Specific to the wide speed range and large instantaneous power of the motor for electric auto-mobile, a 110kW auto-mobile switched reluctance motor is designed. The electromagnetic torque, induce voltage are calculated and the electromagnetic performance is met the requirement of electric vehicle power. The copper loss and core loss are obtained based on finite element model. In addition, the coefficient of thermal conductivity is obtained based on physical properties of materials. At last, the 3-D temperature field model is established based on ANSYS workbench and the distribution of temperature is calculated. The results show that the motor winding temperature is running smoothly under water-cooling condition. The rotor temperature is maximum, the temperature of stator winding is slightly higher than the temperature of stator core, which conforms to the thermal design requirement of motor and lays certain foundation for the optimized analysis of such kind of motor.

A closed expression for the chemical potential of Bose gases in an external one-dimensional harmonic trap, reported recently in this journal (Mungan 2009 Chemical potential of one-dimensional simple harmonic oscillators Eur. J. Phys. 30 1131–6), is approximate and not applicable for temperatures lower than a characteristic value below which the ground state becomes occupied by a macroscopic number of particles. In this letter, the correct behaviour of the chemical potential at low temperature is addressed.