Influence of voltage and current source inverters on low power induction motors

Currently low- and medium-power induction motor drives used in industrial applications are based on voltage source inverters often with open-loop V/Hz control. The introduction of current source inverters into this area could lead to considerable marketing advantages. A comparison of the performances of a voltage-controlled current source inverter and a voltage source inverter, both feeding a low-power induction motor is presented with the aim of evaluating the potential benefits of using a current source inverter in a low-power induction motors. The experiments are designed to highlight harmonic losses, insulation stress, and common-mode phenomena. The losses in the induction motor as well as in both inverters are measured under several steady-state operating conditions. The voltage stress generated when the motor windings are switched on has been recorded for both drives. The common-mode voltage and current are also quantified and an analysis of the shaft voltage is presented. The experimental results show that the current source drive achieves a better performance in terms of the motor efficiency, insulation stress, common-mode voltage and shaft voltage.