Arrangement for controlling the speed and rotary direction of a three-phase asynchronous motor

摘要

The invention relates to a DC control circuit for controlling the speed and rotary direction of a three-phase asynchronous motor. The circuit has an inverter section having three branches with a pair of switch elements in series in each of the branches. The inverter section has a common extinguishing switch element in shunt with the three branches. A speed determining frequency generator is responsive to the voltage of the DC supply and an ignition signal generator for operating the inverter switch elements is driven by the frequency generator. An extinction signal generator for operating the common extinguishing switch element is also driven by the frequency generator. A reversing circuit section between the ignition signal generator and the inverter branches has two states for exchanging the control lines of the inverter switch elements in at least two of the branches. A latching unit for selecting either of the two reversing states is connected to and subservient to the frequency generator to prevent initiations of reversals prior to the operation of the extinguishing switch element during each cycle of operation.