1. In the hopkinson’s test on two DC machines. Machine A has field current of 1.4A and B has field current of 1.3A. Which machine acts as motor?
a) B
b) A
c) A, B
d) None of the mentioned
Explanation: Ea/Eb = 1.4/1.3
Ea = 1.077 Eb > Eb
So, the machine will act as motor.
2. In the Hopkinson’s test on two DC machines. Machine A has field current of 1.4A and B has field current of 1.3A. Which machine acts as generator?
a) B
b) A
c) A,B
d) None of the mentioned
Explanation: Ea/Eb = 1.4/1.3
Ea = 1.077 Eb > Eb
So, the machine will act as generator.
3. Hopkinson’s test is also called regenerative test due to ____________
a) energy of one machine is used to drive other
b) feedback
c) losses are least
d) extra motor is used
Explanation: Regenerative phenomena utilizes the energy of the running machine to tap the dynamically produced energy and use it to charge the battery.
4. Which is the most appropriate relation to find efficiency of the generator?
a) output/(output + losses)
b) (output – losses)/input
c) (output – losses)/(output + losses)
d) any of the mentioned
Explanation: For a generator the output can be measured and so this expression is used
5. The efficiency in the swineburne’s test can be found.
a) True
b) False
Explanation: Because the constant losses are known.
6. The possible assumption is/are made while doing swineburne’s test.
(i) mechanical loss constant
(ii) Armature reaction neglected
(iii) Increases in flux
a) (i) and (ii)
b) (iii) and (i)
c) (i), (ii), and (iii)
d) (i)
Explanation:There is decrease in flux due to positive temperature coefficient of resistance in shunt machine.
7. Swineburne’s test is applicable to those machines in which flux is practically _______
a) constant
b) linear
c) non-linear
d) none of the mentioned
Explanation: Because the constant losses are known in advance of the test is conducted.
8. Similarity between Hopkinonson’s and field’s test is that _______
a) both need similar mechanically coupled motor
b) both need similar electrically coupled motor
c) regenerative power
d) negligible power
Explanation: The machines have to be mechanically coupled together.
9.Which of the following characteristics reveal about the magnetization nature of the machine?
a) No-load characteristics
b) Load characteristics
c) Armature characteristics
d) Both no-load and load characteristics
Explanation: Both no-load and load characteristics are required to predict the magnetization of the machine.
10. Choose the most inappropriate out of the following for the no-load characteristics of the dc generator.
a) It is the open circuit characteristic of the machine
b) It is magnetization characteristic of the machine
c) It is conducted on the unloaded machine
d) None of the mentioned
Explanation: All the mentioned nature of the characteristics are correct.