US2675520A - Tap changing under load apparatus with current dividing means - Google Patents

Description

2 Sheets-Sheet l w. c. SEALEY TAP CHANGING UNDER LOAD APPARATUS WITH CURRENT DIVIDING MEANS 21, 1951 April 13, 1954 Filed Dec.

Apnl 13, 1954 w. c. SEALEY TAP CHANGING UNDER LOAD APPARATUS WITH CURRENT' DIVIDING MEANS 2 Sheets-Sheet 2 Filed Dec. 21 1951 Patented Apr. 13, 1954 TAP CHANGING UNDER LOAD APPARATUS WITH CURRENT DIVIDING MEANS William G. Sealey, Wauwatosa, Wis., assignorto Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application December 21, 1951-, Serial No. 262,869

9 Claims. 1

This invention relates to voltage regulating systems including regulating transformers having tap changing apparatus designed for operation while the regulating transformer is under load. The invention is particularly related to improvements in the tap changing circuit for such regulating transformers.

The tap changing under load apparatus" of voltage regulating transformers are a considerable factor in the determination of the maximum ratings for which such transformers can be designed, and may even bethe determining factor of the maximum rating. Because the switching appartus of such tap changersmust operate under load there are practical limitations on their current ratings, and these limitations therefore also affected the size and rating of the regulating transformers.

In this invention the current rating of the tap changing apparatus is considerably increased independently of the type of regulating transformer or the type of tap changing apparatus of the regulator. While the invention is adaptable to and described with relation to regulators embodying dial switch tap changingapparatus, it is not limited to such apparatus- An improved circuit is provided which will considerably increase the rating of the tap changing apparatus; and consequently some of the limitations imposed on regulating transformers by their tapchanging apparatus may be avoided. This invention is directed to an under load voltage regulating transformer provided with current dividing means whereby the current rating of the-tap changing apparatus is increased.

It is an object of the present invention. to provide improved voltage regulating systems hav ing tap changing under loadapparatus.

Another object of the present invention is to increase the maximum ratings of the. tap changing apparatus of voltage regulating systems without having to increase the current ratings of the individual current carrying elements-of thetap changing apparatus.

Still another object of this invention is. .to provide under load voltage regulating transformers which have both full and half cycle step regulation and in which the current carried or interrupted by the tap changing apparatus is equally divided to a plurality of tap changers in all regulating positions.

Still another object is to provide. an improved tap changing apparatus forunder load voltage regulators in which the. current load is evenly divided to at least four current interrupting switching contacts of tap changers,in the full and the half cycle tap changing positions, with substantially even step regulation throughout the range of the regulator.

Objects and advantages other than-those above set forth will be apparent from a consideration of the following descriptionwhen read'in connection with the accompanying drawings in which:

Fig. 1 is a diagram of a circuit for voltage regu-' lating equipment arranged in'accordance with this invention and-shown-in a full tap position;

Fig. 2 is a diagram of a modification of part of the circuit illustrated in Fig.1;

Fig. 3 is a view in elevation of a modification of the physical arrangementof thev switching contacts of the tap changer illustrated in-Fig. 1, with part of the switch shownin section;

Fig. 4 is a diagrammatic illustration of the tap changer in a fullcycle position; and

Fig; 5 isa diagrammatic illustration of the-tap changer in a half'cycle position.

The voltage regulating equipment shown in Fig. 1, includes an excitingwinding l l for-a voltage -.-regulator which may be used to maintain the voltage'of a load circuit at a substantially constant value independently of changes in the load. The regulator is connected between a source of .supplycurrent 6, 1 and a loadcircuit 8, 9. Regulation of the'load circuit is accomplished by adding voltage to the load circuit or subtracting voltage therefrom by changingthe position of a-load 'line lead 9 at equally spaced taps l2 to l9, inclusive, of the winding 1 I. The tapped winding H of the regulator may be made in. separate sections and include a reversing switch (not shown) so that the winding may be made to either buck or boost the exciting winding voltage of. the source to regulate the voltage in the load circuit. In orderto improve the rating. of the step type regulating transformer. there is provided a means for positivelydividingthe load current to at least four switching contacts of. the tap changing apparatus with equal division of the current beingassured in the full and the half cycle regulating positions.

In the illustrated embodiment, the regulator has a plurality of connections at eachtap of the winding ll. Each of the connections has the same arrangement of similar components. Anexamplebeing the connection attap M which has as its components tap M, a parallelingreactor .24, and first and second stationary contacts 31', 32. The tap I4 is electrically. connected to a midtap of the reactor 24, and the terminals of the reactor 24 are electrically connected to the stationary contacts 3| and 32, respectively, of a dial switch 30.

The paralleling reactors may each be wound on its own core as shown in Fig. 1 or may all be wound on only two cores 53, 54 as shown in Fig. 2. When only two cores are provided, the windings of the paralleling reactors associated with alternate taps are all on one of the two cores While the windings of the paralleling reactors associated with the intermediate taps are all on the other of the two cores. In either case the windings of paralleling reactors connected to adjacent taps are not wound on the same core so that the regulator may have tap bridging, half cycle regulating positions.

In Fig. 1 the stationary contacts are mounted in two radially spaced circular rows or sets on an insulating panel 31, and the contacts in each row or of each set are circumferentially spaced from each other. While the stationary contacts are illustrated in Fig. 1 as mounted in two radially spaced circular rows, the two rows of contacts arranged as shown in Fig. 3 so that a pair of presently available dial switches may be utilized for the tap changing operation without any considerable changes to the dial switches. The dial switches shown in Fig. 3 are arranged back to back with the conductors to the contacts located between the two dial switches.

Dial switch 30 has four moving contacts 33, 34, 35, 36, each of which preferably includes the con- 'ventional pair of wiper blades which brush opposite sides of the stationary contacts. A first pair 33, 34 of the moving contacts engage one set of the stationary contacts, in this instance, the contacts of the inner row of Fig. 1; and a second pair 35, 36 of the moving contacts engage the other set of stationary contacts, the outer row of Fig. 1. The moving contacts 33 and 35 are respectively circumferentially spaced from the moving contacts 34 and 36; and this spacing is coordinated with the spacing between the stationary contacts and the circumferential length of the stationary contacts so that the two pairs of movable contacts, 33, 34 and 35, 36, respectively, can bridge adjacent fixed contacts in the inner and outer rows for half cycle positions and may also be stopped on a single stationary contact in their respective rows for a full cycle position.

' The operation of the dial switch mechanism as regards the moving contacts and stationary contacts therefore is conventional of dial switch tap changers and provides both the full and half cycle tap positions. The four moving contacts in this instance operate as a unit and preferably are moved substantially simultaneously although only two of the movable contacts, such as 34, 36, move from one fixed contact to an adjacent fixed contact during a tap change stop. It is not necessary, however, that the four movable contacts all be moved simultaneously nor is it necessary that the tap changer be a dial switch, as cam operated contactors may be utilized for changing taps. The tap changer in the preferred embodiment utilizes conventional dial switch mechanism including a motor 48 and driving gear mechanism 46 which can be operated in either of two directions by a switch 49 which connects a source 4'! to the motor. Operation of the motor in one direction raises the regulated load voltage, while the operation of the motor in the other direction lowers the voltage of the load circuit. Conventional control mechanism may be provided for 4 the motor for energizing the motor circuit responsive to voltage changes of the load circuit.

A modification of the dial switch shown in Fig. 1 is illustrated in Fig. 3. Dial switch 6| comprises an insulating panel 62 upon which are mounted stationary contacts, such as 63, 64. These contacts are connected to terminals of the various paralleling reactors by means of conductors which are carried through the top member of casing 60 in a gang bushing 56. One movable contact 66 is connected through brush 6! to a collector ring 68 and the other movable contact (not shown in Fig. 3) is connected through brush G9 to collector ring 10.

The movable contacts of the dial switch are carried by an insulating member 65 attached to shaft 59 for movement across the stationary contacts. In this modification a second dial switch H has an operating shaft 58 connected by a shaft coupling 51 to shaft 59 of dial switch 6|. Conductors are brought through the gang bushing 56 to stationary contacts l3, 14 which are mounted on insulating panel 12. Shaft 58 has attached thereto an insulating member 15 which carries a pair of movable contacts and their associated brushes and collector rings; collector ring 18 and brush H are connected to movable contact 16, and collector ring and brush [9 are connected to a movable contact which is not shown.

The under load regulator illustrated includes the single set of interlocked circuit breakers 85, 86 which is operated by suitable means (not shown) and which is coordinated with the movement of movable contacts of the tap changer in a well known manner. Circuit breaker opens before contacts 33, 35 are moved from one fixed contact to an adjacent fixed contact and closes after that movement of those contacts is completed, and circuit breaker 86 opens before the contacts 34, 36 are moved from one fixed contact to an adjacent fixed contact and close after that movement of those contacts is completed. The circuit breakers are interlocked and never both open at the same time during operation of the regulator.

The movable contacts of the dial switch shown in Fig. 1 are each connected to collector rings 38, 39 of conducting material. In the arrangement represented in Fig. 1, the two movable contacts 33, 35 may be connected in parallel to a single collector ring 39, and the other two movable contacts 34, 36 may be connected in parallel to a second, single collector ring 38, although with two pairs of presently available dial switches shown in Fig. 3 four collector rings may be utilized by connecting a single collector ring with each movable contact.

The two collector rings shown in Fig. 1 are electrically connected through the single set of circuit breakers 85, 86 to the terminals of a current dividing preventive autotransforrner 44, with lead 9 of the load circuit connected to the midtap 45 of the autotransformer. The circuit connections which have been described place the preventiv autotransformer between the contacts of both pairs of movable contacts. The autotransformer 44 is connected in circuit with the paralleling reactors to effect the division of load current so that each movable contact need only carry one fourth of the load current. The preventive autotransformer is also connected between the contact of each pair of the movable contacts toeffect the transitionfrom a full to-halr cycleposition Particular advantages ofthe regulator which have been described will be evident from aconsideration of theaction of the regulator when in the full or half cycle positions. Irrespective of Whether the regulator is in one or the other of those positions, the load current will properly and evenly divide between the four movable contacts because of midtap autotransformer current dividing action.

For example, in the full cycle position represented in Fig. 4 with the four movable contacts atone tap position [4, the load current is divided by the preventive autotransformer 44 so that the current in the collector rings 38, 39 will be equal. A second division of the current is effected by the circuit. between the collector rings and: the taps of the winding, and the current of each movable contact is one fourth the load current. In this circuit collector ring 38 is connected to movable contacts 34, 36 which respectively make contact with stationary contacts 3 l 32 which are respectively connected to the two terminals of reactor 24. And collector ring 39 is connected to movable contacts 33, 35 which respectively make contact with stationary contacts 3|, 32 which are respectively connected to the two terminals of reactor 24, and the midtap of reactor 24 is connected to tap IA of the winding.

Similar division of the load current between the movable contacts is assured in the bridging or half cycle position illustrated in Fig. 5. Again the current at each collector ring 38, 39 will be onehalf of the load current because of the midtapped preventive autotransformer 44. The midtap reactor 24 will effect equal division of current between the stationary contacts 3| and 32, and the reactor 25 which has its midtap connected to tap l5, will effect equal division of current between the stationary contacts 5| and 52 which are connected to the terminals of reactor 25. The combination of the four movable contacts with the midtap reactors and with the midtapped preventive autotransformer assures the equal division of current in the half cycle positions as well a in the full cycle positions.

The embodiment of this invention in under load voltage regulators. makes it possible to utilize tap changer apparatus on voltage regulating transformers of considerably increased size without requirin complicated switch systems or control circuits for operating the tap changer apparatus of the equipment. Where the size of the regulator is not increased the current carried by individual contacts of the tap changing apparatus may be considerably reduced.

For regulators having a set of circuit breakers for interrupting the load current, as illustrated in the drawing, the rating of the regulator can be doubled. without a corresponding increase in the cost of theequipment evenxthough two of the dial switches are utilized instead of one. That is possible because there is need for only a single set of the conventionally interlocked circuit breakers and a single autotransformer bothof which would normally be embodied in a conventional step type regulator. The cost of the additional parallelin reactors for 's'uchan improved regulator would reduce the savings effected only very slightly as those paralleling reactors are very inexpensive compared to the savings effected by doubling the rating of regulator without adding an additional set of the circuit breakers or a second autotransformer.

Further, the embodiment of this invention-in step type regulators not only reduces'the'current load on the dial switches, but the current dividing circuit provided for that purpose will not cause uneven steps of regulation.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in th art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired tosecure by Letters Patent:

1. A voltage regulating system comprising a Winding having a plurality of spaced taps; a pair of dial switches including first and second pairs of movable contacts, first and second sets of spaced stationary contacts, and mean for substantially simultaneously moving said first and second pairs of movable contacts across said first and second sets of stationary contacts, respectively; a plurality of paralleling reactors, each of the stationary contacts of said first set being connected to a corresponding contact of said second set through one of said paralleling reactors, each of said paralleling reactors having its midtap connected to one of said taps, and a midtap autotransi'ormer common to said dial switches, one movable contact of each of said pairs of movable contacts connected to one terminal of said autotransformer, and the other movable contact of each of said pairs of movable contacts connected to the other terminal of said autotransformer, the midtap of said autotransformer constituting a terminal of said system.

2. In a voltage regulating system, the combination of an autotransformer having a midtap constituting a terminal to be connected to a load circuit, a transformer winding having a plurality of connections; each of said connections comprising a tap of said winding, a first stationary contact, a second stationary contact, and a paralleling reactor having terminals connected to said stationary contacts and having a midtap connected to said tap of said transformer winding; a first pair of movable contacts severally connected to the terminals of said autotransformer, a second pair of movable contacts connected in parallel with said first pair of movable contacts, and means for simultaneously moving said first pair of movable contacts across said first stationary contacts and said second pair of movable contacts across said second stationary contacts.

3. A voltage regulating system including a tapped winding, a tap changing under loadapparatus comprising a pair of half cycling tap changers each having a plurality of switching elements, first current dividing means electrically connected between said tap changers and taps of said winding, and a second current dividing means electrically connected between pairs of said switching elements of each of said tap changers and including an autotransformer having a midtap constituting a terminal lead connection of said system.

4. A voltage regulating system having a winding with a plurality of connections; each of said connections comprising a tap of said winding, a first stationary contact, a second stationary contact, and a paralleling reactor, said reactor having terminals connected to said stationary contacts and a midtap connected to said tap of said winding; a first pair of said movable contacts, a second pair of movable contacts, tap changing mechanism for substantially simultaneously moving said first pair of movable contacts across said first stationary contacts and said second pair of movable contacts across said second stationary contacts, and a current dividing means connected between the contacts of each of said pairs of movable contacts.

5. A voltage regulating system including a transformer having a winding with a plurality of connections; each of said connections comprising a tap of said winding, a first stationary contact, a second stationary contact, and a paralleling reactor, said reactor having terminals connected to said stationary contacts and a midtap connected to said tap; first and second pairs of movable contacts respectively cooperable with said first and said second stationary contacts, means for simultaneously moving each of said pairs of movable contacts across their respective cooperable stationary contacts, and a midtap autotransformer, one contact of each of said pairs of movable contacts connected to one terminal of said autotransformer, the other contact of each of said pairs of movable contacts connected to the other terminal of said autotransformer, the midtap of said autotransformer constituting a terminal of said system.

6. A voltage regulator including a transformer having a winding with a plurality of connections; each of said connections comprising a tap of said winding, a first stationary contact, a second stationary contact, and a paralleling reactor, said reactor having terminals connected to said stationary contacts and a midta connected to said tap; first and second pairs of movable contacts respectively cooperable with said first and said second stationary contacts, means for simultaneously moving each of said pairs of movable contacts across their respective cooperable stationary contacts, a midtap autotransformer, a first circuit connecting one contact of each of said pairs of movable contacts to one terminal of said autotransformer, and a second circuit connecting the other contact of each of said pair of movable contacts to the other terminal of said autotransformer, the midtap of said autotransformer constituting a terminal of said regulator, and a pair of interlocked circuit breakers, one of said breakers in said first circuit and the other of said breakers in said second circuit.

7. A voltage regulating system comprising a winding having a plurality of spaced taps; a pair of dial switches including first and second pairs of movable contacts, first and second sets of spaced stationary contacts, and means for substantially simultaneously moving said first and second pairs of movable contacts across said first and second sets of stationary contacts, respectively; a plurality of paralleling reactors, each of the stationary contacts of said first set being connected to a corresponding contact of said second set through one of said paralleling reactors, each of said paralleling reactors having its midtap connected to one of said taps, and a midtap autotransformer common to each of said dial switches, a first circuit having one movable contact of each of said pairs of movable contacts connected to one terminal of said autotransformer, a second circuit having the other movable contact of each of said pairs of movable contacts connected to the other terminal of said autotransformer, the midtap of said autotransformer constituting a terminal of said system. and a pair of interlocked circuit breakers, one of said circuit breakers in said first circuit and one of said breakers in said second circuit.

8. A voltage regulating system including switching means, a transformer having a winding with a plurality of connections; each of said connections comprising a tap of said winding. a first contact and a second contact of said switching means, and a paralleling reactor, said first contact being connected to said second contact through said paralleling reactor, said paralleling reactor having a midtap connected to a tap of said winding; a midtapped autotransformer, a first plurality of circuits connected in parallel to one terminal of said autotransformer, a second plurality of circuits connected in parallel to the other terminal of said autotransformer, said switching means selectively connecting two circuits of said first plurality of circuits to first and second contacts of one of said connections and connecting two circuits of said second plurality of circuits to first and second contacts of said one connection or connecting two circuits of said first plurality of circuits to first and second contacts of said one connection and connecting two circuits of said second plurality of circuits to first and second contacts of a connection adjacent said one connection.

9. A voltage regulating system including a winding provided with taps, a first tap changer having a first switching element and a second switching element, a second tap changer having a first switching element and a second switching element, first current dividing means electrically connected to each of said taps of said winding, means for connecting said first elements of said two tap changers selectively to each of said taps of said winding through said first current dividing means and for connecting said second elements of said two tap changers selectively to each of said taps of said winding through said first current dividing means, a second current dividing means connected to a terminal of said system, and circuit means connecting said second current dividing means to said first and second elements of said first tap changer and connecting said second current dividing means to said first and second elements of said second tap changer, said circuit means including a first circuit breaker connected between said second current dividing means and said first elements of said two tap changers, said circuit means including a second circuit breaker connected between said second current dividing means and said second elements of said two tap changers, said first and second circuit breakers being interlocked to prevent both of said circuit breakers being opened at the same time.

References Cited in the file of this patent UNITED STATES PATENTS Number

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