US2947837A

US2947837A - Reversing switch for load tap changing transformer

Info

Publication number: US2947837A
Application number: US608576A
Authority: US
Inventors: Alfred H Baguhn
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1956-09-07
Filing date: 1956-09-07
Publication date: 1960-08-02
Anticipated expiration: 1977-08-02

Description

Filed Sept. 7, 1956 H BAGUHN 2,947,837

A. REVERSING SWITCH FOR LOAD TAP CHANGING TRANSFORMER 2 Sheets-Sheet 1 4 9M K5: Whammy Aug. 2, 1960 A. H. BAGUHN 2,947,837

REVERSING SWITCH FOR LOAD TAP CHANGING TRANSFORMER Filed Sept. 7, 1956 2 Sheets-Sheet 2 C I I Tl- REVERSING SWITCH FOR LOAD TAP CHANGING TRANSFORMER Alfred H. Baguhn, West Allis, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Sept. 7, 1956, Ser. No. 608,576

4 Claims. (Cl. 200-92) This invention relates in general to step type voltage regulating apparatus and in particular to an improved reversing switch assembly for such apparatus.

Step type voltage regulating apparatus are used extensively in electrical distribution systems where it is desired to maintain the voltage of a circuit between predetermined limits. Most apparatus of this type comprises an exciting winding connected across the circuit to be regulated, and a tapped series winding connected in series with the circuit through a load tap changing mechanism. The load tap changing mechanism includes a tap changing switch having a plurality of stationary contacts connected respectively to the taps on the series winding, and movable contacts which cooperate with the stationary contacts to insert diiierent portions of the series windings in the circuit to be regulated.

In order to employ the same series winding and tap changing mechanism to effect a change in voltage both above and below normal, the load tap changing mechanism usually includes a reversing switch assembly which is operable to reverse the connections of the tapped winding of the regulator with respect to the circuit to be regulated. Most reversing switches include a pair of contacts connected respectively to opposite ends of the series winding and a third contact member connected to a supply terminal of the regulator. In a first position of the reversing switch one end of the series winding is connected to the supply terminal, and in a second position of the switch the other end of the series winding is connected to the terminal. The reversing switch thus resembles a single pole double throw switch.

In order to operate the reversing switch from one position to the other when it is not carrying current, a camming arrangement is employed between the load tap changing mechanism and the reversing switch assembly which causes the reversing switch to move when the movable contacts of the tap changing switch are at the zero tap position of the regulator.

The switching action of the reversing switch usually starts prior to the switching of the movable contacts of the tap changer from the Zero tap position to insure that the reversing switch is suitably positioned prior to completion of the tap changing operation to either side of the zero tap.

In known prior art apparatus of the above type no provision is made to return the reversing switch to its original starting position in the event that a tap changing operation from the zero tap to an adjacent tap is started but not completed. For example, it often happens that in regulating the voltage of a load circuit the tap changer is on the zero tap position when the control circuit for the regulator calls for a tap change. The motor which operates the tap changing mechanism is then energized and a tap changing operation is started which through a camming arrangement starts to move the reversing switch. If at some time prior to the time that the movable contacts of the tap changer are actually moved, the tap hired States Patent changing motor is deenergized by the control circuit because conditions in the load circuit have corrected themselves, the movable member of the reversing switch is disposed somewhere between the two stationary contacts of the reversing switch. It is thus possible for areing to occur between the movable member and the stationary contacts of the reversing switch due to the fact that a charge is built up on the series winding under these conditions. This arcing results in radio and television interference in addition to shortening the life of the reversing switch contacts.

In accordance with the present invention the above mentioned disadvantages of prior art regulators are eliminated by providing a reversing switch assembly in which the movable member of the switch is caused to return to its initial position in the event the tap changing operation from the zero tap is not completed.

It is therefore an object of the present invention to provide an improved reversing switch assembly for a step type voltage regulator.

A further object of the present invention is to provide in a step type voltage regulator, a reversing switch assembly which returns the switch to its initial position in the event the switching operation is started but not completed.

Objects and advantages other than those mentioned above will be apparent from the following description when read in connection with the drawings in which:

Fig. 1 is a diagrammatic illustration of a step type voltage regulating apparatus;

Fig. 2 is a front view in elevation of the tap changing mechanism for the step type regulator shown in Fig. 1;

Fig. 3 is a side view in elevation of the tap changing mechanism shown in Fig. 1;

Fig. 4 is an isometric view of the improved reversing switch assembly shown in Figs. 2 and 3; and

Figs. 5, 6 and 7 illustrate the operation of the reversing switch assembly shown in Fig. 4.

Referring to the drawing and particularly to Fig. 1 the step regulator illustrated therein comprises generally an exciting winding 11, a series winding 12 which is provided with a plurality of taps 13, a load tap changing mechanism 14 for connecting various portions of winding 12 in the circuit 15, and a reversing switch assembly 16 which operates to connect either end 17 or end 18 of winding 12 to supply terminal 19 of the regulator.

As shown in Fig. l exciting winding 11 is adapted to be connected across a circuit to be regulated and series winding 12 is adapted to be connected in series with the circuit to be regulated, the windings being inductively related by means of a magnetic core 20. As is well known, the voltage of the circuit 15 is varied in steps by operation of theload tap changing mechanism 14, the reversing switch assembly 16 of mechanism 14, being employed to eifect variations in voltage either below or above the voltage supplied to exciting winding 11. While the illustrated embodiment shows the series winding 12 provided with taps, it should be understood that other suitable arrangements of the windings and taps known in the art may be employed with the improved reversing switch assembly 16, Fig. 1 being merely illustrative of one type of regulating apparatus in which the present invention may be advantageously employed.

As shown in Figs. 2 and 3 the load tap changing mechanism 14 comprises generally a dial type tap changing switch 22 and a quick break mechanism 23. Tap changing switch 22 comprises a plurality of circumferentially spaced stationary contacts 24 and a pair of movable contacts 25a and 25b. The stationary contacts 24 are mounted on an insulating panel 26 and connected respectively to taps 13 of series winding 12, except for the zero tap contact 24' which is connected to terminal 19 of the regulator.

ing relationship with respect to adjacent stationary contacts 24. Movable contacts 25 are connected to the circuit 15 through a midtap reactor 27.

Shaft 28 and movable contacts 25 are moved in steps with a snap action by means of quick break mechanism 23. Quick break mechanism 23 comprises generally a stationary index plate 29, a drive sprocket 30, an actuating disk 31, a detent means 32, and a latch device 33 which is fixedly attached to the actuating disk 31 and engageable with a notch 34 in the stationary index plate 29. A crank like member 35 links the actuating disk 31 to the shaft 28 of tap changing switch 22.

Detent means 32 as shown comprises a pair of

spring assemblies

36a and 36b which are disposed between the drive sprocket 30 and the actuating disk 31. Each spring assembly 36 is connected between the drive sprocket 30 and the actuating disk 31 by means of pin members 37. Quick break mechanism 23 is driven by motor 38 through a chain 39, motor 38 being energized by means of a suitable condition responsive control circuit (not shown) associated with the circuit 15 connected to the load terminals of the regulator.

The reversing switch assembly 16 comprises generally the reversing switch 40 and a rocker assembly 41 to actuate switch 40 in accordance with the movement of the tap changing switch 22. Reversing switch 40 as shown comprises three arcuately spaced

fixed contacts

42, 43 and 44 and a pair of movable contacts 45.

Contacts

42 and 44 are connected respectively to opposite ends of series winding :12 while contact 43 is connected to source terminal 19 of the regulator. Movable contacts 45 of switch 40 operate in one position to connect end 17 of Winding 12 to the supply terminal 19 of the regulator, and in the other position to connect end 18 to the supply terminal 19.

Movable contacts 45 are fixedly attached to a shaft 46 which is suitably positioned in insulating panel 26 on which

stationary contacts

42, 43 and 44 are suitably mounted. Contacts of the reversing switch 40 are pivoted from one position to the other by means of rocker assembly 41. Rocker assembly 41 shown in detail in Fig. 4 includes a member 50 which is pivotally mounted on the vertical mounting panel 51 of the quick break mechanism 23, and a second member 52 which is attached to member 50 by cross arms 53. Member 50 is provided with a recessed portion 54 for receiving a cam pin 55 attached to the drive sprocket 30. Member 52 is provided with as lot 56 for receiving a connecting pin 57 extending from the movable portion of the reversing switch 40. Connecting pin 57 functions to transmit the pivotal movement of assembly 41 to switch 40. Pin 55 is disposed on the sprocket 30 and functions with slot 54 as a cam so that rocker assembly 41 is forced to pivot about a shaft 58 at the start of the tap changing operation which is to move the movable contacts 25 of the tap changer 22 from the zero tap position 24.

The reversing switch assembly 16 further includes means for causing rocker assembly 41 to return to either of tWo positions. This means as shown comprises a pair of spring assemblies 60. The spring assemblies 60 are disposed diametrically opposite to each other with respect to the axis of shaft 58 about which rocker assembly pivots. Each spring assembly 60 comprises a spring guide tube 61 fixed at one end 62 to the drive member 50, and provided with an elongated slot 63 for receiving a pin element 64 secured to the mounting frame 51 of the quick break mechanism 23. A compression spring 65 is disposed in the guide tube 61 and acts between the drive member 56 and the pin element 64 to urge rocker assembly 41 to either of two extreme Positions when the cam pin 55 attached to sprocket member 30 is not in engagement with the side portion of the recess 54. If desired, additional springs may be disposed between the pin 64 and the outside and of the guide tube 61 to reduce noise during operation of the switch.

Assuming that the movable contacts 25 of the tap changing switch 22 are on the zero tap position 24 as shown in Figs. 1, 2 and 3, and that the rocker assembly 41 is in the position shown in Figs. 2, 3 and, 5, the operation of the regulating apparatus from the zero tap position is substantially as follows. 7

Motor 38 is suitably energized by the control circuit (not shown) in response to a condition of circuit 15. Motor 38 is energized presumably so that sprocket member 30 rotates counterclockwise as shown in Fig. 2. R0- tation of sprocket 30 causes cam pin 55 to move rocker assembly 41 from the position shown in Fig. 5 to that shown in Fig. 6. Rotation of sprocket 30 also causes spring assemblies 36a of detent means 32 to become biased. Energy from motor 38 is stored in biasing means 32 because one end of assembly 36a is fixed to actuating disk 31 which is kept from moving by latch device 33, while the other end of assembly 36a is fixed to the sprocket 30. Latch device 33 is arranged so that it does not release until the rocker assembly 41 is substantially on the center position illustrated in Fig. 6.

If motor 38 remains energized so that the tap change from the zero tap 24 is completed, rocker assembly 41 is moved to the position shown in Fig. 7. The movable contacts 45 of reversing switch 40 are operated by means of pin 57, as shown in Fig. 4.

However, if motor 38 is deenergized prior to the time rocker assembly 41 reaches an over center position which corresponds to the tripping time for latch device 33, the detent means 32 returns the sprocket 30 toward its initial starting position, allowing the spring assemblies 60 to move rocker assembly 41 back to its original starting position.

It will thus be seen that the movable contacts 45 of the reversing switch 40 are always in either of two extreme positions and cannot float between the

stationary contacts

42, 44 in the event a tap changing operation is started but not completed.

While only one embodiment of the present invention has been illustrated and described it will be apparent to those skilled in the art that modification may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

1. A reversing switch assembly for a quick break load tap changer comprising a two position reversing switch mounted on a shaft, a rocker assembly pivotally mounted on a frame of a tap changer, said rocker assembly being engageable at a point removed from its pivot by a pin carried in an are by a relatively slow moving motor driven element of said tap changer to pivot said rocker assembly between positions corresponding to the positions of-said reversing switch preparatoryto the quick break operation of the tap changing switch, said switch shaft engaged with said rocker assembly for transmitting the pivotal movement of said rocker assembly to said switch, and toggle means cooperating with opposite sides of said rocker assembly and urging said rocker assembly toward one of said positions after a predetermined pivotal movement of said rocker assembly and urging said rocker assembly toward the other of said positions to positively position said reversing switch independently of the tap changer motor in the event that said motor is d'eenergized before said rocker assembly reaches said predetermined position.

2. A reversing switch assembly for a quick break load tap changer comprising a reversing switch mounted on a shaft and having two positions each corresponding to one of two operating ranges of the tap changer. a rocker as embly :pivotally mounted on a frame of the tap changer, said rocker assembly being engageable at a point removed from its pivot by a pin carried in an are by a relatively slow moving motor driven element of the tap changer to pivot said rocker assembly from a first position corresponding to one of said ranges to a second position corresponding to the other of said ranges preparatory to the snap operation of the tap changing switch from a Zero position into one of said operating ranges, said switch shaft engaged with said rocker assembly for transmitting the pivotal movement of said rocker assembly to said switch, and pair of spring means urging said rocker assembly to one of said positions to snap operate said reversing switch after a pivotal movement of said rocker to a predetermined point and to return said reversing switch to its initial position in event that the motor of said tap changer is deenergized before said rocker assembly reaches said predetermined position.

3. A reversing switch assembly for a quick break load tap changing transformer comprising a reversing switch having a pair of fixed contacts and a movable contact mounted on a shaft for making contact with one of said fixed contacts, a rocker assembly pivotally mounted on a frame of a tap changer, said rocker assembly having a recess removed from its pivot for receiving a pin carried by a relatively slow moving motor driven element of said tap changer to pivot said rocker assembly, preparatory to a quick break movement of the tap changing switch, from an operating position associated with said movable contact of said reversing switch to an operating position associated with one of said fixed contacts, said switch shaft engaged with said rocker assembly for transmitting the pivotal movement of said rocker assembly to said reversing switch, and biasing means cooperating with 6 diametrically opposed sides of said rocker assembly and urging said rocker assembly to one of its two positions to positively position said reversing switch independently of the operation of said tap changer.

4. A reversing switch assembly for a quick break tap changing transformer comprising a reversing switch having a pair of fixed contacts and a movable contact mounted on a shaft, a rocker assembly pivotally mounted on a frame of the tap changer, said rocker assembly having a recess removed from its pivot for receiving a pin carried by a relatively slow rotating motor driven element of the tap changer to pivot said rocker from a first position to a second position, said switch shaft engaged with said rocker assembly for transmitting the pivotal movement of said rocker assembly to said reversing switch, and a pair of springs cooperating with diametrically opposed sides of said rocker to snap said reversing switch rapidly to one of said fixed contacts after a predetermined pivotal movement of said rocker and to restore said reversing switch to the other of said fixed contacts in event that the tap changing motor is deenergized before said rocker assembly completes said predetermined pivotal movement.

References Cited in the file of this patent UNITED STATES PATENTS 2,177,109 Hill Oct. 24, 1939 2,253,183 Le Count Aug. 14, 1941 2,560,002 Sealey July 10, 1951 2,679,563 Katsumata May 25, 1954 2,774,830 Sealey Dec. 18, 1956 2,779,899 Lennox Jan. 29, 1957 2,791,648 Maloney May 7, 1957