Analysis of current ripple and implementation of pulse width modulation switching power amplifiers for active magnetic bearing

A three-level pulse width modulation (PWM) switching power amplifier for active magnetic bearing applications is implemented in the paper. Different from conventional two-level PWM switching power amplifier, the switching power amplifier can achieve current ripple reduction. Then an analytical method for computing the current ripple is presented. The current ripple amplitude of the three-level PWM switching power amplifier is compared with that of the two-level PWM switching power amplifier. Comparative results indicate that the three-level PWM techniques can effectively reduce the current ripple in theory. The method of control has the advantages of conventional two-level method with good output wave and fast dynamic response and it is simple to be implemented. By using a practical switching power amplifier as an illustrative example, which works in two different PWM techniques, numerical simulation and experimental method are implemented. The consistency of the final simulation results with the experimental results further indicates the feasibility and effectiveness of the used control strategy.