| In this research, diagnostic and protection circuits along with various control strategies, which can be used as units in the intelligent modules for a new power device called MOS Controlled Thyristor (MCT), were designed and implemented.; A simple PSpice model which represents most of the MCT properties was derived and used in the analysis and design of power conversion circuits. A variable-frequency and variable-duty-cycle gate drive circuit was designed and implemented for the MCT to be used as a switch in a dc chopper. An improved control scheme, to operate the MCT for lagging, leading, and unity power factors in a phase-controlled rectifier and an ac-voltage controller, was developed. The scheme uses a ramp signal and a ramp-window-comparator to obtain the desired delay and extinction angles. The output from the ramp-window-comparator is passed through an RC network and a Baker's clamp push-pull which increases the current gain. The push-pull also modifies the exponential output of the RC network into pulses of small rise time. A scheme for protecting the MCT against overcurrent was also implemented. The protection circuit developed can be easily implemented in any converter circuit which uses the MCT as the power switch.; A non-linear analysis of the performance of the snubber protecting the MCT in a chopper circuit is presented. The effect of snubbers in reducing the switching loss and peak power loss and in modifying the switching trajectory in the MCT chopper were studied. Also, the effect of the snubber in reducing the electromagnetic interference was studied by measuring the radiated electric and magnetic emissions from the MCT chopper with and without the snubber.; Sinusoidal PWM (SPWM) is commonly used to eliminate lower order harmonics in a converter. However, the SPWM scheme has some inherent drawbacks when applied to a rectifier. The inverted-sine PWM (ISPWM) scheme proposed uses a high-frequency inverted-sine wave as the carrier, and it has a better spectral quality and higher average value of the output voltage. The analysis and implementation of ISPWM for MCT rectifiers are presented. |
