Electric Motor Drive with Inverter Output Filter

The paper focuses on some aspects of control and estimation in electric drives with inverter output filters. The filters are used in some industrial drives with pulse width modulated (PWM) inverters. They smoothes the motor supply voltage and current so nearly sinusoidal shapes are obtained. The filters can also limit the bearing current and shaft voltages. Because of the voltage drop and phase shift, the motor voltages and currents differ from the inverter output. This fact can seriously complicate the drive operation due to the problems with the control and estimation process – especially in speed sensorless drives. To solve those problems the filter model should be taken into account in the control and estimation algorithms. In this paper a sensorless solution for induction motor (IM) drives is proposed together with inverter output filter. A short description and discussion of the schemes is given. Simulation and experimental results validate the proposed solution.