Temperature effects on torque production and efficiency of PM motors using NdFeB magnets

Abstract

The author investigates the temperature effects of PM (permanent magnet) motors using neodymium magnets on the torque production capability and on the efficiency of the motor. When PM motors are designed to operate in a wide temperature range, the reversible demagnetization of the neodymium magnets with temperature and the increase in winding resistance with temperature influence the maximum torque capability at rated speed and efficiency of the PM motor. The maximum torque at rated speed is limited due to the fixed DC link voltage of the inverter feeding the motor. It is shown that over an operating range of -40 degrees C to 150 degrees C the maximum torque capability and efficiency of the motor can vary over a wide range. It is also shown that for certain designs a nearly flat maximum torque versus temperature characteristics may be obtained. PM motors with trapezoidal back electromotive force waveform are considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>