US2675519A

US2675519A - Tap changing under load apparatus with paralleling reactors common to all taps

Info

Publication number: US2675519A
Application number: US262785A
Authority: US
Inventors: Louis C Aicher
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1951-12-21
Filing date: 1951-12-21
Publication date: 1954-04-13
Anticipated expiration: 1971-04-13

Description

April 13, 1954 L. TAP CHANGING UNDER LOAD APPARATUS WITH .PARALLELING c. AICHER 2,675,519

REACTORS COMMON TO ALL TAPS Filed Dec. 21 1951 Patented Apr. 13, 1954 TAP CHANGING UNDER LOAD APPARATUS WITH PARALLELING REACTORS COMMON TO ALL TAPS Louis C. Aicher, Elm Grove, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application December 21, 1951, Serial N 0. 262,785

3 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. Because the switching apparatus of such tap changers must operate under load there are a practical limitations on their current ratings, and

these limitations therefore affected the size and rating of the regulating transformers.

The invention hereinafter described comprises a new under load voltage regulating system in which 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 associated with the regulator. While the invention is adaptable to and described with relation to regulators embodying dial switch tap changing apparatus, it is not limited to such apparatus.

It is an object or" the present invention to provide a circuit for reducing the current carried by the contacts of tap changer apparatu of step type voltage regulators.

Another object of this invention is to provide an improved relatively inexpensive circuit for step type under load voltage regulators having minimum current carried by the individual elements of the tap changing apparatus.

Still another object of this invention is to reduce the cost and number of component parts of a current dividing circuit for the tap changing apparatus of voltage regulators having full and half cycle step regulation.

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

Fig. 1 is a diagram of a circuit for step type voltage regulator embodying this invention, with the regulator shown in a full cycle position; and

Fig. 2 is a diagram of the tap changer in a half cycle position.

The voltage regulator illustrated in the drawing is a step type regulating transformer usable for maintaining the voltage of a loadcircuit 8, 9 at a constant value independently of changes in the load. In this instance, the regulator includes ace-43.5)

an exciting winding II which as a plurality of spaced taps I 2 to ill and dial type under load tap changing equipment 30 with which the load circuit is regulated by changing the position of load line lead or regulator terminal 9 at the spaced taps of the winding ll. Operation of the dial switch tap changing equipment to is accomplished through driving gears 29 by motor 48, which can be caused to operate in either of two directions by a switch 49 connecting the motor to its source ll. Operation of the motor in one direction raises the load voltage, and operation of the motor in the other direction lowers the load voltage. mechanism (not shown) may be provided so that the switch 49 responds to voltage changes of the load circuit.

The dial switch tap changer equipment illustrated includes two pair of movable contacts, a first pair 33, as and a

second pair

35, 36. These contacts preferably are all moved substantially simultaneously by a common means including the motor 43 and its gear drive 29.

The dial switch of course includes an insulating board 31 on which are mounted circumferentially spaced fixed contacts 2!, 3| and 22, 32. One pair of the movable contacts 35, 3G, is shown as being radially spaced from the other pair 34. The fixed contacts are illustrated as being arranged in pairs, such as 2!, 22, to provide two sets of fixed contacts which are either radially or axially spaced. Contacts 2|, 22 are electrically connected to each other and to tap it of the winding. The other pairs of fixed contacts are likewise electrically connected together and to taps of the winding.

Circuit means is provided for the tap changing equipment so that between any two of the movable contacts there is a current dividing means and also so that between the contacts of each pair of movable contacts there is a preventive auto-transformer for effecting the transition from full to half cycle positions and for limiting the circulating current which would otherwise result when the movable contacts are in a half cycle or bridging position.

The circuit means referred to comprises the four

movable contact

33, 34, 35, 36, respectively, which are associated through brushes with

collector rings

44, 2, 43, 4|. Those collector rings are connected to terminals of two

paralleling reactors

55, 56, which places a paralleling reactor between a movable contact of each of the pairs of movable contacts. Movable contact 33 is connected through collector ring 44 and con- Conventional, automatic control I ductor H to one terminal of reactor 55, and movable contact 35 is connected through collector ring 43 and conductor 12 to the other terminal of reactor 55. Movable contact 34 is connected through collector ring 42 and conductor '13 to one terminal of reactor 58 and movable contact 35 is connected through collector ring ll and conductor 14 to the other terminal of reactor 55. Thus, the reactors provide current division between a contact of one pair of movable contacts and a contact of the other pair of movable contacts.

In addition, a current dividing means is provided between the two contacts of each of the pairs of movable contacts. In view of the fact that the pairs of movable contacts must bridge adjacent fixed contacts in every other regulating postion, the current division is accomplished in this instance by a single preventive autotransformer 51 which also is utilized to make efiective the half cycle positions by preventing the short circuiting of the winding between the bridged taps at a half cycle position of the regulator.

One terminal of the preventive autotransformer 51 is connected to midtap 65 of reactor 55 through circuit breaker 61 and the other terminal of the preventive autotransformer 51 is connected to midtap 66 of reactor 56 through circuit breaker B8. The connection to the midtap of the reactors assures that equal current division will be efiected between the

movable contacts

33, 35 and 34, 36 by

reactors

55 and 56, respectively. In order to provide current division between the contacts of each of the pairs of movable contacts by the preventive autotransformer, it has a midtap which constitutes a terminal 9 of the regulator.

Positive current division. between the movable contacts is achieved in either a full or a half cycle position of the regulator. Fig. 1 illustrates a full cycle position in which the regulator terminal is connected to the midtap of the preventive autotransformer so that the load current divides equally between the two halves of that autotransformer and at the midtaps of reactors 55,

56. Each of those midtapped reactors provides equal parallel. current division between the movable contacts through parallel circuits.

In the half cycle position shown in Fig. 2 the autotransformer and the reactors also eifect current division of one-fourth load current in each of the movable contacts in the same manner as for the full cycle position since the arrangement of the midtapped reactors is not altered.

Since a circuit arranged according to this invention for under load regulators includes only a single preventive autotransformer, a single set of circuit breakers and only one pair of paralleling reactors, the cost of doubling the rating of the regulator is relatively low.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in the 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 to secure by Letters Patent:

1. A voltage regulating system comprising a of movable contacts connected to the other terminal of said second reactor, one terminal of said autotransformer connected to the midtap of said first reactor and the other terminal of said autotransformer connected to the midtap of said second reactor, the midtap of said autotransformer constituting a terminal of said system.

2. A voltage regulating system comprising a winding having a plurality of spaced fixed contacts, a first pair of spaced movable contacts, a second pair of spaced movable contacts, means for moving said movable contacts across said fixed contacts, each of said pairs of contacts cooperating with said fixed contacts to provide full and half cycle switch positions, a first reactor, a second reactor, and a preventive autotransformer, one contact of said first pair of movable contacts connected to one terminal of said first reactor and one contact of said second pair of movable contacts connected to the other terminal of said first reactor, the other contact of said first pair of movable contacts connected to one terminal of said second reactor and the other contact of said second pair of movable contacts connected to the other terminal of said second reactor, said preventive autotransformer providing current dividing means between the movable contacts and effecting the transition from full to half cycle regulating positions by having one of its terminals connected to the midtap of said first reactor and the other of its terminals connected to the midtap of said second reactor and having its midtap constituting a terminal of said system.

3. A voltage regulating system comprising a transformer with a winding having a plurality of taps and tap changing apparatus including first and second pairs of movable contacts, a plurality of fixed contacts, a terminal of said system, and a plurality of midtapped reactors connected between said movable contacts and said terminal, the midtap of a first of said reactors constituting said terminal, the midtap of a second of said reactors connected to one terminal of said first reactor and the midtap of a third of said reactors connected to the other terminal of said first reactor, the four contacts of said first and second pairs movable contacts severally connected to the four terminals of said second and third reactors, said fixed contacts severally connected to said taps, and means for substantially simultaneously moving said movable contacts across said fixed contacts to change the position of said terminal with respect to said taps.

References Cited in the file of this patent Electrical Engineering, October 1942, vol. 61, pages 727732 relied on.