Design and Calibration of Water-Cooled Calorimeter for Induction Motors

A balanced water-cooled calorimeter is designed and implemented for electromagnetic power loss measurement of a 37 kW induction motor. The electromagnetic losses of the induction motor are measured at different loads and no-load. In order to meet the IEEE 841 Standard, the ambient temperature for the test motor must not exceed 40◦C. The efficiency for the test motor is 92%, and it is expected the upper limit for the power loss of the test motor is not higher than 3.7 kW. It is approved, the calorimeter is feasible to measure power loss up to 4 kW, while the air temperature in the chamber, near to the test object, is less than 40 ◦C. Two calibration curves, one with 2 L/min and another one with 5L/min cooling flow rate are made conducted with a balance heater for the 37 kW induction motor. The first calibration curve is assigned for the total loss up to 2.5 kW and the latter for losses ranging from 2.5 to 4 kW. Using the calibration curves, reduce the balanced calorimetric measurement by almost 6 hours. A heat-compensation method for the shaft heat-leakage is suggested and employed when the test motor is coupled with a loading machine. Experiments at no-load show the highest heat-leakage is due to the shaft heat-leakage. The uncertainty of the calorimetric measurement is 2.4% when the load torque is 201 Nm