VEHICLE ELECTRIC MOTOR DRIVE SYSTEM

1298615 Automatic speed control ALLIS-CHALMERS MFG CO 6 May 1970 [13 May 1969] 21847/70 Heading G3R [Also in Division H2] A drive system provides constant output power over a speed range for a selected power output level, and, as shown, comprises a prime mover 20 on a vehicle driving high frequency polyphase alternators 30, 32 supplying synchronous traction motors 50. Each motor has a three-phase armature winding 54X, Y, Z, a solid ferromagnetic rotor 52, having chord-like portions at both ends, and a field winding 56, the armature winding being supplied from a frequency changer 58 comprising silicon controlled rectifiers associated with firing circuit 60. In order to lock the rotor and stator poles of each motor, the stator voltage is synchronized with the speed and is phaseadvanced by the angle between the flux produced by the field current acting alone and the flux corresponding to the terminal voltage. The magnitude of the stator voltage is varied as a function of the speed. For these purposes, a vector adder 64 has sine and cosine windings 68, 70 associated with a contoured rotor 74 and three-phase output windings 66 X, Y, Z for controlling the converter 58. The desired variations of terminal voltage and displacement angle with speed are expressed graphically by polar co-ordinates while the sine and cosine signals are regulated in accordance with rectangular co-ordinates. An angle sensor control 76 receives a reference power signal from circuit 78 which depends on the position of pedal 44, and independently controls the signals applied to windings 68, 70. The control 76 also receives a signal from tachometer 80 so that the voltages induced in windings 66X, Y, Z, vary linearly from zero speed up to a full value corresponding to the position of pedal 44. The three-phase high-frequency voltages from windings 66X, Y, Z, are demodulated in a discriminator 82 to remove the carrier signal, and are applied to a clipping circuit 84 associated with the firing circuit 60. The latter combines reference signals from filter 86 with signals from the circuit 84 to derive three sequence signals. The firing circuit 60 comprises level detectors for sensing the zero crossing points of the sequence signals and generate the gating signals for the controlled rectifiers of the converter 58. In order to compensate for motor voltage drop under load, control 76 increases the magnitude of the output signal from angle sensor 64 and also varies the phase angle of the output signal