Speed Regulating System Providing Slowdown Control for a Motor having a Unidirectional Converter Armature Supply

摘要

1,172,415. Control of D.C. motors. WESTINGHOUSE ELECTRIC CORP. 4 April, 1967 [25 April, 1966], No. 15302/67. Heading H2J. [Also in Division G3] A D.C. motor having armature 12 and shunt field winding 14 is supplied from three-phase source 18 through converter 22. A set-point signal T is derived from circuit 38 and is compared with a negative feedback signal t, representing load tension, in controller 36 whose output signal S is applied to speed controller 26. A negative feedback signal s is derived from tachometer generator 40 and is summed with the signal S to produce signal C. A signal c represents armature current and is summed with signal C by controller 28. A circuit 44 produces a simulated current signal cRM for application to the controller 28 and summation with the signal C when forward armature current drops to zero. The output of the current controller 28 is a reference signal V for voltage controller 32 which also receives feedback signal v, and provides signal P for pulse generator 48 associated with amplifier 50 and converter 22. The field winding 14 is supplied through forward converter 56 or reverse converter 58, the signal T passing through inverter 60 to a CEMF controller 62. The latter sums the signal T with signals c and v, and its output is applied to field current controller 64 which also receives feedback through sensor 66 and function generator 68. A field voltage controller 70 receives signals from the controller 64 and sensor 72, and the resultant output signal is applied to pulse generators 74, 76, for thyristor firing angle control in the converters 56, 58. If the speed is below the setpoint, the armature voltage is increased and the forward field excitation may be reduced to clamp the CEMF at a rated maximum. Excess speed causes coasting operation, until positive braking operation is introduced by field reversal and regeneration at 5% excess speed. When the armature voltage becomes negative and exceeds a set-point voltage V1, relay 84 operates to couple inverter 92 between controllers 26, 28, the firing angle of the converter 22 being advanced. Relay 94 responds upon demand for braking to by-pass inverter 100, the relay being operated by comparator 102 receiving a set-point signal V2 and a speedresponsive signal. The field current is reversed, and the motor speed is decreased by regenerative braking until the relays 82, 94 drop out at 1 % overspeed. Final speed reduction is achieved by coasting, the armature current being shut-off and the field restored to the forward-connection.