Experimental Investigation of the Losses and Efficiency of 75 kW Induction Motor Drive System

The frequency converter driven IM can be used as a reference for the efficiency level of a drive system. In here, the losses and efficiency of a 75 kW IE3 -rated modern squirrel-cage induction motor are investigated experimentally. First, the result of IEC loss segregation with sinusoidal supply is used to create a reference point. Secondly, five different commercially available voltage source converters are used to drive the same motor in 30 measurement points up to the rated speed and torque. The losses and efficiencies are analyzed with torque values of 10%, 25%, 50%, 75% and 100% of the rated torque of the motor and supply frequency values of 10%, 25%, 50%, 75%, 90% and 100% of the rated motor frequency. The results are presented as frequency - torque maps and the loss values are given as Table values. Three of these converters show very similar performance from the energy efficiency point of view. The input-output method is used to determine the losses of the motor and converter.

I. Introduction

There is an urgent need to gather information and to identify the losses and efficiencies of the electric drive equipment to understand the energy saving potential of the devices. Calculations using theoretical equations and component parameters are commonly used in the loss and efficiency determination of the converters. The most important practical methods are the method based on input and output power measurement, and the calorimetric method. In case of rotating electrical machines, finite element analysis and indirect efficiency determination are used in addition to those used for converters.