Patent GB-437763-A (GB)
Title: Improvements in means for effecting regenerative control of electric motors
IPC: H02P3/06
Filed: 1934-06-19
Abstract: 437,763. Master control of D.C. motors; actuating controllers. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and CROFT, E. H., c /o General Electric Co., Witton, Birmingham. June 19, 1934, No. 18154. [Class 38 (iii)] Regenerative braking; varying E.M.E.- A controller 2 is arranged to be moved in one direction from an initial motoring position a to control motoring, and in the opposite direction from an initial regenerative position n to control regeneration, power operating means being provided for effecting relatively slow movement in the one direction or the other, or relatively rapid movement from an initial position to the other initial position, or from an intermediate position to one or the other of the initial positions. The relatively slow motoring and regenerative control movements are effected by electromagnetically-controlled and pneumatically-operated pawl and ratchet mechanisms 3, 5, while the rapid movements to the initial positions a and n respectively, are effected by electromagnetically-controlled and pneumatically-operated pistons 13, 15. The invention is described as applied to a regenerative control system employing a booster as described in Specification 432,754. When a reversing switch 96 is moved to an operative position, coils F1W, F7W, B1W, B2W, are energized to connect the booster driving motor to the supply and close the circuit of the field of the booster so that the latter generates a voltage in opposition to the supply. Series resistances in the circuit of the booster driving motor are cut out by contactors S1W, S2W, connected across the booster 69 in series with appropriate resistances 134, 135. Upon operation of a master controller 1 to a shunt position B, a reverser is operated under control of a coil 94 or 95, and a valve coil 17 is energized to cause the piston 13 to operate the controller 2 to its initial motoring position a, in which position a line switch coil LS1W and a motoring contactor coil MW are energized. Thus the main motor circuit is completed and the driving motors operate at shunting speed. If the master controller 1 is then operated to half or full speed positions C or D, the controller 2 is operated to positions h or n, by the corresponding pawl and ratchet mechanism 3. Cam-operated switches 33-41 are thereby actuated to control the booster voltage in magnitude and direction and accelerate the main motors to half or full speed. If the master controller 1 is moved to the brake position F, the coil G2W of a regenerating contactor is energized and the main motor field windings are connected to an exciter in series with a stabilizing resistance. The valve coil 17 of the regenerating off cylinder 16 is also energized and the controller 2 is moved to the initial regenerating position n, in which position a circuit for the unlatch coil 56a of a voltage balance relay 52 is completed, and the relay 52 is released and floats in a neutral position with contacts 56 closed. The contacts 56 complete a circuit for the coil 49 of a regenerating relay which closes maintaining contacts 53, and contacts 54 in the circuit of the coil 11 governing the regenerating pawl 5. The regenerating relay also de-energizes the coil 17 of the regenerating off cylinder 16, and the controller is then ratcheted from its initial regenerating position n. The booster field is thus controlled in a sequence reverse to that for motoring, and when the motor and line voltages balance, the relay 52 closes its contacts 60 to complete circuits for coils G1W, LS1W, of contactors which complete the regenerative connections to the line. The flow of regenerated current operates a cut-out relay 61 which de-energizes the motor voltage winding of the relay 52, energizes its latch coil 55, and maintains the circuits of the coils LS1W and G1W over contacts 57 of the relay 52 closed by the energization of its latch coil 55. If the master controller 1 is moved to a brake hold position E, the action of the regenerative panel 5 is interrupted but the regenerative circuits are maintained. When regenerative braking ceases, the cut-out relay 61 operates to interrupt the motor circuit. A reset switch 148 is provided which, in co-operation with contacts of the master controller 1 closed only in the off position A, causes the reclosure of motor or booster overload relays 90, 91, after they have operated. The motoring and regenerative movements of the controller 2 are under the control of current limit relays 48, 45, but these relays are rendered inoperative by contacts 46, 47, while the motoring or regenerating pawls 3, 5 are effecting a controller step movement. A no-current relay 51 interrupts the motor circuit upon the occurrence of zero or lowcurrent conditions, its contacts being bridged by controller interlock contacts 18, 42 in the initial motoring position. The system is arranged for multiple-unit control and electromagnetically-operated means may replace the pneumatic drive of the controller 2.