Design of a double-jacketed, closed type calorimeter for direct measurement of motor losses

In this paper. we report the use of a closed type calorimeter with a secondary cooling circuit of water and direct measurement of power losses. The target specification is the determination of losses up to 600 W to accuracy of 1 W or about 0.2% of full scale. A second thermally insulating enclosure is used to prevent heat loss through the calorimeter walls and enables accurate direct measurement of the power to be made without increasing the time constant of the thermal system. The calorimeter has been designed for motors up to a frame size of 90S, or about 1.1 kW, which is suited to the measurement of machines for domestic appliances. Initial results show that the calorimeter is accurate to at least 2 W with a resolution of about 0.1 W.