Asynchronous motor operation circuit - uses three phase invertor and compares nominal and actual currents

摘要

The circuit has a measurement element for load current, a reference element, a switching stage for reference and control currents comparison and for derivation of switching signals. It has further a control unit for switchable rectifiers of the inverter. Switching signals trip in a first operational zone the invertor between driving voltage and zero voltage, and in a second operational zone between zero voltage and counter voltage. Depending on the position of the reference element, second operational zone is blocked when driving is required, and first operational zone is blocked when braking is required.