This paper introduces a 3 phase GTO PWM inverter that supplies a variable voltage with variable frequency to control the speed of induction machines, with novel circuits for obtaining the 3 phase PWM control signals and for driving the GTOs. The control circuit generates three phase sine waves and a triangular wave with high degree of accuracy and in perfect synchronization using digital techniques. The drive circuit is a simple isolated drive circuit that receives the output of the control circuit and produces continuous uniform switching pulses with appropriate specifications for switching the GTOs from the non-conduction to the conduction state and vice-versa. The paper gives the experimental results of testing the inverter to control the speed of an I. M. |
