Techniques for efficiency improvement in PWM motor drives

In this paper a comprehensive efficiency analysis on an inverter-fed induction motor drive is proposed. The drive under study integrates both switching losses minimization by D-PWM (Discontinuous Pulse Width Modulation) for the voltage source inverter and an original version of an ELMT (Electric Loss Minimization Technique) for the motor. The two techniques are implemented, either separately or contemporary in a unique control platform in order to allow the contribution of both the chosen PWM and ELMT strategies on the power total losses to be assessed and benchmarked. Results have been compared with those achieved by the use of the classic space-vector PWM in constant rated flux operation; from this comparison the improvement of the efficiency of the whole electrical drive with the proposed techniques is demonstrated. A complete dynamic model of the drive system has been developed, which permits the drive behaviour in terms of efficiency/power losses to be evaluated in numerical simulation, properly separating each loss term. Such a complete dynamic model has been validated. Experimental results are given as well.