| Summary: | 碩士 === 大同大學 === 電機工程研究所 === 88 === Brushless DC motor is driven by DC voltage and is commutated electronically. The existence of winding reactance will cause current lagging with respect to the specified magnetic pole position at different velocities. Therefore, the torque developed will be reduced.
In this thesis, an improved commutation method is proposed to advance the switching time of the applied voltage. A microcontroller and additional circuitry are used to calculate the required advanced angle instantly, therefore the relative position between armature current versus magnetic pole will remain the same in a wide range of the running speeds.
In order to drive the brushless DC motor over it''s based speed, that is operated at flux-weakening region, a DC-DC boost-converter is used. Operating the boost circuit appropriately, the rotor will be speeded up and the efficient flux-linkage will be decreased to enhance the motor work in constant power region. Otherwise, control technique of regenerative braking and energy-recovery with this bidirectional boost converter is also addressed.
Finally, a hardware scheme consists of microprocessor 8XC196MC and suitable peripheral circuits, and a flexible software controlled algorithm are established for experimentation, the results prove that the proposed system can be fulfilled the requirements.
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