GB2167581A - Transformer control circuit - Google Patents
Transformer control circuit Download PDFInfo
- Publication number
- GB2167581A GB2167581A GB08427677A GB8427677A GB2167581A GB 2167581 A GB2167581 A GB 2167581A GB 08427677 A GB08427677 A GB 08427677A GB 8427677 A GB8427677 A GB 8427677A GB 2167581 A GB2167581 A GB 2167581A
- Authority
- GB
- United Kingdom
- Prior art keywords
- control
- assembly
- winding
- output
- transformer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P13/00—Arrangements for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output
- H02P13/12—Arrangements for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output by varying magnetic bias
-
- 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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M5/25—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M5/257—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
-
- 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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Electrical Variables (AREA)
Abstract
An electrical controller for controlling a transformer without using mechanical tap-changing means includes a control winding (13), the current in which is varied by means of a circuit (17) acting in dependence upon the output of measuring means (19) which measures the voltage across or the power factor of the primary (11) or secondary (12) coils. The output of the measuring means (19) is fed to a square-wave generator (21) whose mark-space ratio is arranged to be dependent upon the measured value. The output is supplied to the control circuit (17), for example to the bases of transistors (22). Thyristors connected in reverse parallel may also be used. A three-phase version is also described. The transistors (22) may be continuously controlled rather than switched. The winding (13) couples reactive elements (16, 26) to the transformer. <IMAGE>
Description
SPECIFICATION
Transformer controller
This invention relates to a controller for controlling a distribution or other transformer, and one object is to provide means for correcting transformer output voltage regulation, and/or possibly overall power factor, without having to use the conventional complicated tap changing gear, or power factor correcting step control switch gear.
Another object of the invention is to provide an automatic controller for a distribution, or other transformer, using, primarily, solid state components without moving parts.
According to the present invention, a transformer controller comprises a control winding on the transformer in addition to primary and secondary windings, and a control circuit, responsive to a parameter of the seconary winding output under load, for controlling current flow in the control winding.
Frequently, regulation of a distribution transformer output voltage is due to the reactive nature of the load and, for such an application, the control circuit can include capacitors which, when connected in circuit with the control winding, draw capacitive current, which can have the effect of both improving the power factor and, at least partially, compensating for voltage regulation. The degree to which the capacitance is connected in the control winding circuit can depend upon the detected secondary winding output voltage, or, perhaps, the secondary or primary winding power factor.
The control circuit may include semi-conductor devices, for example, transistors or thyristors, for controlling the current flow in the control winding.
In one example, transistors are included and the current level in the control winding circuit will depend upon the detected parameter of the transformer secondary winding output, perhaps, by controlling the bias on the transistor base, perhaps by use of a specially shaped control voltage.
In another form of the invention, using one or more transistors in a part of the control circuit on the d.c. side of a rectifier, a square wave, or ON/OFF, generator can be controlled by the parameter detector to vary the mark-to-space ratio of the generated square wave, which is used to switch the transistor on and off cyclically. The greater the transformer secondary regulation, the greater will be the markto-space ratio of the square wave, and the greater the average current in the capacitive, or other, control winding circuit. It is equally possible to use thyristors, perhaps, connected on reverse parallel pairs, with the firing angles to their gates controlled from the output of the parameter detector.
The ON/OFF wave frequency is preferably very large compared with the supply frequency in that ripple due to switching can be readily smoothed out.
The d.c. side of the rectifier would generally include a smoothing circuit sufficient not only for d.c. operation of the power transistors, but also to minimise the ripple effect at the primary and secondary winding terminals to maintain a high degree of sine wave purity of the supply frequency.
Either way, control can be automatic in response to regulation, or even in response to the overall power factor detected at the primary winding or load power factor at the secondary winding, and without having moving parts, but relying essentially on semi-conductor devices.
The invention may be carried into practice in various ways, and one embodiment will now be described, by way of example, with reference to the accompanying drawings of which Figure 1 is a circuit diagram of a transformer regulation controller utilizing power transistors, and applied to a single phase supply;
Figure 2 is a circuit diagram of a transformer regulation controller utilizing power transistors, and applied to a three phase supply;
Figure 3 is a vector diagram showing current and voltage vector relationships in the primary and secondary winding of the transformer;
Figure 4 is a vector diagram showing regulated current and voltage vector relationships in the primary and resultant of secondary load and control windings of the transformer;
Figure 5 is a circuit diagram of a single phase transformer regulator controller utilizing thyristors.
A distribution transformer (10) has a primary winding (11), energised from the high-voltage supply; a second winding (12) and a control winding (13).
Secondary winding (12) has output terminals (14) from which the various loads (15) on a distribution network are supplied, and a feature of the invention is a means for compensating for regulation of the output voltage (V2) across the terminals (14) under load, without using tap changing gear.
For that purpose, the control winding (13), which supplies a capacitor load (16), is arranged to be intermittently connected in the circuit by use of a control circuit (17), which responds to an input signal at (18) from a voltage-sensitive device (19), connected across the teminals (14).
The control signal (18), which is dependent on, and preferably proportional to the voltage (V2) across the terminals (14), controls the mark-to-space ratio of a square wave generator (21), whose square wave output is applied to the bases of a number of parallel connected transistors (22) in the control circuit (17). The circuit of the control winding (13) includes the AC side of a full wave rectifier (23) whose DC side is connected to a smoothing circuit, a typical smoothing circuit includes a choke (24) with parallel capacitors (25) across the emitter/collector terminals of the transistors (22). Where transistors are connected in parallel the circuitry includes components such as resistors (26) to provide load sharing between transistors.
The reactive circuit controlled by the powertran- sistor may require suppression (snubber) circuitry similar to that shown in U.K. Patent No.1525924.
The switching speeds of the square wave control signal would be chosen to satisfy the rating characteristics of the power transistors and could be in the range of 50 Fsec to 2.5 Fsec or more (e.g. 20,000 to 400,000 times per sec) or any switching speed that presents negligible ripple effect at the sine wave of the supply frequency.
During the marks of the square wave from the generator (21), the transistors pass current and effectively close the ci rcuit via the rectifier (23) of the control winding (13) through the capacitor (16) so that capacitive current is drawn in that circuit. During the spaces in the square wave, the transistors will be off and the control winding (13) will be effectively open circuited.
Alternatively, the capacitor current can be varied by the magnitude of the powertransistor base current and so vary the magnitude of each switched square wave of the collector/emitter current.
In some applications, a choke (26) is connected across the control winding (13) with an inductive reactance high compared with the capacitive reactance against over-voltage and reduce the secondary voltage if the supply voltage is high and operation is at light load.
For the sake of clarity Figures 1 and 2 do not include protective devices and switch gears or circuit breakers to satisfy recognised good practice.
Figure 3 shows the conventional vector diagram for a transformer, having primary and secondary windings, in which the secondary winding supplies an inductive load so that the secondary current (12) lags the secondary voltage (V2).
In the control circuit, including the capacitor (16), is open circuited because the mark-to-space ratio of the square wave is zero, then operation is just as indicated in Figure 3 but, if the mark-to-space ratio is large, so that the capacitor is effectively continuously connected in the control circuit, the control circuit will draw a capacitive current, and the effect will be to couple a leading current into the secondary load circuit, so that the vector diagram, relating the same quantities as shown in Figure 3, will now be the same as shown in Figure 4. It can be seen from
Figure 4 that the effect of the leading secondary current enables the secondary voltage (V2) to be increased, as compared with Figure 3, to be at least equal to the secondary EMF (E2).The mark-to-space ratio of the square wave is continuously varied in dependence on the measured voltage (V2), as described above, and that determines the portion of each square wave cycle during which the capacitor (16) is in circuit, so that the control is progressive.
Thus, the more the voltage (V2) drops, the greater will be the mark-to-space ratio of the square wave, and the longer time per square wave cycle the greater the capacitor current flowing in the control circuit, until the regulated secondary voltage is at the desired value. In this way, variation of the reactive load (15) across the secondary of the distribution transformer can be continuously automatically compensated for, using semi-conductor components with no moving parts.
Figure 2 shows an arrangement very similar to
Figure 1, except that the invention is applied to a 3-phase transformer, having a 3-phase primary winding (31), a 3-phase secondary winding (32) and a 3-phase control winding (33). The detected voltage for controlling the mark-to-space ratio of the square wave generator (21) is derived across two phases of the secondary winding (32), as indicated at 34. The smoothing arrangement (24) is similar two that in
Figure 1, and the rectifier bank (36) provides full wave, 3-phase rectification. There is an individual capacitor (37) in each line of the 3-phase control winding (33).
An alternative circuit to the circuit of Figure 1 but using thyristors (41) instead ofthe transistors (22) is shown in Figure 5. The thyristors can be seen to be connected in reverse parallel in the control winding circuit, including the capacitor (16) and the optional reactor (26). The controller (21) time base circuitry relative to the supply frequency (e.g. 50Hz) and its conductive firing angle responds to the feed back reference from the output of the voltage-sensitive device (19), and results in advancing or retarding the firing angle applied to the gate electrodes of the respective thyristors, so that they are both conducting during their respective half cycles of operation.
The effect on the transformer characteristics will be the same as with the circuit of Figure 1, and the vector diagram will be as in Figure 4. Acceptable suppressor equipment recognised for limiting the harmonic current created by thyristor half cycle switching into the supply network is not shown.
Mathematical models and tests show that, by use of the control winding circuit in accordance with the invention, the regulation of the secondary output voltage due to reactive load, can be over or under compensated relative to the secondary nominal voltage when providing optimum power factor operation, while the increased copper and iron losses and heat dissipation losses, due to the presence of the control winding circuit, are, in total, no more than the winding losses arising from conventional distribution transformer tap changing gear. The control of secondary output voltage regulation is achieved with an accompanying improvement in the resultant overall transformer and load power factor, and so is capable of decreasing the KVA demand and increase on KW output available relative to the transformer KVA rating.
One simple possible form for the detector (19) comprises a small step-down isolating transformer reducing the AC output voltage to, perhaps, 12 volts
AC, feeding a full wave rectifier and an averaging network, consisting of solid state components, the output of which can be compared with a reference
DC voltage to produce the error signal at 18. The reference voltage can have manual adjustment means for setting in accordance with requirements.
As described above, in the circuit of Figure 1,the square wave control signal will be used to turn the transistors (22) on or off. It is also possible to provide a variable continuous (not switched) drive to the base to control the current level in the transistors.
One example is an approximation to a halfinverted sine wave, the removal of sharp corners from such a wave can mean that snubber circuits can be avoided.
The circuit might not use the full rated transistor current, but should have the advantage discussed above.
In alternative arrangements, the control signal at 18 could be derived, not in proportion to the secondary output voltage (V2), but rather to the primary or secondary power factor by using detec tors responsive to voltage and current, and an appropriate combining circuit.
It will, of course, be appreciated that any of the transistors and thyristors could be connected in series, series parallel, or parallel banks, if the demands of rhe circuit required it.
Claims (20)
1. Atransformer controller comprising a control winding on the transformer in addition to primary and secondary windings, and a control circuit, responsive to a parameter of the secondary winding output under load or to the primary winding power factor, for controlling current flow in the control winding.
2. A controller as claimed in Claim 1 in which the parameter is the secondary winding voltage.
3. A controller as claimed in Claim 1 in which the parameter is the secondary winding power factor.
4. A controller as claimed in Claim 1 or Claim 2 or
Claim 3 in which the control circuit is composed substantially of solid state components.
5. A transformer assembly comprising a transformer having primary, secondary and control windings, means for sensing a parameter of the secondary winding output under load or the primary winding power factor and control means for controlling current flow in the control winding in dependence on the sensed parameter.
6. An assembly as claimed in Claim 5 in which the parameter is the secondary winding voltage.
7. An assembly as claimed in Claim 5 in which the parameter is the secondary winding power factor.
8. An assembly as claimed in Claim 5 or Claim 6 or Claim 7 in which the control means comprises a control circuit composed substantially of solid-state components.
9. An assembly as claimed in any of Claims 5 to 8 in which the control means includes a square-wave generator adapted to produce a mark-space ratio dependent upon the output of the sensing means, and the current in the control winding being arranged to be varied in response to the output of the square-wave generator.
10. An assembly as claimed in Claim 9 in which the control means includes a solid state on-off switch arranged to operate in response to the output of the square-wave generator and repeatedly to open-circuit the control winding.
11. An assembly as claimed in Claim 9 or Claim 10 in which the control means includes a transistor, the current in the control winding being varied by means of the square-wave generator output being applied to the transistor base.
12. An assembly as claimed in Claim 9 or Claim 10 in which the control means includes a thyristor, the current in the control winding being varied by means of the square-wave generator output being applied to the thyristor gate.
13. An assembly as claimed in Claim 12 in which the control means includes two thyristors connected in reverse parallel, the square-wave generator output being applied to both their gates.
14. An assembly as claimed in any one of Claims 5 to 13 in which the control winding, when connected, is arranged to provide a capacitative load.
15. An assembly as claimed in any one of claims 5to 14 including an inductor connected across the control winding.
16. An assembly as claimed in any one of Claims 5 to 15 in which the sensing means includes a step-down transformer and a rectifier.
17. An assembly as claimed in Claim 16 including means for producing a reference DC voltage, means for comparing the DC voltage with the rectifier output and for producing an error signal, being the output of the sensing means, representative thereof.
18. An assembly as claimed in any one of the preceding claims in which the primary, secondary and control windings are three phase windings.
19. An assembly as claimed in Claim 18 in which the secondary winding voltage or power factor is derived across two phases of the secondary winding.
20. A transformer assembly substantially as specifically herein described with reference to Figures 1 and 4, or Figures 5 and 4 or Figure 2 of the accompanying diagrams.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08427677A GB2167581B (en) | 1984-11-01 | 1984-11-01 | Transformer control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08427677A GB2167581B (en) | 1984-11-01 | 1984-11-01 | Transformer control circuit |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8427677D0 GB8427677D0 (en) | 1984-12-05 |
| GB2167581A true GB2167581A (en) | 1986-05-29 |
| GB2167581B GB2167581B (en) | 1987-12-09 |
Family
ID=10569109
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08427677A Expired GB2167581B (en) | 1984-11-01 | 1984-11-01 | Transformer control circuit |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2167581B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102946225A (en) * | 2012-10-18 | 2013-02-27 | 中国兵器工业集团第二一四研究所苏州研发中心 | Exciting circuit for rotating transformer |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1178003A (en) * | 1966-02-28 | 1970-01-14 | Int Standard Electric Corp | Improvements in or relating to Magnetic Regulators |
| GB1497238A (en) * | 1975-04-21 | 1978-01-05 | Burroughs Corp | High efficiency power supply having a reactive buck automatic dc voltage regulator |
| GB2033163A (en) * | 1978-10-14 | 1980-05-14 | Tdk Electronics Co Ltd | Variable leakage transformers |
| GB2048528A (en) * | 1979-04-12 | 1980-12-10 | Sony Corp | Voltage regulators |
| GB2094520A (en) * | 1981-02-26 | 1982-09-15 | Data General Corp | Power supply regulator |
-
1984
- 1984-11-01 GB GB08427677A patent/GB2167581B/en not_active Expired
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1178003A (en) * | 1966-02-28 | 1970-01-14 | Int Standard Electric Corp | Improvements in or relating to Magnetic Regulators |
| GB1497238A (en) * | 1975-04-21 | 1978-01-05 | Burroughs Corp | High efficiency power supply having a reactive buck automatic dc voltage regulator |
| GB2033163A (en) * | 1978-10-14 | 1980-05-14 | Tdk Electronics Co Ltd | Variable leakage transformers |
| GB2048528A (en) * | 1979-04-12 | 1980-12-10 | Sony Corp | Voltage regulators |
| GB2094520A (en) * | 1981-02-26 | 1982-09-15 | Data General Corp | Power supply regulator |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102946225A (en) * | 2012-10-18 | 2013-02-27 | 中国兵器工业集团第二一四研究所苏州研发中心 | Exciting circuit for rotating transformer |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8427677D0 (en) | 1984-12-05 |
| GB2167581B (en) | 1987-12-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19991101 |