Speed changeover circuit for three=phase motor - has triac switches in and between supply lines to motor to change mode

摘要

A current supply unit (20) is connected to the three-phase motor by a lead for each phase. In and between these lines are incorporated time switches (31-37) enabling at least two operational modes. In the first mode the leads (21-23) of the supply are permanently connected to the terminals (14-16) of the motor. In the second mode the phase voltage of one lead (22) of the supply is changed over periodically on the terminals (14-16) of the dc motor such that, with a motor with a neutral (MP), the two other leads (21, 23) of the supply are disconnected.