STARTING DEVICE FOR ASYNCHRONOUS MOTORS

摘要

The invention relates to a starting device for asynchronous motors, destined to step-starting of the asynchronous motors with wound rotor. The device is used in the electrical drives, operating without speed adjustment in case of a subsynchronous cascade-type configuration made with static converters. According to the invention, the device comprises a non-controlled rectifier (1) for rectifying the voltage corresponding to the three phases of a rotor of an asynchronous motor, the rectified voltage being applied to a resistor (2) divided into corresponding resistance steps which are gradually short-circuited until reaching the nominal speed, by means of a block of tyristors (3) having a number of tyristors equal to the number of resistance steps, and which are brought in the conduction state by the voltages supplied by a pulse generator (4), thereby ensuring the natural switching off of the tyristors of the block of tyristors (3) when the next tyristor enters in conduction, the switching off of the last tyristor of the block of tyristors (3) being made by cancelling the rectified current during the transitory process of establishing the nominal speed.