GATE EE
Power Electronics
Choppers and Commutation Techniques
Previous Years Questions

Marks 1

The steady state current flowing through the inductor of a DC-DC buck boost converter is given in the figure below. If the peak-to-peak ripple in the ...
A buck converter, as shown in Figure $$(a)$$ below, is working in steady state. The output voltage and the inductor current can be assumed to be rippl...
In the following chopper, the duty ratio of switch $$S$$ is $$0.4.$$ If the inductor and capacitor are sufficiently large to ensure continuous inducto...
A step-up chopper is used to feed a load at $$400$$ $$V$$ $$dc$$ from a $$250$$ $$V$$ $$dc$$ source. The inductor current is continuous. If the ‘off’ ...
The power electronic converter shown in the figure has a single-pole double-throw switch. The pole $$P$$ of the switch is connected alternately to thr...
A step down chopper is operated in the continuous conduction mode in steady state with a constant duty ratio $$D.$$ If $${V_0}$$ is the magnitude of t...
In a thyristor $$dc$$ chopper which type of commutation results in best performance?
Consider the chopper circuit of figure. The chopper operates at $$400$$ $$Hz$$ and $$50$$% duty cycle. The load current remains almost ripple free at...
A $$dc$$ to $$dc$$ transistor chopper supplied from a fixed voltage $$dc$$ source feeds a fixed resistive-inductive load and a free-wheeling diode. Th...
Match the following List $$-$$ $${\rm I}$$ $$A.$$ Commutation $$B.$$ $$V$$ $$-$$ Curves $$C.$$ Free wheeling diode $$D.$$ Overlap List $$-$$ $${\rm II...
A chopper operating at a fixed frequency is feeding an $$R$$-$$L$$ load. As the duty ratio of the chopper is increased from $$25\% $$ to $$75\% $$, th...

Marks 2

The figure shows two buck converters connected in parallel. The common input dc voltage for the converters has a value of 100 V. The converters have i...
A dc to dc converter shown in the figure is charging a battery bank, B2 whose voltage is constant at 150 V. B1 is another battery bank whose voltage i...
In the circuit shown all elements are ideal and the switch $$S$$ is operated at $$10$$ $$kHz$$ and $$60$$% duty ratio. The capacitor is large enough s...
The input voltage $${V_{DC}}$$ of the buck-boost converter shown below varies from $$32$$ $$V$$ to $$72$$ $$V.$$ Assume that all components are ideal,...
For the switching converter shown in the following figure, assume steady-state operation. Also assume that the components are ideal, the inductor curr...
A buck converter feeding a variable resistive load is shown in the figure. The switching frequency of the switch $$S$$ is $$100$$ $$kHz$$ and the duty...
The circuit shown is meant to supply a resistive load $${R_L}$$ from two separate $$DC$$ voltage sources. The switches $$S1$$ and $$S2$$ are controlle...
A self commutating switch $$SW,$$ operated at duty cycle $$\delta $$ is used to control the load voltage as shown in the figure Under steady state ...
Figure (i) shows the circuit diagram of a chopper. The switch $$S$$ in the circuit in figure (i) is switched such that the voltage $${V_D}$$ across th...
In the figure shown below, the chopper feeds a resistive load from a battery source. $$MOSFET$$ $$Q$$ is switched at $$250$$ $$kHz,$$ with a duty rati...
In the figure shown below, the chopper feeds a resistive load from a battery source. $$MOSFET$$ $$Q$$ is switched at $$250$$ $$kHz,$$ with a duty rati...
In the circuit shown, an ideal switch $$S$$ is operated at $$100$$ $$kHz$$ with a duty ratio of $$50%$$. Given that $$\Delta {i_c}$$ is $$1.6$$ $$A$$ ...
A voltage commutated chopper circuit, operated at $$500Hz,$$ is shown below. If the maximum value of load current is $$10A,$$ then the maximum current...
The L-C circuit shown in the figure has an inductance $$L=1mH$$ and a capacitance $$C = 10\mu F.$$ The initial current through the inductor is zero, w...
The L-C circuit shown in the figure has an inductance $$L=1mH$$ and a capacitance $$C = 10\mu F.$$ The $$L$$-$$C$$ circuit $$Q.13$$ is used to commuta...
In the chopper circuit shown, the main thyristor $$\left( {{T_M}} \right)$$ is operated at a duty ratio of $$0.8$$ which is much larger than the commu...
In the circuit shown in the figure, the switch is operated at a duty cycle of $$0.5.$$ A large capacitor current is connected across the load. The ind...
The circuit in the figure is current commutated $$dc$$ $$-$$ $$dc$$ chopper where, $$T{h_M}$$ is the main $$SCR$$ and $$T{h_AUX}$$ is the auxiliary $$...
A voltage commutated chopper operating at $$1$$ $$kHz$$ is used to control the speed of $$dc$$ motor as shown in figure. The load current is assumed t...
A voltage commutated chopper operating at $$1$$ $$kHz$$ is used to control the speed of $$dc$$ motor as shown in figure. The load current is assumed t...
A voltage commutation circuit is shown in figure. If the turn off time of the $$SCR$$$$s$$ is $$50$$ $$\mu \sec $$ and as safety margin of $$2$$ is c...
The given figure shows a step $$-$$ down chopper switched at $$1$$ $$KHz$$ with a duty ratio $$D = 0.5.$$ The peak - peak ripple in the load current i...
Figure shows a chopper. The device $${S_1}$$ is the main switching device. $${S_2}$$ is the auxiliary commutation device. $${S_1}$$ is rated for $$400...
Figure shows a chopper operating from a $$100$$ $$V$$ $$dc$$ input. The duty ratio of the main switch $$S$$ is $$0.8.$$ The load is sufficiently induc...
A chopper is employed to charge a battery as shown in figure. The charging current is $$5A$$. The duty ratio is $$0.2.$$ The chopper output voltage is...
In the chopper circuit shown in fig the input $$dc$$ voltage has a constant value $${{V_s}}$$. the output voltage $${{V_0}}$$ is assumed ripple free. ...
A step down chopper operates from a $$dc$$ voltage source $${V_s}$$ feeds a $$dc$$ motor armature with a back $$e.m.f$$ $$\,\,{E_b}.$$ From oscillosco...

Marks 5

In fig, the ideal switch $$S$$ is switched on and off with a switching frequency $$f = 10 kHz.$$ The switching time period is $$\,T = {t_{ON}} + t{}_{...
A voltage commutated thyristor chopper circuit is shown in fig. The chopper is operated at $$500$$ $$Hz$$ with $$50\% $$ duty ratio. The load takes a ...
A $$dc$$ motor with armature resistance $${R_a}$$ is fed from a step down chopper in the continuous mode, and operates at some known speed and known e...
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