1. The function of interpoles in a DC machine is
Answer : improve commutation
Explanation:-
2. A 220 V DC Shunt Motor develops a Torque of 45 N-m at an armature current of 10 A. The torque developed when the armature current 20 A is
Answer : 90 N-m
Explanation:-
Torque∝Current (DC Shunt motor)
T1=45N-m,I1=10 A
I2=20 A
T1/T2=I1/I2
45/T2=10/20
T2=(45*20)/10
T2=90 N-m
3. In a DC Shunt motor, three point starters are not suitable for applications where speed variation by flux control is required because the motor may
Answer : stop at very high speed
Explanation:-
4. Which of the following tests can be used to determine the no-load losses in a DC shunt motor
Answer : Swineburne's test
Explanation:-
5. A 150 V DC Motor of armature resistance 0.4 has backemf of 142V. The armature current is
Answer : 20 A
Explanation:- Eb=V-IaRa
Ia=(V-Eb)/Ra
Ia=8/0.4
Ta=20 A
6. In a DC Series Motor if saturation occurs at overload condition then the Torque/armature current characteristic (Ta/Ia graph) is a
Answer : Parabola up to full load and a straight line at overloads
Explanation:-
7. A circuit has a resistance of 12 and an impedance of 15 then the power factor of the circuit will be
Answer : 0.8
Explanation:- Power factor=R/Z=12/15=0.8
8. In a series RLC Circuit, capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to
Answer : L/2
Explanation:-
9. The power of a three phase three wire balanced system was measured by two watt meter method. The reading of one of the watt meters was found to zero. The power factor of the system is
Answer : 0.5
Explanation:-
10. The essential condition for operating two single phase transformers in parallel is that they should have same
Answer : Polarity
Explanation:-
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