Abstract: The three-level pulse width modulation(PWM)type digital power amplifier of the active magnetic bearing based on digital signal processor(DSP)and filed programmable gate array(FPGA)is developed. The DSP chip is used to replace the analog circuit to carry out proportion-integration regulation, generate triangle carrier and generate PWM wave which is the driving signal of the load winding. Through the internal program of DSP, on-line adjustment of PWM duty cycle is realized and the line of current in the load winding of active magnetic bearing is controlled in real time, thus controlling the rotor to stably suspend in the balance position. The method of using FPGA to carry out 180°phase shift of the driving signal, i.e. PWM wave, is given, thus realizing three-level digital power amplifier. This amplifier is used in the 5-DOF active magnetic bearing test bed, so that the rotor suspends statically and stably while its peak value of vibration is less than 5μm. The approach of digital design can optimize the performance of the power amplifier, moreover it will have advantages such as small volume, strong program portability and high reliability.

Key words: Active magnetic bearing, Digital Power amplifier, Digital signal processor, Pulse width modulation