High Temperature, Buried Permanent Magnet, Brushless DC Motor



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A high temperature magnetic bearing system using high temperature permanent magnets from Electron Energy Corporation (EEC) is under development. The system consists of two radial bearings, one thrust bearing, two radial catcher bearings and one motor. The purpose of this research is to develop one of the critical components of the system, namely, the High Temperature Permanent Magnet motor. A novel High Temperature Permanent Magnet (HTPM) Brushless DC(BLDC) motor capable of operating at 1000 degrees F (538 degrees C) is designed. HTPMs developed at Electron Energy Corporation are buried into the rotor. The high temperature motor is designed to produce 5.1kw of power at a top running speed of 20000 rpm. The numerical values of the motor voltage, power and torque output are predicted from calculations of the nonlinear finite element model of the motor. The motor stator is wound, potted, cured and high potential tested at 1000 degrees F. A servo amplifier from Advanced Motion Control is used to drive the high temperature motor. High temperature displacement sensors are set up for sensing the rotor position to form a closed loop motion control. However, the noise problem of the high temperature sensors causes a failure of this approach. An open loop approach is then developed and this approach succeeds in spinning the rotor with the capability of self-starting. The status of the full system assembling is introduced. Some other components of the system are briefly presented.