Derivation of motor line-current waveforms from the DC-link current of an inverter

A technique for reconstructing squirrel cage motor line currents using information from a single current transducer in the DC-link of an inverter is presented. All the instantaneous motor line currents can be reconstructed with a bandwidth limited to half the inverter switching frequency. These waveforms are used to produce a high-bandwidth signal, proportional to the scalar magnitude of the line current, and which is suitable for motor control purposes. A simple, low-cost implementation of the scheme demonstrates accurate results in a practical motor drive