Double chamber calorimeter (DCC): a new approach to measure induction motor harmonic losses

Abstract

Direct measurement of electric machine losses using the principle of the calorimetric method is described in this paper. The design and construction of a double chamber calorimeter (DCC) that can be used for measurement of harmonic losses of a 7.5 kW cage induction motor is discussed. The advantages of this approach are highlighted as compared with a single chamber type calorimeter. Conducted heat leakage through the calorimeter walls is estimated accurately by developing a simple thermal model and compared with the experimental results. Accuracy and reliability is investigated by performing experimental tests using a known heater. Limits for the air flow rate and temperature rise inside and across calorimeter chambers are derived, The calorimeter is capable of measuring a heat loss up to 1 kW corresponding to the 7.5 kW machine with an overall accuracy of /spl plusmn/15 W. This provides a high resolution required for measurement of motor harmonic losses caused by distorted waveforms.