Laboratory Report: Background Theory

1.1 Background Information

Controlled DC rectifiers use thyristors instead of diodes to implement rectification. The operating characteristics of thyristors differ from diodes in one fundamental way – instead of automatically forward biasing when a positive voltage is applied they require both a positive voltage and a gate pulse to trigger the thyristor [1]. This has the added advantage of allowing the average DC voltage to be controlled by increasing or decreasing the firing angle of the thyristors [2]. While the turn on of the thyristors can be controlled via a gate pulse they cannot be turned off using a gate pulse, unless a commutation circuit is used [3].


[1] University of the West Indies, St. Augustine, Single Phase Full Wave Rectifiers [Online] Available: http://www.eng.uwi.tt/depts/elec/staff/rdefour/ee33d/s3_fwrc2.html

[2] N. Mohan, T.M. Undeland and W.P. Robbins, Power Electronics, Hoboken, NJ: John Wiley & Sons, Inc,2003, pp. 121-122.

[3] F. Shania, Controlled DC Rectifiers, Perth, WA: Curtin University, pp. 10-12.

*Note* The above references use IEEE formatting – check your unit outline for your referencing style.