Speed control for asynchronous motor in crane - has two of three phases each controlled by series triac. or thyristors in antiparallel

摘要

The speed control has two triacs (4,5) controlling two of the motor's three phases. The triacs are controlled by one of the three phases. Each triac may be replaced by two antiparallel thyristors. The motor (1) starts and stops smoothly. The control is simple and is intended especially for motors used in cranes. Two of the motor's windings are each connected via a triac to the input of a rectifier bridge (6). The bridge's dc output is connected via a resistor network to one of the windings and via a diac (7) to the gates of both triacs. The resistor network contains a variable resistor (12) for controlling the speed of the motor.