Patent GB-329736-A (GB)
Title: Improvements in or relating to control and voltage regulating means for electrical transforming devices
IPC: G05D3/16
Filed: 1929-03-09
Abstract: 329,736. General Electric Co., Ltd., and Angola, A. E. March 9, 1929. Systems depending on static transformers.-In a system comprising a number of transformers adapted to work in parallel, the voltage regulating means of each transformer is associated with a selector switch and arrangements whereby, when an inoperative transformer is to be brought into operation, the associated switch is automatically brought into a position corresponding to the position of the regulating means of an operative transformer, and causes the regulating means of the incoming transformer to assume the same position. The selector switches 2 each comprise contacts 5, 6, 7 carried by the cam shafts of the tap-changing gear which may be of the type described in Specification 329,425, the contacts 6 co-operating with interconnected sets of studs 3. Each set of studs also co-operates with a bridge carried by an arm 9 rotatable independently of the contacts 5, 6, 7. The arm 9 of the inoperative unit (No. 1) to be brought into operation is caused to rotate to a position corresponding to the position of the regulator of the operative unit (No. 2) indicated by the position of the contact 6 of the corresponding switch by the following sequence of operations. Switch 19 is placed in the "parallel" position to close contacts 49. Button 17 of No. 1 unit is pressed thus energizing (from auxiliary supply 1, 4) the closing coil 18 of contactor 15 which comprises contacts 46, 47, 48 arranged respectively in the circuits of the " forward " and " reverse " contactors of the motor operating the tap changing gear and the circuit of the contactor of the motor operating the main switch 16 of No. 1 unit. The contactor 15 is maintained closed by a retaining circuit completed at contacts 45. The contacts 45 also complete the circuit of a coil 54 through contacts 44 associated with main switch 16 of No. 2 unit and contacts 41 associated with main switch 16 of No. 1 unit. This circuit is alternately made and broken by contacts 56 associated with an opening coil 24 periodically energized by closing of contacts 25 by an oscillating arm 59 influenced by the coil 54 and a spring 61. Oscillation of the arm 59 causes, through pawl and ratchet gear 12, step-wise rotation of the arm 9. Thus the bridge is caused to traverse the studs 3 until it arrives at a stud corresponding to that upon which the contact 6 of No. 2 unit rests, whereupon either the " forward " or the " reverse " contactor of the motor operating the tap-changing gear is energized through conductors 71 or 76 according to whether the bridge is resting on contact 5 or contact 7, the circuits being completed through the conductor 29 connecting the studs 3. At the same time, a second opening coil 23 associated with the contacts 56 is energized, thus maintaining open the circuit of the coil 54 and preventing further actuation of the arm 9. The motor operating the tap-changing gear proceeds to raise or lower the voltage of the incoming transformer by rotation of the cam shaft carrying the contacts 5, 6, 7 until the contact 6 arrives at the stud 3 upon which the bridge is resting, at which point the circuit of the forward " or " reverse " contactor is broken at the contacts 5, 7. At the same time, the circuit of the contactor of the motor operating the main switch 16, indicated by conductor 74, is completed through the contacts 6 of both units which now rest on the pair of studs 3 connected by the conductor 29. The motor then operates to switch in No. 1 unit. Switching in of this unit when No. 2 unit is inoperative is made possible by the provision of contacts 42 on the main switch 16 which serve to complete the circuit (indicated by conductor 73) of a trip coil de-energization of which trips the main switch 16. Similarly No. 1 unit is maintained operative in the event of No. 2 unit being tripped out of circuit by the fact that the circuit of the trip coil associated with No. 1 unit is maintained by contacts 43 on it own main switch 16 although the contacts 43 on the other switch have been opened. Specification 324,460, [Class 38 (ii), Electric currents, Converting &c.], also is referred to.