1
GATE EE 2000
Subjective
+5
-0
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 excitation current. The motor current rises from $${I_{\min }}\,\,$$ to $${I_{\max }}\,\,$$ in the $${T_{on}}$$ period Ton of the chopper; and drops from $${I_{\max }}\,\,$$ to $${I_{\min }}\,\,$$ in the $${T_{off}}$$ period Toff of the same circuit. Both the rise and fall of the current may be assumed to be approximately linear. What is the average power loss in the machine armature?
2
GATE EE 2000
MCQ (More than One Correct Answer)
+1
-0.3
Triangular $$PWM$$ control, when applied to a $$BJT$$ based three phase voltage source inverter, introduces.
A
low order harmonic voltages on the $$dc$$ side.
B
very high order harmonic voltage on the $$dc$$ side
C
low order harmonic voltage on the $$ac$$ side
D
very high order harmonic voltage on the $$ac$$ side
3
GATE EE 2000
+2
-0.6
A three phase voltage source inverter supplies a purely inductive three phase load. Upon Fourier analysis, the output voltage waveform is found to have an $${h^{th}}$$ order harmonic of magnitude α h times that of the fundamental frequency component $$\left( {{\alpha _h} < 1} \right),$$ the load current would then have an $${h^{th}}$$ order harmonic of magnitude
A
zero
B
$${{\alpha _h}}$$ times the fundamental frequency component
C
$${h{\alpha _h}}$$ times the fundamental frequency component
D
$${\raise0.5ex\hbox{\scriptstyle {{\alpha _h}}} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{\scriptstyle h}}$$ times the fundamental frequency component
4
GATE EE 2000
Subjective
+5
-0
A single phase voltage source of magnitude $${V_s}$$ and frequency $$\omega \,\,\left( {rad\,/\,\sec } \right)$$ is connected to an inductance $$L$$ through an antiparallel back-to-back pair of thyristors. The forward and reverse conducting thyristors are fired at an angle of $$\alpha \ge \pi /2$$ from the positive going and negative going zer crossings of the supply voltage respectively, in each cycle. Obtain an expression for the inductor current in each cycle for a given value of $$\alpha .$$ The voltage drop across the thyristors, when either of them is in conduction, may be assumed to be negligible.
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