Recent developments in solid state ac drives have put a new emphasis on the use of the ac motor as a high performance variable speed machine. The pulse width modulated (PWM) inverter is an extremely effective motor controller accomplishing voltage and frequency adjustment in a single circuit.
In order to obtain the lowest possible harmonic contents in the inverter, the unipolar triangular modulation method has been adopted.
In this paper, timing wave is always synchronized with the reference sine wave in time phase. Since the circuit employing the uniplar triangular modulation is composed of almost digital components, it has low sensitivity to external influence.
In addition, the position control of induction motor has been described. The dynamic performance of the induction motor has been improved by employing the slip control.
