1
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A $$1:1$$ pulse transformer $$(PT)$$ is used to trigger the $$SCR$$ in the adjacent figure. The $$SCR$$ is rated at $$1.5$$ $$kV$$, $$250$$ $$A$$ with $${{\rm I}_L} = 250\,mA,\,\,{{\rm I}_H} = 150\,mA,$$ and $${{\rm I}_{G\max }} = 150mA$$ with $${{\rm I}_L} = 250\,mA,$$ $${{\rm I}_{G\min }} = 100mA.$$ The $$SCR$$ is connected to an inductive load, where $$L$$ $$=150$$ $$mH$$ in series with a small resistance and the supply voltage is $$200$$ $$V$$ $$dc.$$ The forward drops of all transistors/diodes and gate $$-$$ cathode junction during $$ON$$ state are $$1.0V$$

The minimum approximate volt $$-$$second rating of the pulse transformer suitable for triggering the $$SCR$$ should be: (Volt - second rating is the maximum of product of the voltage and the width of the pulse that may be applied)

A
$$2000\,\mu \,\,V - s$$
B
$$200\,\mu \,\,V - s$$
C
$$20\,\mu \,\,V - s$$
D
$$2\,\mu \,\,V - s$$
2
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A $$1:1$$ pulse transformer $$(PT)$$ is used to trigger the $$SCR$$ in the adjacent figure. The $$SCR$$ is rated at $$1.5$$ $$kV$$, $$250$$ $$A$$ with $${{\rm I}_L} = 250\,mA,\,\,{{\rm I}_H} = 150\,mA,$$ and $${{\rm I}_{G\max }} = 150mA$$ with $${{\rm I}_L} = 250\,mA,$$ $${{\rm I}_{G\min }} = 100mA.$$ The $$SCR$$ is connected to an inductive load, where $$L$$ $$=150$$ $$mH$$ in series with a small resistance and the supply voltage is $$200$$ $$V$$ $$dc.$$ The forward drops of all transistors/diodes and gate $$-$$ cathode junction during $$ON$$ state are $$1.0V$$

The resistance $$R$$ should be

GATE EE 2007 Power Electronics - Power Semiconductor Devices Question 7 English
A
$$4.7k\Omega $$
B
$$470k\Omega $$
C
$$47\Omega $$
D
$$4.7\Omega $$
3
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A single $$-$$ phase, $$230$$ $$V$$, $$50$$ $$Hz$$ $$ac$$ mains fed step down transformer $$(4:1)$$ is supplying power to a half $$-$$ wave uncontrolled $$ac$$ $$-$$ $$dc$$ converter used for charging a battery ($$12$$ $$V$$ $$dc$$) with the series current limiting resistor being $$19.04\,\Omega $$. The charging current is
A
$$3.43$$ $$A$$
B
$$1.65$$ $$A$$
C
$$1.22$$ $$A$$
D
$$1.0$$ $$A$$
4
GATE EE 2007
MCQ (Single Correct Answer)
+1
-0.3
A single phase full $$-$$ wave half $$-$$ controlled bridge converter feeds an inductive load. The two $$SCR's$$ in the converter are connected to a common $$DC$$ bus. The converter has to have a free wheeling diode
A
because the converter inherently does not provide for free - wheeling
B
because the converter does not provide for free - wheeling for high values of triggering angles
C
or else the free - wheeling action of the converter will cause shorting of the $$AC$$ triggering angles
D
or else if a gate pulse to one of the $$SCR$$s is missed, it will subsequently cause a high load current in the other $$SCR$$.
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