A controlled rectifier is an electronic device that converts alternating current (AC) to direct current (DC) using semiconductor switches such as thyristors or transistors. It allows for controlling the output voltage and current, making it useful in various applications such as motor speed control and power supply regulation.
The main difference between half-wave and full-wave controlled rectifiers is the number of pulses in the output waveform. Half-wave rectifiers only use one pulse from the AC input, resulting in a pulsating DC output, while full-wave rectifiers use both positive and negative halves of the AC input, resulting in a smoother DC output.
The output voltage of a controlled rectifier is determined by the firing angle of the semiconductor switches, the peak value of the AC input voltage, and the transformer turns ratio. The formula for calculating the output voltage is VDC = Vpeak * cos(α) * N2/N1, where VDC is the DC output voltage, Vpeak is the peak value of the AC input voltage, α is the firing angle, and N2/N1 is the transformer turns ratio.
A snubber circuit is used in controlled rectifiers to reduce voltage spikes and ringing caused by the switching of the semiconductor switches. It consists of a resistor and capacitor connected in parallel and placed across the switches to absorb the excess energy and protect them from damage.
The average output voltage of a controlled rectifier can be calculated by multiplying the peak value of the output voltage by the duty cycle, which is given by (π - α)/π for half-wave rectifiers and 2(π - α)/π for full-wave rectifiers. The average output current can be calculated by dividing the output voltage by the load resistance.
