Three-phase soft-switching PWM inverter for brushless DC motor

The brushless direct current motor (BLDCM) has high torque, compact size, and high efficiency. Therefore, BLDCM is widely used in computers, household and industrial products, and automobiles. It is usually driven by a hard-switching pulse width modulation (PWM) inverter, which has low switching frequency, high switching loss, high electro-magnetic interference (EMI) and acoustic noise, etc. To solve the drawbacks of the voltage source-type hard switching inverter, a novel zero voltage transition (ZVT) three-phase soft-switching voltage source inverter (VSI) is proposed for BLDCM drive systems. The proposed ZVT-VSI consists of three switches, six diodes, three capacitors and an inductor. Soft switching operation of all switching devices in inverter is realized by adding auxiliary resonant unit to DC link of conventional one. Auxiliary switches are also operated under zero current switching (ZCS) or zero voltage switching (ZVS). The proposed inverter is suitable for PWM operation. The soft-switching operation of the ZVT-VSI is explained in terms of modes. The validity of the topology is verified by experimental results.