1
GATE EE 1997
Subjective
+5
-0
The field coil of a two-pole $$d.c.$$ series motor is made up of two identical sections In one case
$$(i)$$ of two sections of the field coil are connected in series, and in another case
$$(ii)$$ the two sections are connected in parallel. If the motor takes the rated current in both the cases, then ratio of torque $$(1):$$ torque $$(2)$$ and speed $$(1):$$ speed $$(2)$$ respectively are
2
GATE EE 1997
Subjective
+5
-0
At $$50\% $$ of full load, the armature current drawn by a $$d.c.$$ shunt motor is $$40$$ A when connected to a $$200$$ $$V$$ $$d.c.$$ mains. By decreasing the field flux, its speed is raised by $$20\% $$ this also causes a $$10\% $$ increase in load torque. Calculate the percentage change in field current. The armature resistance including the brushes is $$1$$ $$Ohm.$$ Neglect saturation and armature reaction.
3
GATE EE 1997
MCQ (Single Correct Answer)
+1
-0.3
The low voltage winding of a $$400/230V,$$ $$1$$-phase, $$50$$ $$Hz$$ transformer is to be connected to a $$25$$ $$Hz,$$ the supply voltage should be
A
$$230$$ $$V$$
B
$$460$$ $$V$$
C
$$115$$ $$V$$
D
$$65$$ $$V$$
4
GATE EE 1997
MCQ (Single Correct Answer)
+2
-0.6
A voltage $$V=400$$ sin $$314.16t$$ is applied to a $$1$$-phase transformer on no-load. If the no load current of the transformer is $$2\sin \left( {314.16t - {{85}^0}} \right),\,\,$$ then magnetization branch impedance will be approximately
A
$$141\,\,\angle 90$$
B
$$200\,\,\angle - 85$$
C
$$200\,\,\angle 85$$
D
$$282\,\,\angle - 80$$
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