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A rectifier is a device that is used to convert alternate current to direct current. A rectifier contains one or more diodes that acts like a one way controller that enables the electric current to move in only one direction. The process of making the current to flow in only one direction is called rectification. There is different type of rectifiers available such as vacuum tube diodes, solid state diodes, silicon controlled rectifiers, mercury arc valves and various other silicon rectifiers.
However, a diode rectifier can only convert AC to DC. It cannot regulate the output voltage. On the other hand, phase controlled rectifiers or PCRs can control the output voltage. A phase controlled rectifier is made by switching the diodes with Thyristors. The output voltage of the rectifier can be controlled by changing the firing angle of the Thyristors. One of the major applications of phase controlled rectifiers is in speed control of a DC motor.
Phase Controlled Rectifier
Phase controlled rectifier is a type of rectifier circuit which is made by switching the diodes with Thyristors or Silicon Controlled Rectifiers. The main reason of using Thyristors instead of diodes is that, Thyristors can be used to regulate the output voltage by changing the firing angle. There are different types of phase controlled rectifiers which are mentioned below:
Single Phase Rectifier
Single phase Uncontrolled Rectifier
Single Phase Half Wave Uncontrolled Rectifier
Single Phase Full Wave Uncontrolled Rectifier
Split Supply
Bridge
Single Phase Half Controlled Rectifier
Single Phase Fully Controlled Rectifier
Three Phase Rectifier
Three Phase Uncontrolled Rectifier
Three phase half wave uncontrolled rectifier
Three Phase full bridge uncontrolled rectifier
3 phase half wave controlled rectifier
Three phase fully controlled rectifier
Three phase half waver fully controlled rectifier
Three phase full bridge fully controlled rectifier
3 Phase Half Wave Controlled Rectifier
A 3 phase half wave controlled rectifier is a type of rectifier which is used with three phase alternate current input power supply. There are three types of 3 phase half wave controlled rectifier as mentioned below:
1. Semi Converter: It is a 1 quadrant converter that contains only one polarity of output current and voltage.
2. Full Converter: It is a 2 quadrants converter that contains polarity of output voltage which can be either positive or negative but only one polarity for current that is either positive or negative.
3. Dual Converter: A dual converter is a four quadrants converter that can have both polarities for output voltage and output current.
Working of 3 phase half wave controlled rectifier
A 3 phase half wave controlled rectifier is used to convert alternate current to direct current. The input alternate current is supplied from a transformer in required voltage to the Thyristor converter according to the required output direct current voltage. During the positive half cycle of the input supply the Thyristor is in forward biased state, while the upper end of the transformer is at positive potential w.r.t to the lower end. By applying suitable gate trigger pulse to the terminal of thyristors, thyristors can be activated at a delay angle.
Applications of 3 Phase Half Wave Controlled Rectifier
3 phase half wave controlled rectifiers are mostly used in paper mills, textile mills and steel mills which uses DC motor drives. Following are few of the applications of 3 phase controlled rectifier:
1. Eletro-metallurgical and electrochemical process
2. Reactor controls
3. Magnet power supplies
4. Flexible speed industrial drives.
Advantages of 3 phase half wave controlled rectifier
1. High cost filtering is not required to give a steady direct current output because ripple factor is less.
2. Rectification effectiveness and transformer utilization factor is high.
3. When compared to single phase rectifier the output current contain very less alternate current component.