Transient thermal analysis of a copper rotor induction motor using a lumped parameter temperature network model

Due to the advantages of higher efficiency, low manufacturing cost and lower machine weight, Copper Rotor Induction Motor (CRIM) is a suitable cost effective alternative choice over permanent magnet motor in EV/HEV traction applications [1]. However, temperature rise issue is a critical factor that has direct effects on machine parameters such as effective resistances and inductances as well as magnetic properties of the machine materials. In this paper, a lumped parameter thermal network (LPTN) model is proposed to predict transient thermal behaviour in a Totally Enclosed Fan Cooled (TEFC) CRIM considering non-existent of forced convection heat transfer in stator end-winding due to smooth rotor geometry. The model also takes into consideration of various losses as heat sources that are determined from motor loading experiments. In order to validate thermal model, a 20-hp CRIM is tested under varying speed and loading conditions to measure the actual operating temperature rise and compared with calculated temperature rise.