Operation of invertor-fed induction motor driving braked hoist

摘要

The operation process involves three timers (T1-T3), the first (T1) of which supplies a clock signal at /=4.5 kHz to a programmable logic circuit. A negative-going edge triggers the second timer (T2) to produce a 1-second pulse corresponding to the remagnetisation time of the invertor. Another negative-going edge triggers the third timer (T2) to produce a 130ms pulse whose width must not exceed the release time of the external motor brake. The counter-torque produced by the motor is regulated by set-point comparison in an operational amplifier.