Iso efficiency contour measurement results for variable speed drives

The efficiency of variable speed drives with induction motors and permanent magnet synchronous motors has received little attention so far in international standards. However the number of such applications is increasing rapidly and the potential energy savings are large. This paper is based on a measurement campaign of three collaborating research institutes and reports on the efficiency of motors up to 15 kW. The efficiency values are represented by means of iso efficiency contours. From these contours, the efficiency for IE1, IE2 and IE3 induction motors is compared with that of a permanent magnet machine for the entire torque - speed operation region. Also the impact of flux optimization with induction motors is analyzed. The required number of measurement points to construct accurate iso efficiency contours with minimum measurement effort is also discussed.