Thermal Analysis and Cooling System Design of Dual Mechanical Port Machine for Wind Power Application

Dual mechanical port (DMP) machine, a kind of electrical continuous variable transmission, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox in wind power application and hybrid electrical vehicles. As the inner wound rotor is surrounded by the stator and the permanent magnet (PM) outer rotor, the DMP machine suffers from possible PM demagnetization and insulation failure under severe thermal condition. In this paper, thermal analysis and cooling system design of a DMP prototype machine are investigated. To predict the heat sources in actual operation, a transient cosimulation method is presented. Thermal parameters and the flow distribution in the cooling ducts are calculated in detail. Finite-element analysis of the thermal field is carried out to obtain the temperature distribution and two typical thermal contacts are considered. A robust fully forced-air cooling system with inner rotor teeth ducts is proposed for the DMP machine and a 10-kW DMP machine is prototyped. Experimental results at different working conditions are given to verify the theoretical analysis. Both simulation and experimental results reveal that the numerical approach and the proposed cooling system are not only more accurate and reliable, but can be referred to other electrical machine cooling system design.