Patent GB-207198-A (GB)
Title: Improvements in and relating to automatic control equipments for electric rotary converters
IPC: H02K47/08
Filed: 1923-11-17
Abstract: 207,198. British Thomson-Houston Co., Ltd., (Assignees of Whiting, M. A.). Nov. 17, 1922, [Convention date]. Systems for conversion, employing rotary converters.-An automatic control system for a rotary converter includes switching-means for connecting the converter to the alternating-current source, means for subsequently connecting the field ending of the converter to a source of direct current, and means operated by the current thus supplied to the field winding for connecting the latter across the direct-current brushes of the converter. The converter is started by closing the switch 20, which completes the circuit of the coil 21 of a master relay 22. The closing of the contacts 31 of the relay completes the circuit of the coil 32 of the starting contactor 6, which thereupon closes and connects the slip rings 2 of the converter to low-voltage taps on a transformer 5. At the same time, the motor 38 of a motor generator set is connected to the control circuit 23 through contacts 37 on the contactor 6. During the starting process all but two of the direct-current brushes 8 of the converter are raised from the commutator; the two remaining brushes being connected in circuit with the winding 41 of a relay 40. When the converter is at or near synchronism, this relay operates to close contacts 42 in the circuit of the coil 44 of a contactor 15 which connects the field winding 12 of the converter to the generator 13 through the coil 48 of a relay 46. When the converter is in synchronism and of the correct polarity, the relay 46 opens its contacts 45 and closes contacts 49, thereby disconnecting the field winding from the generator 13 and connecting it across the brushes 8 through the contactor 16 and the coil 51 of a relay 34 which responds to a predetermined value of direct current. When the field current reaches this value, the relay 34 operates to disconnect the slip rings 2 from the lowvoltage taps and to complete the circuit of the coil 54 of the contactor 7 which closes and connects the slip rings to the full voltage of the transformer. At the same time the circuit of the motor 38 is broken at the contacts 37 of the contactor 6 and the motor-generator set shuts down. The circuit of the motor 10 controlling the brush raising and lowering mechanism is completed at contacts 56 of the contactor 7, and the movable brushes 8 are lowered on to the commutator, the circuit of the motor being broken by a limit switch 10<1> at the close of the operation. One set of the brushes 8 is connected to earth and the other set is connected to the distribution circuit 4 through a contactor 9, controlled by a voltageequalizing relay 56<1> and a polarized relay 59, when the voltage on the direct-current side of the converter is of sufficient magnitude and of correct polarity. The relays 40, 46 are of the " hesitating " type, i.e. when their coils are de-energized they do not open their circuits immediately and are therefore unaffected by momentary disturbances during the switching operations. The shutting down of the converter is effected by de-energizing the coil 21 of the master relay 22, either by opening the switch 20 or bv the operation of the usual protective devices indicated at 26, 27.