Loss Calculations And Thermal Analysis For High Speed PM Machines

The high speed permanent magnet (PM) machine has been widely investigated since it has small size, high efficiency and power density. Distributed power generation takes pressure off electric transmission infrastructure and has benefits, such as low emissions, fuel flexibility and high efficiency.The main advantages of the high speed PM machine are small volume and great power density. However, the cooling problem is more serious due to the greater loss per volume and the smaller cooling area. In addition, the high temperature can make the permanent magnet demagnetized. So it is especially important to calculate the power loss of the machine accurately. So this dissertation aims at academic research and experimental study of high speed PM machine losses and temperature rise.Firstly, experimental study is done to test the loss coefficient of steel lamination for different frequencies and different rolling directions. The stator iron loss is analyzed and calculated. Because the frequency is high, the iron loss calculation method of traditional machine is not fit to high speed machine. A measuring approach of core loss coefficients for different frequencies is proposed. And based on the test, regression analysis is done for two kinds of iron loss calculation model. Calculation method of core loss based on finite element analysis is introduced. And the stator loss of different operated state and different stator structure is analyzed.Secondly, other losses including eddy current loss in rotor, air friction loss and copper loss are analyzed and calculated. The eddy current loss distribution in enclose and PM is analyzed, and the eddy current loss of different operate state and different stator structure is analyzed; the air friction of different rotate speed and different axial air flux is calculated; the impact of the skin effect on resistance is researched, and the copper loss is calculated.Thirdly, after calculating iron loss, eddy current loss in the rotor, air friction loss and copper loss, using them as heat source, the stationary temperature rise of the stator and rotor are calculated respectively with two dimensional finite element method. Finally, a high speed permanent magnet prototype with rated speed of 60000r/min has been tested. The temperature rise of stator and rotor, and the total loss of the machine are measured at different speed in no load condition. The total loss is separated into several parts loss using a new method. By comparing the test result to calculation result, the theoretical analysis of the high speed PM machine is partly proved to be correct.