Research On High Speed Permanent Magnet Motor And Its Control System For Molecule Pump

Molecule pump is the key equipment which can provide excellent vacuum environment. In order to ensure the quality of vacuum environment, the shaft of the molecule pump is required to rotate at high speed. In this thesis, aiming at a molecule pump used in nuclear experiment, a high speed permanent magnet motor (HSPMM) is designed to drive the molecule pump directly.Firstly, basing on the characteristics of high speed permanent magnet motor and brushless direct current motor (BLDCM), the principle of electromagnetic design is summarized. Through computing in many times, the electromagnetic scheme of the motor is put forward. In order to ensure motor operate at rated speed, the intensity of rotor is also calculated.Aiming at the calculation of iron losses, through the finite element analysis(FEA), utilized the Bertotti iron loss expression and the method of approximate core loss calculation considering only the alternating magnetic filed, the iron losses of stator is calculated when the motor is operating in rated speed. With the Halbach array magnet, the waveform of the magnetic field in stator is close to sine. The iron losses of stator are reduced 10.4%.State equation of the phase current was formulated considering two phase connection and the current commutation. The parameters of the state equation are calculated by FEA. Based on the combination of electric circuit and electromagnetic field solution, the steady state performance Halbach array BLDCM of open loop is simulated. The result shows that the sine wave BLDCM is fit for high speed operation.Rotor eddy loss is the special problem of HSPMM. In this thesis, the airgap flux density variation due to slot-opening is analyzed. Related to rotor, the rotation of the harmonics of magnetic field is also analyzed. The amplitudes of the harmonics are calculated by FEA. Based on the current sheet model, the rotations of harmonics are simulated. The rotor eddy losses in no-load condition are calculated. The rotating magnetic field caused by space harmonics and time harmonics is analyzed. The rotor eddy losses in rating load condition are also calculated.The characters of double-closed-loops velocity system are introduced. Aiming at the problem of high frequency harmonics due to the chop mode, the BUCK circuit is applied to the system. The principle of harmonics reduction is analyzed. With the MATLAB/SIMULINK software, double-closed-loops velocity system with BUCK circuit is simulated.