ABSTRACT
A thyristor can be turned on by applying a pulse of short duration. Once the thyristor is on, the gate pulse has no effect, and it remains on until its current is reduced to zero. It is a latching device. Pulse-width modulation techniques can be applied to controlled rectifiers with bidirectional switches in order to improve the input power factor of the converters. A controlled rectifier converts a fixed AC voltage to a variable DC voltage and uses thyristors as switching devices. Ideally, the output voltage of an ideal rectifier should be pure sine wave and contain no harmonics. That is, the total harmonic diction (THD) of the input current and output voltage should be zero, and the input power factor should be unity. However, the THD and power factor of a controlled rectifier will differ from the ideal values.
