DC motor automatic two-zone speed control - by varying voltage at constant field excitation and vice=versa

摘要

The automatic speed control arrangement for a DC motor provides tow-zone speed control, i.e. at low speeds control is effected by varying the voltage applied to the armature while maintaining constant field excitation, and at high speeds vice versa. The arrangement includes a unipolar voltage regulator (9) receiving a reference voltage (10) and a signal proportional to the motor voltage from voltage sensor (11). An e.m.f. regulator (6) receives the output of regulator (9), a signal proportional to the motor back e.m.f. and hence motor speed from e.m.f. sensor (8), and a reference voltage (7) proportional to the rated e.m.f. of the motor. A field current regulator (4) receives the output of regulator (6) and a signal proportional to the motor field current from sensor (5). The output of regulator (4) controls a rectifier (3) providing current to the field winding of the motor.