# GATE Questions & Answers of Line Commutated Thyristor Based Converters

## What is the Weightage of Line Commutated Thyristor Based Converters in GATE Exam?

Total 7 Questions have been asked from Line Commutated Thyristor Based Converters topic of Power Electronics subject in previous GATE papers. Average marks 1.57.

A single phase fully controlled rectifier is supplying a load with an anti-parallel diode as shown in the figure. All switches and diodes are ideal. Which one of the following is true for instantaneous load voltage and current? ##### Show Answer

The waveform of the current drawn by a semi-converter from a sinusoidal AC voltage source is shown in the figure. If $I_0=20\;A$, the rms value of fundamental component of the current is ___________A (up to 2 decimal places). ##### Show Answer

A phase controlled single phase rectifier, supplied by an AC source, feeds power to an R-L-E load as shown in the figure. The rectifier output voltage has an average value given by $V_\circ=\frac{V_m}{2\mathrm\pi}(3+\cos\;\alpha)$, where $V_m=80\mathrm\pi$ volts and $\mathrm\alpha$ is the firing angle. If the power delivered to the lossless battery is 1600 W, $\mathrm\alpha$ in degree is________ (up to 2 decimal places). ##### Show Answer

The figure below shows the circuit diagram of a controlled rectifier supplied from a 230 V, 50 Hz, 1-phase voltage source and a 10:1 ideal transformer. Assume that all devices are ideal. The firing angles of the tyristors T1 and T2 are 90° and 270°, respectively. The RMS value of the current through diode D3 in amperes is__________.

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A single-phase thyristor-bridge rectifier is fed from a 230 V, 50 Hz, single-phase AC mains. If it is delivering a constant DC current of 10 A, at firing angle of 30o, then value of the power factor at AC mains is

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A full-bridge converter supplying an RLE load is shown in figure. The firing angle of the bridge converter is 120º. The supply voltage   . The inductor L is large enough to make the output current IL a smooth dc current. Switches are lossless. The real power fed back to the source, in kW, is __________. ##### Show Answer

In the given rectifier, the delay angle of the thyristor ${\mathrm{T}}_{1}$ measured from the positive going zero crossing of ${\mathrm{V}}_{\mathrm{s}}$ is 30°. If the input voltage ${\mathrm{V}}_{\mathrm{s}}$ is $100\;\sin\left(100\prod\mathrm t\right)\mathrm V$, the average voltage across R (in Volt) under steady-state is _______. 