Field programmable device is used to implement a multilevel direct pulse width modulation (PWM) pulse generator for medium voltage inverters for variable speed drives such for fans and pumps. The pulse generator commutes with main controller through data bus

receives the sampling data of reference voltage

returns the operation information of power units

and outputs the PWM pulse with a modularization design. The basic principles and the hardware/software configuration of the pulse generator are described. The test waveforms of line-to-ground voltage and Fourier analyses are given. The test results demonstrate the accuracy and reliability of the pulse generator and the better output voltage with a total harmonic distortion of less than 3%.