electrical drehzahlregelungseinrichtung for ac asynchronous motor

摘要

1,251,162. Control of A.C. motors. LANDIS & GYR A.G. 8 June, 1970 [13 June, 1969], No. 27640/70. Heading H2J. [Also in Division G3] A capacitor 16 is charged by half-wave pulses derived from a resistor 13 which is vectorially related with the field winding of an asynchronous motor 10, the voltage developed across the capacitor being inversely dependentupon the speed of the motor. When the speed exceeds a predetermined value, thyristor 14 is blocked so that the motor is supplied through a diode 15 only until the speed is restored to the desired value which may be selected by adjusting resistors 18 or 19. The resistor 13 may be replaced by a Zener diode, and a resistor having a negative temperature coefficient may be used instead of the resistor 19, Fig. 3 (not shown). The speed of the motor then decreases with rising temperature. The motor may drive a blower for the transmission of heat in a regenerative furnace to maintain a constant temperature in the space surrounding the N.T.C. resistor. In another arrangement, the discharge path for the capacitor 16 comprises a transistor amplifier for increasing the sensitivity of the temperature-dependent regulation of the speed, Fig. 4 (not shown). The diode 15 may be replaced by a thyristor which is switched on and off by external signals, Fig. 5 (not shown).