# 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? 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). 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). 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__________.

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

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 __________. 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 _______. 