Abstract
The need of a sustainable clean future has paved the way for environmental friendly electric vehicle technology. In electric vehicles, overloading is limited by the maximum temperature rise in the electric motor. Although an improved cooling jacket design is of vital importance in lowering the maximum temperature of the motor, there has not been as much study in the thermal analysis of motors compared to electromagnetic design studies. In this study, a three-dimensional steady state numerical method is used to investigate the performance of a cooling jacket using water as the primary coolant of a three-phase induction motor with special emphasis on the maximum temperature and the required pumping power. The effective thermal conductivity approach is employed to model the stator winding, stator yoke, rotor winding and rotor yoke. Heat transfer by induced air is treated as forced convection at the motor ends and effective conductivity is obtained for air in the stator-rotor gap. Motor power losses, i.e., copper and iron losses, are treated as heat generation sources. The effect of bearings and end windings is not considered in the current model. Pressure and temperature distributions under various coolant flow rates, number of flow passes and different cooling jacket configurations are obtained. The study is successful in identifying the hot spots and understanding the critical parameters that affect the temperature profile. The cooling jacket configuration affects the region of maximum temperature inside the motor. Increasing the number of flow passes and coolant flow rate decreases maximum motor temperature but results in an increase in the pumping power. Of the cooling jacket configurations and operating conditions investigated, a cooling jacket with six passes at a flow rate of 10 LPM with two-port configuration was found to be optimal for a 90-kW induction motor for safe operation at the maximum output.
Highlights
To realize a sustainable green future, it is imperative to reduce internal combustion engine vehicles in the transportation sector whose exhausts contribute a substantial portion in global warming and depletion of fossil fuels [1]
Simulations are performed with flow rates ranging from five to 30 LPM on four, six, eight and ten flow passes where all three-jacket inlet and outlet port configurations are employed for every case
Kral et al [17] studied thermal model of totally enclosed water-cooled induction machine for the purpose of traction applications. Their thermal analysis of an induction motor, which compared well with experimental measurements, showed that the highest temperature rise occurs in the stator windings
Summary
To realize a sustainable green future, it is imperative to reduce internal combustion engine vehicles in the transportation sector whose exhausts contribute a substantial portion in global warming and depletion of fossil fuels [1]. In the scope of EVs, the electric motor has to withstand the load exceeding its rated value for short periods of time This is limited by the maximum temperature rise allowed which can be relaxed when more heat is removed and that has led to the implementation of cooling jackets [16,17,18]. The complicated interaction of heat exchange modes in electric motors warrants the use of a 3-D numerical analysis to calculate the complete temperature field within the motor, thereby allowing us to identify the location of hot spots and to study the effects of different design and operating conditions of cooling jackets on the temperature field.
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