Simplified measuring technique for the fundamental output voltage of the PWM inverter

The variable-voltage variable-frequency (VVVF) drive of an induction motor requires careful designing of the output voltage of a voltage source inverter, especially the fundamental component of the output voltage. A simplified measuring technique for obtaining the fundamental component of the output voltage is presented. The mean value of the PWM waveform is used for the purpose. It is found that the fundamental component of the PWM waveform can be expressed by the contents of zero vectors in the space vector expression. The analysis of this space vector voltage equation makes it possible to use the mean value of the voltage as the fundamental component. Experimental results show that the indicated value of the rectifier-type voltmeter approximates the RMS-value of the fundamental component.<>