Important Terms - Phase Controlled Converters

Glossary

1.  Rectification:

The conversion of ac to dc is known as rectification.

2.  Semi-converters:

It combines the features of both controlled rectifiers (using SCR) and uncontrolled rectifiers (using diodes). The polarity of output voltage can be either positive ornegative.

3.  Commutation:

It is the process of turning-off of a power semiconductor device.

4.  Freewheeling diode:

A power diode connected parallel across the load to prevent the reversal of load voltage in order to improve the input power factor.

5.  Ripple:

AC component present in the DC output voltage.

6.  Delay angle:

It is defined as the angle between the zero crossing of the input voltage and the instant the thyristors is fired.

7.  Overlap period:

The period during which both the incoming and outgoing thyristors conducts simultaneously is called overlap period.

8.  Overlap angle/ commutation angle:

The angle for which both devices share conduction is known as overlap angle.

9.  Input Displacement Angle:

It is the angular displacement between the fundamental component current to the line to neutral voltage of the input ac source.

10. Displacement factor:

It is defined as the cosine of the input displacement angle.

11. Distortion factor:

It is defined as the ratio of RMS amplitude of the fundamental component to the total RMS amplitude.

12. Harmonic Factor:

It is defined as the ratio of the total harmonic content to the fundamental component.