Speed regulation and control system for DC motor - uses back-EMF measured during regularly imposed supply interruptions as control quantity, comparing it with reference value.

摘要

The motor supply is interrupted every 10ms for 1ms, during which time(Tc) speed declines only slowly. Open-circuit motor voltage, after initial fluctuation(Td-0.7ms), settles to a decremental curve(Te-0.3ms). Measurements of this speed-related back-EMF are compared with a reference value representing the desired speed. The error signal is used to correct variations from the set speed. A sequencer ensures measurements are made at the correct times. Opt., the interrupted supply voltage is obtained, without switching, from a full-wave rectified 50 Hz mains supply, unfiltered, followed by a peak-lopping zener diode. Several variants are described. Overload protection can also be obtained by voltage measurements at either end of the decremental period(Te). USE/ADVANTAGE - Simple control without speed sensors or series resistors for motors under 1kW.