, 208,210 ⁇ and 212 each have a single diode connected ⁇ in series, therewith,
- V the circuit corresponding to the ⁇ s chematic illustration of Figure 10. would be similar'. tol'igure, 1 wherein eight rather than four diodes are connected in, parallel and areV to have equalcurrent distributionim.- posed upon parallel connected diodes.
- Coupled reactors 214, 2,16, 2,18, 220, 222, 224 and 226 couple adjacent'branches oftheI parallel system in such a manner that the currenttlowin, adjacent branches is in opposite directions; as indicated by the dots and crosses ot conductors 198 througlr212y which show current ow into and out of; the drawing respectively.
- reactor 214 couples branches 198 and 200 in such, a manner that the fluxes induced in the core 214 due to conductors 198 and 200 are in opposing directions.
- reactor 216 couples branches; 200. and?V 202
- reactor 218 couples branches 202 and 204, and soon down the line until the chain is completed by they cou. pling of conductors 210 and 212 by the core- 226.
- cores 214 through 226 should be of mate. rial having a low residual magnetism in order to ⁇ preventisaturation of the cores by an accumulation of uni-direc,-v tional volt-seconds in successive conducting periods.
- Figure l2 shows the manner in which a parallel group of. con. ductors corresponding to an odd number of diodes may be closed without having to physically circle the configuration. It is to be noted that the configuration of ⁇ Figure l2 is substantially identical to that of Figure 10 with the exception of the omission of core 226 and conductor 212.
- the auxiliary core 230 having an air gap 232 is coupledy to conductor ⁇ 198 while core 234 having an air gap- 2,36 is coupled to conductorv 210which is the lastgconductolj; oi the.v chain.
- Each of; cores-'2.30 and 2345 arefthg provided with auxiliary windings 238 and 240 respectively which can be connected to one another in any desired polarity so as to effect closing of the loop by a simple electrical connection which allows any desired choice of configuration of the chain, yet still providing the desired current balance which is limited to only one-half the magnetizing current of all the cores.
- Figure 13 which is identical to that of Figure may close the loop by means of the same type auxiliary reactors 230 and 234 having auxiliary windings 238 and 240 which are connected as is required to achieve proper polarities of the fluxes in cores 230 and 234 with respect to the flux induced by conductors 198 and 212 respectively.
- Figures 14 through 18 show one method by which the open chain construction of Figure 10 could be accomplished in' a rectifier circuit.
- Figure 14 shows the A.C. voltage source 30, which is to deliver D.C. power to the load 32 as being connected to a bus bar 242 which, as is best seen in Figures 15 and 16, has conducting flanges 244 and 246 fastened thereto in any desired manner.
- the bus may be hollow as shown in Figure 16 to allow passage of a cooling medium.
- Each of flanges 244 and 246 is provided with alternate through holes and tapped openings so as to allow electrical connection by extensions of conductors 196, 198, 200, 202 and 204 to pass through their corresponding coupling reactors 214, 216, 218 and 220 (see Figure 10) in alternate directions.
- the flange plate 244 seen in Figure 15, has a through hole 248, a tapped opening 250, a through hole 252, and then a further tapped opening 254 while ange plate 246 is provided with alternate tapped openings which register with the through hole of flange plate 244 and through holes which register with the tapped openings 250 and 254 of flange plate 244.
- conductor 198 has a flexible portion fastened to a conducting bolt member 256 which passes through a through hole in flange plate 246 through the balance reactor cores 214 and 216 and thereafter threadably engages flange plate 244 in a current carrying engagement.
- the conductor 200 which was to initiate a flux in core 216 which is in a direction opposite to the flux initiated by conductor 198 passes through hole 248 of flange plate 244 and then through the cores 216 and 218 and terminates in a threaded engagement with flange plate 246.
- this alternate type of construction is continued for each of the current conductors of the particular rectitier phase in question.
- the current directions of the conductors of a common coupling reactor are opposite to one another in order to allow the desired current equalization or equal current distribution of current flowing through each of the parallel connected diodes.
- Figures 14 through 18 may be easily modified so as to allow the conductor entrance through the reactor from the same direction or from the same side of the bus while opposite fluxes may still be induced in the coupling reactors by constructing these reactors to have the figure 8 shape set forth in Figures 18A and 18B.
- Figure 18A shows a coupling core 260 which could be used as any of the coupling cores 214 through 220 of Figure 14 as being constructed of a roll of magnet Wire twisted in a figure 8 shaped and formed to nest in any desired manner as shown in Figure 18B.
- FIG. 19 A preferred embodiment of my novel invention using a double core is set forth in Figure 19 wherein a threephase Wye connected transformer winding 270 is to energize a D.C. load 271.
- phase A of the rectier system is shown in Figure 19 and comprises the diodes 272, 274, 276 and 278 and the couplet reactors shown generally by numerals 280, 282 and 284.
- reactor 280 couples diodes 272 and 274
- reactor 282 couples diodes 274 and 276
- ⁇ and reactor 284 couples diodes 276 and 278 in a manner similar to that described for the open chain couplet system described hereinabove, this system being chosen for illustrative purposes only.
- reactors 280, 282 and 284 are further seen to be comprised of two magnetic cores (which are of square hysteresis loop type material) through Which extends the diode conductors and each having an auxiliary biasing winding.
- reactor 280 has a first and second core 286 and 288 which have biasing windings 292 and 290 respectively.
- reactor 282 is comprised of cores 294 and 296 having biasing windings 300 and 298 respectively while reactor 284 has cores 302 and 304 which have biasing windings 386 and 308 respectively.
- Each of the biasing windings 290, 292, 298, 300, 306 and 308 are then connected to a source of biasing potential 310 which caused the two cores of each reactor 280, 282 and 284 to be biased in opposite directions of saturation.
- reactor 280 in view of Figure 20 which shows the characteristics of any of the reactors 288, 282 or 284.
- reactor core 286 is biased to the right of the point of Zero current difference between currents through diodes 272 and 274 by D.C. bias energization Nlm of Winding 292 due to bias means 310.
- core 288 is oppositely biased by N131() to the left of zero current difference by means of energization of winding 290.
- reactor 282 operates in the same manner to equalize currents through diodes 274 and 276 while reactor 284 operates on diodes 276 and 278.
- a current balancing system for a plurality of parallel connected diodes comprising a reactor means connected in series with each of said parallel connected diodes; said reactor means being constructed to adjust the forward voltage drop on its corresponding diode until the forward currents of each of said diodes are substantially similar regardless of their forward voltage characteristics; each of said reactor means comprising a first and second core of high permeability material, each of said first and second cores being biased in opposite directions.
- a current balancing system for a first and second parallel connected diode comprising a first and second reactor winding connected in series with said first and second parallel connected diodes; said reactor windings being constructed to adjust the forward voltage drop on their said corresponding diodes until the forward current through each of said diodes is substantially similar regardless of their forward voltage characteristics; said first and second windings being wound on a first and second common core of square hysteresis loop material in directions to induce opposing fluxes in said cores, ⁇ and biasing means for said first and second core, said biasing means being constructed to produce biasing flux in said first core in a first direction and to produce biasing flux in said second core in a second direction.
- a rectifier system for energizing a D.-C. load from an A.C. source, said rectifying system including a plurality of parallel connected diodes for achieving a predetermined current rating, a current balancing system for forcing a substantially equal current distribution between each of said plurality of diodes; said current balancing system comprising inductive means connected in series with each diode of said plurality of diodes; said inductive means being constructed to adjust the forward voltage across each of said diodes to force equal current through each of said diodes regardless of the forward voltage characteristics of said diodes, said induci tive means being operative throughout the forward voltage conduction cycle of said plurality of diodes; said inductive means including a rst and second core and biasing means therefor, for biasing said first core in a first direction and for biasing said second core in a second direction.
- each phase of said rectifying system including a plurality of parallel connected diodes for achieving a predetermined current rating, a current balancing system for forcing a substantially equal current distribution between each of said plurality of diodes; said current balancing system comprising inductive means connected in series with each diode of said plurality of diodes; said inductive means being constructed to adjust the forward voltage across each of said diodes to force equal current through each of said diodes regardless of the forward voltage characteristics of said diodes, said inductive means being operative throughout the forward voltage conduction cycle of said plurality of diodes; said inductive means including a first and second core and biasing means therefor for biasing said first core in a first direction and for biasing said second core in a second direction.
- a current balancing system for a plurality of parallel connected diodes comprising a reactor means connected in series with each of said parallel connected diodes; said reactor means being constructed to adjust the forward voltage drop on its corresponding diode until the forward currents of each of said diodes are substantially similar regardless of their forward voltage characteristics; said reactor means comprising a couplet reactor for magnetically coupling conductors connected to each of said plurality of diodes into pairs; the conductors of each of said pairs being directed to induce opposing fluxes in their respective couplet reactors, each of said couplet reactors having a first and second core biased in a first and second direction.
- couplet reactors form an open chain having a first and second auxiliary couplet reactor connected to the hrst and last diode conductor respectively of said chain; each of said auxiliary reactors having auxiliary windings thereon connected in series to close the chain.
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Description
June 16, 1959 F. R. BINGHAM QURRENT BALANCING TRANsDucToRs FOR PARALLEL CONNECTED DIoDEs Filed Dec 4 Sheets-Sheet 1 @zahl June 16, 1959 F. R. BINGHAM 2,891,212
CURRENT BLANCING TRANSDUCTGRS FOR PARALLEL CONNECTED DIODES Filed Dec. V14;, 1956 4 Sheets-Sheet 2 Y J2 34 *da f-a -40 Filed DeO. 14, 1956 June 16, 1959 F R' B|NGHAM 2,891,212
`CURRENT BALANCING TRANSDUCTORS FOR PARALLEL CONNECTED DIODES 4 Sheets-Sheet 5 June 16, 1959 ,Filed Dec. 14, 1956 F. R. BINGHAM 2,891,212 CURRENT BALANCING TR-ANsDUcToRs FOR PARALLEL CONNECTED nIoDEs 4 Sheets-Sheet 4 BY ma/fihi United States Patent O CURRENT BALANCING TRANSDUCTORS FOR PARALLEL CONNECTED DIODES Francis R. Bingham, Norristown, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application December 14, 1956, Serial No. 628,325
9 Claims. (Cl. 321-27) My invention relates to a reactor means for forcing a predetermined current distribution between parallel connected diodes of the semi-conductor or metallic type as set forth in copending application Serial No. 628,324 filed December 14, 1956 entitled Current Balancing Reactors for Rectifier Elements to Isadore K. Dortort and assigned to the assignee of the instant invention, wherein the reactor has two cores of square loop hysteresis material which are biased in opposite directions.
Present advances in the construction of the various types of diodes such as the metallic and semi-conductor type with the use of the germanium and silicon elements has led to the increasing use of these members for high current capacity rectifying systems. Thus it is possible, in a multiphase rectil'ier system, to connect a number of diode elements in parallel for each phase, whereby D.C. current capacities of the order of 5000 amperes may be obtained. Since, however, individual diodes vary in their forward voltage charactceristics, the current distribution between parallel connected diodes will not be equal unless the diodes are very closely matched in these characteristics. Furthermore, diode characteristics are changeable with age, temperature conditions, and many other uncontrollable parameters. Thus, even though the diodes may originally have been closely matched to conduct substantially the same forward current, this matching may be unbalanced after a relatively short period of operation.
The principal object of my invention is to provide a reactor means for forcing an equal or a substantially equal current distribution between a plurality of parallel connected diodes, even though their forward conducting characteristics are not matched to one another.
Above noted copending application Serial No. 628,324, tiled December 14, 1956 sets forth a reactor construction which is such that the forward voltage drop of any individual rectifier is automatically adjusted by inductive means depending upon the individual rectifier characteristics so that the total current through each of the diodes is substantially constant.
In one form of the above invention, a reactor system is provided comprising a through-type balancing reactor in a so-called whiie tree arrangement. Thus, a main current carrying bus is divided into two branches. Each of these branches is then connected to form a first and second winding of a magnetic core, whereby the flux induced in the magnetic core due to the rst and second winding are in opposing direction. Thus, if the current through the first branch exceeds the current in the second branch by the magnetizing current of the reactor, the voltage of the first branch will be reduced, and the voltage in the second branch increased by an equal amount, and in just sutiicient amount to increase and decrease their currents respectively, so that they will diifer by no more than the required magnetizing current.
In a similar manner, if the current in the second branch exceeds the current in the rst branch by the magnetizing 2,891,212 Patented June 16, 1959 ICC current of the reactor, the voltage of the first branch will be increased and the voltage of the second branch decreased.
It is to be noted that the iiux of the reactor during any conductive cycle is varied in only a single direction, this flux being decreased to its residual ux density during the blocking cycle of the respective series connected diode. For this reason, the reactor cores should be of the type having a low residual magnetization wherein small air gaps could be utilized to achieve this end in the absence of special reactor control systems as will be set forth hereinafter.
The first and second branch thus being balanced to carry a substantially equal current within the limits of the magnetizing current of the reactor may then each form a further first and second branch, each of which is taken through a reactor in a manner similar to that described above. The outputs of these two reactors will then have four current branches wherein the current in each of the branches is substantially equal within the limits of the magnetizing current of their controlling reactors.
1f now a single diode is connected in each of the four output branches, then it is clear that they will each carry the same current magnitude differing only by the magnetizing currents of their varying reactors, regardless of their individual forward voltage characteristics.
If it is now desired to further increase the current rating of the system, it is obvious that each of the four output branches could be further subdivided with the use of further balancing reactors whereby eight output branches would be provided at which points diodes would be connected to carry an equally distributed load current.
A second embodiment of the above invention could comprise a simple series reactor connected in series with each of the individual diodes wherein each of the impedances are substantially equal and iixed and are of such a value that the reactor impedance drop is substantially larger than the variations of forward resistance drop between diodes. Hence the variation in forward resistance from diode to diode which results in the current unbalance will be a smaller percentage of the total branch impedance whereby the current unbalance from branch to branch will be reduced similarly and current balancing will result.
The construction of these series reactors is so simple as to possibly offset the disadvantage of decrease in power factor in the rectifier system due to their use. By Way of example, t'ne reactors could be comprised of a substantially U-shaped iron core which is simply slipped over a conductor in series with an associated diode, the air gap between the adjacent ends of the reactor core providing a reactor which will not saturate at peak forward current, and having the desired low residual magnetiza tion to prevent the subsequent saturation of the reactor which would occur since this reactor is subject to repetitive uni-directional pulses. If desired, this U-shaped lamination could be a substantially circular lamination having an air gap cut therein wherein laminations are stacked around the conductor to be connected in series with the diode until the required reactor size is achieved.
In order to provide a more accurate balancing in the above described system with less effect on power factor, using the inexpensive and compact series reactor having only a single turn comprising the main conductor for each diode, each reactor core may be provided with a small secondary winding wherein the secondary windings of each reactor are connected in series to thereby reduce the effective impedance and still force proper current division within the limits of the magnetizing currents of the reactors in a manner similar to that described by the throughstype reactor.
A still further embodiment of the above invention in application Serial No. 628,324, filed December 14, 1956, would be in the utilization of the couplet type reactor used in a chain or cascaded arrangement. More specifically, in the couplet type of system, the conductors of a" first and second diode will be coupled by a magnetic core so that iluxes are induced in the core in opposite directions. The conductor of a third diode is then coupled to the conductor of the second diode by a second magnetic core so that once again lluxes are induced in the second magnetic core in opposite directions by the currents in the second and third diode conductors.
In the same manner, any desired number of conductors which include diodes which are to be connected in parallel may be added to the above noted chain by providing a magnetic core for coupling to adjacent diode conductors so that the fluxes in the core will be induced in opposite directions. So long as the chain arrangement is utilized and the iirst diode conductor is not coupled to the last diode conductor added to the system, the maximum current imbalance between the individual diodes cannot exceed the total magnetizing currents of all the core used minus one.
If, however, an even number of parallel connected diodes are used in the above described chain, it is possible to close the chain by coupling the first and last diode conductor whereby the maximum current imbalance cannot exceed the magnetizing current of one-half the total num ber of reactors. lf it is desired to reduce the current unbalance in the straight chain relationship to the value of one-half the magnetizing current given inherently in the closed chain arrangement, it is possible to close the straight line arrangement even though an even number of parallel elements are utilized by providing an extra core on each end of the straight line arrangement and to thereafter connect auxiliary windings of each core to one another.
As has been pointed out above, it is necessary in each of the above cases to utilize a reactor having a low residual magnetization since the tlux reversing operation on the reactor will be uni-directional and the operation of the reactor will occur somewhere between its point of residual linx density and saturation tlux density. Thus, by providing a low residual magnetization for a low residual 'flux density, the core will be able to achieve a relatively large flux change and may be made relatively small as compared to cores having a relatively high residual magnetization.
It would, however, be desirable to 'utilize a material of the grain oriented type, since magnetizing currents in these type cores is extremely low. il his would normally be prevented, however, since the residual magnetization of these cores is extremely high as compared to the heretofore described cores which could be constructed of normal transformer steel and having air gaps therein.
I have found, however, that l can utilize cores of the highly grain oriented type by providing a first and second core for each reactor wherein the cores are biased to saturation by a D.C. bias in opposite directions.
Thus, if the current ot one common conductor rises, one of the cores will change in flux from a first saturation value to some value below its saturation in the oppo* site direction, while the other core remains saturated.
Conversely, it the current in the other conductor rises, the last mentioned core will experience a iiux change and the first mentioned core will be maintained saturated.
In each case, the cores will be returned to their initial opposite saturations during the inverse voltage portion of the cycle so that they may operate on the successive cycle.
Accordingly, the primary object of this invention is to provide improved reactor means for forcing an equal. current distribution between a plurality of parallel connected 4 diodes wherein the reactor is of the type having a relatively small magnetizing current.
A further object of this invention is to `utilize reactors having double cores of square loop hysteresis material wherein each core is biased to an opposite saturation, the iirst core operating to decrease diode current in a first of a pair of diode conductors, the second core operating to decrease diode current in a second of said pair of diode conductors.
These and other objects of my invention will become apparent from the following description when taken in conjunction with the drawings in which:
Figure 1 shows a single phase halfwave rectifier having a plurality of diodes connected in parallel.
Figure 2 shows the forward voltage characteristics of the diodes of Figure 1.
Figure 3 shows the application of balancing reactors to the circuit of Figure l for forcing a substantially equal current distribution between the diodes.
Figure 4 shows the forward voltage drop on two of' the diodes of Figure 1.
Figure 5 shows another embodiment of balancing type reactors.
Figure 6 shows a still further embodiment of balancing type reactors.
Figure 7 illustrates my novel invention wherein straight-through reactors are applied to the circuit of Figure 1.
Figure 8 is an exploded perspective view showing the mechanical construction of the through-type reactors of Figure 7.
Figure 9 shows the manner in which secondary windings may be applied to the reactors of Figures 7 and 8 for forcing a more nearly equal current balance between their associated diodes while reducing the effect of the reactors on power factor.
Figure 10 shows an application of my novel invention wherein couplet reactors are applied in an open chain relationship.
Figure l1 shows a further application of the couplet type reactors to a closed chain system.
Figure 12 shows how an open chain of couplet reactors for an odd number of diodes may be connected in a closed chain relationship.
Figure 13 shows how an even number of diodes con nected in an open chain by couplet reactors may be connected in a closed chain relationship.
Figure 14 illustrates one possible physical arrangement of an open chain couplet reactor system. Y
Figure l5 shows the bus and bus lianges of the de'- vice of Figure 14.
Figure 16 shows a view of Figure 15 when taken across lines 16-16.
Figure 17 shows a view of Figure 14 when taken across the lines 1717.
Figure 18 shows a View of Figure 14 when taken across the lines 18-18.
Figure 18A shows how the coupling reactors may be modified to allow conductor entrance to the bus of Figure 14 from the same side of the bus rather than from alternate sides.
Figure 18B shows a side View of Figure 18A.
Figure 19 illustrates how the reactors of my novel. invention may be adapted to allow the use of high residual tlux density material having relatively low magnetizing current.
Figure 20 shows the magnetic characteristics of the ever, that the use of a single phase rectifying systemv isv to be taken for illustrative purposes only, since my novel invention is clearly `applicable to any type of rectifier` connection so long as diodes in any branch are to be connected in parallel.
In a similar manner, while the'use of four parallel connected diodes has been used for the most part in the following description, this number has been arbitrarily selected and my novel invention is equally adapted in the paralleling of from two to any desired number of diode elements which are to have a substantially equal current flow therethrough.
Thus, Figure l shows a single phase A.C. voltage source 30 connected to energize a D.C. load 32 through the parallel connected diodes 34, 36, 38 and 40. The forward voltage characteristic of each of diodes 34 through 40 is shown in Figure 2 where it is seen that since each of the diodes of Figure l has a forward voltage drop V1, the current through each parallel branch is diierent. That is to say, diodes 34, 36, 38 and 40 conduct currents having the magnitudes I1, I2, I3 and I4 respectively.
Clearly this unbalance in current distribution is due to the difference in the forward voltage characteristic of each of the diodes as is clearly seen in Figure 2.
The principle of my invention is to provide a reactor control means which is so constructed that the currents in each of the parallel branches will be forced to maintain a substantially equal distribution. Thus, reference to Figure 4 which, for illustrative purposes, shows the wave shapes of the forward voltage drops of the branches containing diodes 34 and 36 of Figure 1 as voltage drops V1 and V2 respectively, these voltage drops are to be controlled by the reactor means of my invention so that an equal current distribution will result. That is to say, the reactor means operating on the current I2 will cause a difference in forward voltage drop for the two diode branches in accordance with the voltage time area which is given by the shaded area of Figure 4, this area being equal to the integral of V1 minus V2 where V2 is the voltage drop on diode 36 times the differential in time. Thus the diode currents may now be adjusted to the same value.
One type of reactor means which satisfies the above condition in accordance with my novel invention is setv forth in Figure 3 wherein the circuitry of Figure 1 has been modified to include the through- type reactors 42, 44 and 46 which are connected in a Whiffle tree type arrangement for forcing the desired current equalization. More specifically, the right hand end of source 30 is broken into a first and second branch which include Windings 48 and 50 respectively on the core 42. These two windings are so connected that they will induce M.M.F.s in the core 42 in opposing directions. Accordingly, as soon as the magnetizing current of core 42 is exceeded because of an unbalance in the ampere turns of the ux due to a higher current in one winding, a voltage will be induced in winding 50 and the voltage in the branch winding will assume a reactance and the current therethrough containing winding 48 will be reduced until the currents in windings 48 and 50 are equal (within the magnetizing current of core 42).
Each of the two branches including windings 48 and 50 are then further branched, the branch including winding 48 being subdivided into branches including windings 52 and 54 while the branch including winding 50 is subdivided into the branches including windings 56 and 58.
Here again current equalization takes place in the branches including windings 52 and 54 and the windings 56 and 58 in the same manner as'previously described for windings 48 and 50. Thus, the current flow through diodes 34, 36, 38 and 40 will be substantially identical, differing only by the magnetization current of the cores acting thereon regardless of their forward voltage characteristics. Hence, if current unbalance would normally exist between the diode branches including diodes 34 and 36, it is lseen that winding 54 will have induced in it a voltage of such a value to alter the 6 voltage drop across diode 36 to a value V2, this voltage drop value being seen in Figure 2 to correspond to the current I1 which is the current flowing through the diode 34. Clearly diodes 38 and 40 will have their voltage drops similarly adjusted to have their current magnitudes equalized to those diodes 34 and 36 through the operation of windings 50 and 58.
Another type of balancing reactor system is set forth in Figure 5 which shows a double Y secondary wherein the yneutral points of the Y connected secondary windings 60 and 62 are connected through an interphase transformer 64, the center of which is connected to one side of 1a load 66. Each phase of secondary windings 60 and 62 is then taken out in the manner substantially identical to that shown in Figure 5 for the case of phase A which is the only phase shown, in order to simplify the diagram.
A multi-legged core (one leg for each rectifier element) is then provided for each of the phases wherein the D.C. component fluxes are cancelled out by having diametrically opposite ph-ases connected through opposing windings. By way of example, phase A of winding 60 is connected to the coils 68, 70 and 72 which are in turn connected in series with rectiers 74, 76 and 78 respectively which then connect to the opposite side of load 66. In a similar manner, phase A is connected to windings 80, 82 and 84 having their associated diodes 86, 88 and respectively similarly connected to load 66.
In order to reduce the overall impedance and its effect on power factor7 and improve voltage distribution, a polygon connected tertiary including windings 92, 94 and 96 is further provided. Clearly each of the three phases of the rectifying system of Figure 5 would be provided with a similar three-legged core as that described in conjunction With phase A.
In operation, the interaction between windings 68, 70 and 72 of the balancing reactor will maintain an equal current distribution between diodes 74, 76 and 78 in the same manner as has been set forth in the case of Figure 3. Similarly, windings 80, 82 and 84 will maintain equal current distribution between their associated diodes 86, 88 and 90 respectively. Because of almost complete cancellation of D.C. ampere-turns, almost the com.- plete flux change can be utilized.
A similar arrangement may be provided for the three phase bridge connected rectifier system of Figure 6 where three parallel diodes are connected in each leg of the bridge. If more than three rectifier elements are connected in parallel, the balancing reactor has more than three legs-one for each element. The tertiary winding is then connected as a regular polygon. In Figure 6 a delta connected secondary winding 9S for energizing a D.C. load has a three-legged core which includes windings 100, 102 and 104 for maintaining equal current distribution through diodes 106, 108 and 110 respectively. Similarly, windings 112, 114 and 116 maintain equal current distribution between diodes 118, 'and 122. Windings 112, 114 and 118 are moved in opposite polarity to windings 100, 102 and 104 to cancel the D.C. ampere turns. Once again, overall impedance is reduced, power factor improved, and voltage distribution is improved by the delta connected tertiary which includes windings 124, 126 and 128.
Clearly my novel invention has been shown in Figure 6 as applied to only one of the phases of secondary winding 98 and the other two phases will be connected in a substantially identical manner.
Figure 7 shows how the circuit of Figure l could be adapted by reactance means of the series connected type. Thus in Figure 7, reactors 130, 132, 134 and 136 are connected in series with diodes 34, 36, 38 and 40. By constructing reactances 130 through 136 so that they will have a substantially higher impedance drop than the resistive drop of their corresponding diodes 34 to 40 and further making the reactance of reactors 130 through 136. a; substantially identical value, thenA the current unbalancewhich isnow controlled by a much higher irripedance will be substantially independent of the diode resistance inthe tforward direction thereby allowing a relatively. greatly. improved current balance between the diode, branches. This system is highly desirable since it lends itself to extremely simple manufacturing techniques.
By way of example, Figure 8 shows that each of the reactors could be comprised of stacks of laminations 138, 140, 142 and 144 which have openings therein 'for allowing the passage of associated diode conductors as well as air gaps such as air gaps 146, 148, 150 and 152 respectively. More specilically, the device of Figure 8 shows the A.-C. source 30 as being connected in series with a. main bus 154 to which conductors 156, 158, 160 and 162 are attached. Each of conductors 156 through 162 is further provided with threaded ends which as will be seen hereinafter cooperate with fastening nuts 164 through 170 respectively. Each of conductors 156 through 162 therefore comprise a single turn winding for the reactor' cores 138 through 144 respectively.
The individual diode assemblies 131i, 132, 134 and 136 are commonly provided with flexible conductors terminated by electrical connecting means 180, 182, 184 and 186 respectively, while their other ends are connected to a second common bus 188 in any desired manner. Accordingly, by inserting conductors 156 through 162 through their respective `reactor cores and corresponding diode terminals 180 through 186 respectively and thereafter tightening nuts 164 through 170 so as to achieve mechanical positioning of the reactors as well as electrical engagement of diode terminals 180 through 186 and conductors 156 through 162, the A.C. source 30 may deliver rectified power to the llt-C. load 32 as indicated in Figure 7. Clearly, the material utilized in coresl 138 through 144 could be in laminated tform or solid form, depending upon yallowable eddy current and hysteresis conditions.
Regardless of the type construction utilized in cores 138 through 144, however, it is necessary that air 146 through 152 respectively be provided (in the absence of auxiliary means which are to be ascribed hereinafter) since it is necessary to avoid sat tion at peak forward currents and to have a small i. .ual 'ilux density within the core `in view of the unidirectional cnergization thereof. That is to say, while the cere is operative, its fiux change occurs only from the point of residual magnetization to a point near saturation magnetization. Hence if as low as possible a residual magnetization is used, the core will be capable of a large flux excursion and would therefore be smaller than one having a small ilux xcursion because of a high residual magnetization.
As noted above, current balance between the various parallel branches in the embodiment of Figure 7 is achieved by making the impedance of reactors 130 through 136 high enough to malte the forward resistance differences of diodes 34- through d@ substantially negligible. It is, however, possible to modify the circuit of Figure 7 so as to force a true current distribution between the parallel connected diodes which is within the limits of the magnetizing currents of the reactors.
This may be accomplished as set forth in Figure 9 wherein the reactor cores 138, 140, 142 and 144 which have air gaps 146, 148, 150 and 152 respectively (see Figure 8) are provided with auxiliary secondary windings 190, 192, 194 and 196 respectively, these secondary windings being connected in series relationship. By this means all the reactors are forced to participate in the correction of a deviation of current in any one rectier element, and there is a great reduction of the ellective impedance of the reactors and their effect on power factor. In view of this connection, the current unbalancebetween any of diodes 34, 36, 38 or 40 is held within the. limits of the magnetizing current of the associated reactors, witlzxouttheundesirableeiectsV of straight reactors.
Figure 10 illustrates still another embodiment ofn'iy novell invention whereincouplet reactors are utilized, forcoupling the individual diode conductorsA of parallel confnected branches. By way of example, Figure 10` spel-ref.. matically illustratesa system of Vparallel connecteddiodes,l wherein conductors 198,200, 202, 204, 2,06, 208,210` and 212 each have a single diode connected` in series, therewith, ThusV the circuit corresponding to the` s chematic illustration of Figure 10.would be similar'. tol'igure, 1 wherein eight rather than four diodes are connected in, parallel and areV to have equalcurrent distributionim.- posed upon parallel connected diodes.
In Figure l0, however, coupled reactors 214, 2,16, 2,18, 220, 222, 224 and 226 couple adjacent'branches oftheI parallel system in such a manner that the currenttlowin, adjacent branches is in opposite directions; as indicated by the dots and crosses ot conductors 198 througlr212y which show current ow into and out of; the drawing respectively.
Thus reactor 214 couples branches 198 and 200 in such, a manner that the fluxes induced in the core 214 due to conductors 198 and 200 are in opposing directions. In aV similar manner, reactor 216 couples branches; 200. and?V 202, reactor 218 couples branches 202 and 204, and soon down the line until the chain is completed by they cou. pling of conductors 210 and 212 by the core- 226.
During operation of a circuit constructed in accord. ance with the circuit of Figure` l0, the current unbalance will not exceed the total magnetizing current of all the cores. minus one, as is obvious in considering thearrange ment.
Here again, cores 214 through 226 should be of mate. rial having a low residual magnetism in order to` preventisaturation of the cores by an accumulation of uni-direc,-v tional volt-seconds in successive conducting periods.
If it is desired, a small air gap may be inserted in` each of the cores to lower its residual magnetism. How. ever, it is possible by auxiliary circuitryto be described; hereinafter', to construct these cores of a grain Oriented material having an extremely low magnetizing cur-rent;y This, of course, would be highly desirable since the maximum current unbalance in the system of Figure 1-0 will be limited to the total magnetizing current of all the cores. minus one, as was set forth above.
In the event that there are an even number of parallel elements in the arrangement of Figure l0, it is. possible to close the loop as shown in Figure 11 by providing the additionalv core 228 which couples conductors 212 and 198. In the closed loop, the maximum current uu. balance is decreased from the case of the straight chain. to the magnetizing current of one-half the total number of reactors. However, in the absence of auxiliary equip.- ment, the loop can only be closed as seen in Figure 11 with an even number of conductors. For if an odd number of conductors were used, the conductors at each end of the chain would conduct current in the same direc.- tion and `could not be directly coupled to one another.
It is, however, possible to close a straight chain of either an odd or even number of conductors by use of auxiliary reactors and auxiliary windings therefor, as set forth in Figures l2 and 1'3. By` way of example, Figure l2 shows the manner in which a parallel group of. con. ductors corresponding to an odd number of diodes may be closed without having to physically circle the configuration. It is to be noted that the configuration of` Figure l2 is substantially identical to that of Figure 10 with the exception of the omission of core 226 and conductor 212.
In order to allow closing of the chain or of the loop, the auxiliary core 230 having an air gap 232 is coupledy to conductor `198 while core 234 having an air gap- 2,36 is coupled to conductorv 210which is the lastgconductolj; oi the.v chain. Each of; cores-'2.30 and 2345 arefthg provided with auxiliary windings 238 and 240 respectively which can be connected to one another in any desired polarity so as to effect closing of the loop by a simple electrical connection which allows any desired choice of configuration of the chain, yet still providing the desired current balance which is limited to only one-half the magnetizing current of all the cores.
. In a similar manner, the configuration of Figure 13 .which is identical to that of Figure may close the loop by means of the same type auxiliary reactors 230 and 234 having auxiliary windings 238 and 240 which are connected as is required to achieve proper polarities of the fluxes in cores 230 and 234 with respect to the flux induced by conductors 198 and 212 respectively.
Here again, however, the coupling of the cores is achieved by purely electrical connecting means rather than by the physical configuration of the core, as was the case in Figure 11.
- Figures 14 through 18 show one method by which the open chain construction of Figure 10 could be accomplished in' a rectifier circuit. Figure 14 shows the A.C. voltage source 30, which is to deliver D.C. power to the load 32 as being connected to a bus bar 242 which, as is best seen in Figures 15 and 16, has conducting flanges 244 and 246 fastened thereto in any desired manner. If desired, the bus may be hollow as shown in Figure 16 to allow passage of a cooling medium. Each of flanges 244 and 246 is provided with alternate through holes and tapped openings so as to allow electrical connection by extensions of conductors 196, 198, 200, 202 and 204 to pass through their corresponding coupling reactors 214, 216, 218 and 220 (see Figure 10) in alternate directions.
Thus the flange plate 244, seen in Figure 15, has a through hole 248, a tapped opening 250, a through hole 252, and then a further tapped opening 254 while ange plate 246 is provided with alternate tapped openings which register with the through hole of flange plate 244 and through holes which register with the tapped openings 250 and 254 of flange plate 244.
Thus, as may be best seen in Figure 17, conductor 198 has a flexible portion fastened to a conducting bolt member 256 which passes through a through hole in flange plate 246 through the balance reactor cores 214 and 216 and thereafter threadably engages flange plate 244 in a current carrying engagement. Conversely, the conductor 200 which was to initiate a flux in core 216 which is in a direction opposite to the flux initiated by conductor 198 passes through hole 248 of flange plate 244 and then through the cores 216 and 218 and terminates in a threaded engagement with flange plate 246. Clearly, this alternate type of construction is continued for each of the current conductors of the particular rectitier phase in question.
Thus, although the rectiers associated with conductors 196, 198, 200 and 202 and 204 which are each connected to the common bus 258 so as to properly energize load 32, the current directions of the conductors of a common coupling reactor are opposite to one another in order to allow the desired current equalization or equal current distribution of current flowing through each of the parallel connected diodes.
If desired, the structure set forth in Figures 14 through 18 may be easily modified so as to allow the conductor entrance through the reactor from the same direction or from the same side of the bus while opposite fluxes may still be induced in the coupling reactors by constructing these reactors to have the figure 8 shape set forth in Figures 18A and 18B. More specilically, Figure 18A shows a coupling core 260 which could be used as any of the coupling cores 214 through 220 of Figure 14 as being constructed of a roll of magnet Wire twisted in a figure 8 shaped and formed to nest in any desired manner as shown in Figure 18B. Clearly, by passing two conductors 262 and 264 through the two openings formed by the ligure 8 as seen in Figure 18A, each having current conduction in Vthe same direction will give rise to opposing fluxes within the core 260. While Figures 18A and 18B show this configuration as being formed by a roll of magnet wire, it could clearly be constructed of punched and formed laminations and could, in fact, be constlucted in any desired manner so long as the residual magnetization is relatively small.
As has been heretofore mentioned, it would be desirable to use a reactor core in any of the above applications of material having as low as possible a magnetizing current since the current unbalance from diode to diode is usually dependent upon this magnitude of magnetizing current. However, it is well known that cores exhibiting very low magnetizing currents such as the square hysteresis loop type of core also exhibit :an extremely high residual flux density. This high residual ux density is extremely undesirable for applications of my novel invention since it would require an extremely large core if the core is to be kept from saturating due to the accumulation of unidirectional energization.
I have found, however, that by forming each reactor of a first and second core of square hysteresis loop material and thereafter biasing each core in an opposite direction, then one core will operate With very low magnetizing current on an ampere turn unbalance in la rst direction while the other core will operate on an ampere turn unbalance in the other direction.
A preferred embodiment of my novel invention using a double core is set forth in Figure 19 wherein a threephase Wye connected transformer winding 270 is to energize a D.C. load 271.
For purposes of clarity, only phase A of the rectier system is shown in Figure 19 and comprises the diodes 272, 274, 276 and 278 and the couplet reactors shown generally by numerals 280, 282 and 284. It is to be noted that reactor 280 couples diodes 272 and 274, reactor 282 couples diodes 274 and 276, `and reactor 284 couples diodes 276 and 278 in a manner similar to that described for the open chain couplet system described hereinabove, this system being chosen for illustrative purposes only.
Each of reactors 280, 282 and 284 are further seen to be comprised of two magnetic cores (which are of square hysteresis loop type material) through Which extends the diode conductors and each having an auxiliary biasing winding. Thus, reactor 280 has a first and second core 286 and 288 which have biasing windings 292 and 290 respectively.
Similarly, reactor 282 is comprised of cores 294 and 296 having biasing windings 300 and 298 respectively while reactor 284 has cores 302 and 304 which have biasing windings 386 and 308 respectively.
Each of the biasing windings 290, 292, 298, 300, 306 and 308 are then connected to a source of biasing potential 310 which caused the two cores of each reactor 280, 282 and 284 to be biased in opposite directions of saturation.
The operation of this novel system may -now be considered for reactor 280 in view of Figure 20 which shows the characteristics of any of the reactors 288, 282 or 284. Assume first that reactor core 286 is biased to the right of the point of Zero current difference between currents through diodes 272 and 274 by D.C. bias energization Nlm of Winding 292 due to bias means 310.
In a like manner, core 288 is oppositely biased by N131() to the left of zero current difference by means of energization of winding 290.
In operation, if the current through diode 272 exceeds that through diode 274, by the amount of Nlm plus the magnetizing current of core 286 then as seen in Figure 20, there will be a positive net difference in ampere turns that will cause reactor core 286 to begin to execute a flux change and therefore decrease the forward voltage on diode 272 and decrease the net current through that parallel branch.
1'1 In asimilar manner, too high a current through diode 274 will cause unsaturation of core 288 which thereby decreases the current in the branch including diode 27 4.
Clearly, reactor 282 operates in the same manner to equalize currents through diodes 274 and 276 while reactor 284 operates on diodes 276 and 278.
Thus it is seen that current equalization proceeds within limits given by the very small magnetizing current of reactors cores 286, 288, 294, 296, 302 and 304.
Although I have here described preferred embodiments of my novel invention, many modifications and variations will now be obvious to those skilled in the art and I prefer therefore to be limited, not by the specilic disclosure herein, but only by the appended claims.
I claim:
1. A current balancing system for a plurality of parallel connected diodes, said current balancing system comprising a reactor means connected in series with each of said parallel connected diodes; said reactor means being constructed to adjust the forward voltage drop on its corresponding diode until the forward currents of each of said diodes are substantially similar regardless of their forward voltage characteristics; each of said reactor means comprising a first and second core of high permeability material, each of said first and second cores being biased in opposite directions.
2. A current balancing system for a first and second parallel connected diode, said current balancing system comprising a first and second reactor winding connected in series with said first and second parallel connected diodes; said reactor windings being constructed to adjust the forward voltage drop on their said corresponding diodes until the forward current through each of said diodes is substantially similar regardless of their forward voltage characteristics; said first and second windings being wound on a first and second common core of square hysteresis loop material in directions to induce opposing fluxes in said cores, `and biasing means for said first and second core, said biasing means being constructed to produce biasing flux in said first core in a first direction and to produce biasing flux in said second core in a second direction.
3. The current balancing system of claim l wherein either said first or second core is capable of iiux change throughout the forward voltage cycle of said diodes.
4. The current balancing system of claim 2 wherein either said first or second core is capable of flux change throughout the forward voltage cycle of said diodes.
5. In a rectifier system for energizing a D.-C. load from an A.C. source, said rectifying system including a plurality of parallel connected diodes for achieving a predetermined current rating, a current balancing system for forcing a substantially equal current distribution between each of said plurality of diodes; said current balancing system comprising inductive means connected in series with each diode of said plurality of diodes; said inductive means being constructed to adjust the forward voltage across each of said diodes to force equal current through each of said diodes regardless of the forward voltage characteristics of said diodes, said induci tive means being operative throughout the forward voltage conduction cycle of said plurality of diodes; said inductive means including a rst and second core and biasing means therefor, for biasing said first core in a first direction and for biasing said second core in a second direction.
6. In a multiphase rectifier system for energizing a D.C. load from a multiphase A.C. source, each phase of said rectifying system including a plurality of parallel connected diodes for achieving a predetermined current rating, a current balancing system for forcing a substantially equal current distribution between each of said plurality of diodes; said current balancing system comprising inductive means connected in series with each diode of said plurality of diodes; said inductive means being constructed to adjust the forward voltage across each of said diodes to force equal current through each of said diodes regardless of the forward voltage characteristics of said diodes, said inductive means being operative throughout the forward voltage conduction cycle of said plurality of diodes; said inductive meansincluding a first and second core and biasing means therefor for biasing said first core in a first direction and for biasing said second core in a second direction.
7. A current balancing system for a plurality of parallel connected diodes, said current balancing system comprising a reactor means connected in series with each of said parallel connected diodes; said reactor means being constructed to adjust the forward voltage drop on its corresponding diode until the forward currents of each of said diodes are substantially similar regardless of their forward voltage characteristics; said reactor means comprising a couplet reactor for magnetically coupling conductors connected to each of said plurality of diodes into pairs; the conductors of each of said pairs being directed to induce opposing fluxes in their respective couplet reactors, each of said couplet reactors having a first and second core biased in a first and second direction.
8. The current balancing system of claim 7 wherein said couplet reactors form a closed chain.
9. The current balancing system of claim 7 wherein said couplet reactors form an open chain having a first and second auxiliary couplet reactor connected to the hrst and last diode conductor respectively of said chain; each of said auxiliary reactors having auxiliary windings thereon connected in series to close the chain.
No references cited.
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US628325A US2891212A (en) | 1956-12-14 | 1956-12-14 | Current balancing transductors for parallel connected diodes |
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US628325A US2891212A (en) | 1956-12-14 | 1956-12-14 | Current balancing transductors for parallel connected diodes |
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Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3018380A (en) * | 1958-10-31 | 1962-01-23 | Westinghouse Electric Corp | Current balancing apparatus |
US3042849A (en) * | 1958-04-03 | 1962-07-03 | Ite Circuit Breaker Ltd | Saturable balancing reactors for rectifier systems |
US3056037A (en) * | 1957-05-27 | 1962-09-25 | Int Rectifier Corp | High-power semi-conductor rectifier |
US3059171A (en) * | 1958-06-06 | 1962-10-16 | Oerlikon Engineering Company | Absorption choke coil, especially for use in high current-intensity rectifier plants |
US3084322A (en) * | 1960-05-02 | 1963-04-02 | Warren Mfg Company Inc | Power rectifying apparatus |
US3085188A (en) * | 1957-03-05 | 1963-04-09 | Siemens Ag | Power-valve reactor, particularly for magnetically controlled power rectifiers |
US3092769A (en) * | 1959-03-30 | 1963-06-04 | Gen Electric | Magnetic amplifier |
US3670236A (en) * | 1970-01-27 | 1972-06-13 | Asea Ab | Converter station having parallel-connected static converters |
US3725769A (en) * | 1972-01-10 | 1973-04-03 | Gen Electric | Digital regulator and method of current regulation |
US3943426A (en) * | 1973-09-25 | 1976-03-09 | Siemens Akteiengesellschaft | Thyristor column |
EP2782234A1 (en) * | 2013-03-22 | 2014-09-24 | Kabushiki Kaisha Toshiba | Rectifier and method for controlling the same |
-
1956
- 1956-12-14 US US628325A patent/US2891212A/en not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
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None * |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3085188A (en) * | 1957-03-05 | 1963-04-09 | Siemens Ag | Power-valve reactor, particularly for magnetically controlled power rectifiers |
US3056037A (en) * | 1957-05-27 | 1962-09-25 | Int Rectifier Corp | High-power semi-conductor rectifier |
US3042849A (en) * | 1958-04-03 | 1962-07-03 | Ite Circuit Breaker Ltd | Saturable balancing reactors for rectifier systems |
US3059171A (en) * | 1958-06-06 | 1962-10-16 | Oerlikon Engineering Company | Absorption choke coil, especially for use in high current-intensity rectifier plants |
US3018380A (en) * | 1958-10-31 | 1962-01-23 | Westinghouse Electric Corp | Current balancing apparatus |
US3092769A (en) * | 1959-03-30 | 1963-06-04 | Gen Electric | Magnetic amplifier |
US3084322A (en) * | 1960-05-02 | 1963-04-02 | Warren Mfg Company Inc | Power rectifying apparatus |
US3670236A (en) * | 1970-01-27 | 1972-06-13 | Asea Ab | Converter station having parallel-connected static converters |
US3725769A (en) * | 1972-01-10 | 1973-04-03 | Gen Electric | Digital regulator and method of current regulation |
US3943426A (en) * | 1973-09-25 | 1976-03-09 | Siemens Akteiengesellschaft | Thyristor column |
EP2782234A1 (en) * | 2013-03-22 | 2014-09-24 | Kabushiki Kaisha Toshiba | Rectifier and method for controlling the same |
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