F.P.H. Tjin A Ton Control of Three Phase Brushless DC Motors

Brushless DC motors (BLDCMs) have taken over the market for small electrical motors in consumer electronics, robotics and computer disc drives. Improvements in permanent magnets and electronics will contribute to the further increasing popularity of this motor. In BLDCMs the classical mechanical commutator is replaced by electronic components. The motor consists of a rotor containing permanent magnets and a stator with wound coils, connected in series called phases. A switching device, known as the inverter, converts the DC feeding voltage into an alternating voltage which is fed into the phases. Torque production can be seen as the interaction of the stator phase currents and the phase voltages induced by the rotor magnets. However, due to deviations from the ideal shapes of these currents and voltages, severe torque ripples can occur, being a major disadvantage of the BLDCM. This literature survey reviews the inner loop (inverter) control algorithms with special emphasis on the influence of these algorithms on the torque ripple. Voltage control is the most simple control, though torque ripple can be considerable. Current control, requiring current sensing and a more complex configuration, can reduce torque ripple, especially at lower speeds. Modified current control algorithms, matching current shape with the back-emf, can lead to very smooth torque with opportunities of accounting for production errors

Systems and Control Group

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