Questions and answers for exam Preparation

MCQs

Total Questions : 117 | Page 3 of 12 pages

Question 21. A 1000/5 A, 50 Hz correct transformer has a secondary burden comprising a non-inductance of 2Ω. What is the ratio error, if the iron loss is 3 W and magnetizing mmf is 250 A?

4%
5.7%
3.6%
4.8%

Discuss Question

Answer: Option B. -> 5.7%
Answer: (b).5.7%

Question 22. Usually a CT has ____________

Power overload capacity than PT
The same overload capacity as a PT
A higher overload capacity than a PT
No overload capacity

Discuss Question

Answer: Option C. -> A higher overload capacity than a PT
Answer: (c).A higher overload capacity than a PT

Question 23. The observation when the secondary winding of a current transformer is open-circuited is?

The whole of the primary current produces a large value of flux in the core thereby producing a large voltage in the secondary winding
The large voltage may act as a safety hazard for the operators and many even raptures the insulation
When the large magnetizing force is taken off, it leaves a large value of residual magnetism
When the large magnetizing force is taken off, it leaves a small value of residual magnetism

Discuss Question

Answer: Option B. -> The large voltage may act as a safety hazard for the operators and many even raptures the insulation
Answer: (b).The large voltage may act as a safety hazard for the operators and many even raptures the insulation

Question 24. A (350 A/ 7A), 50 Hz current transformer has a primary bar. The secondary burden is a pure resistance of 1 Ω and it draws a current of 5 A. The magnetic core requires 350 AT for magnetization. Find the percentage ratio error.

10.56
-28.57
11.80
-11.80

Discuss Question

Answer: Option B. -> -28.57
Answer: (b).-28.57

Question 25. A 200/1 Current Transformer (CT) is wound with 400 turns on the secondary on a toroidal core. When it carries a current of 180 A on the primary, the ratio is found to be -0.5%. If the number of secondary turns is reduced by 1, the new ratio error (in %) will be?

0.0
-0.5
-1.0
-2.0

Discuss Question

Answer: Option C. -> -1.0
Answer: (c).-1.0

Question 26. The CT supplies current to the current coil of a wattmeter power factor meter, energy meter and, an ammeter. These are connected as?

All coils in parallel
All coils in series
Series-parallel connection with two in each arm
Series-parallel connection with one in each arm

Discuss Question

Answer: Option B. -> All coils in series
Answer: (b).All coils in series

Question 27. A PT is a device which is ___________

Electrostatically coupled
Electrically coupled
Electromagnetically coupled
Conductively coupled

Discuss Question

Answer: Option C. -> Electromagnetically coupled
Answer: (c).Electromagnetically coupled

Question 28. In a moving iron meter, the deflection torque is proportional to?

Square of the current through the coil
Current through the coil
Sine of measurand
The Square root of the measurand

Discuss Question

Answer: Option A. -> Square of the current through the coil
Answer: (a).Square of the current through the coil

Question 29. The full-scale deflection current of a meter is 4 mA and its internal resistance is 400Ω. This meter is to have full deflection when 400 V is measured. What is the value of the series resistor to be used?

99.90 kΩ
100 kΩ
99.60 kΩ
100 Ω

Discuss Question

Answer: Option C. -> 99.60 kΩ
Answer: (c).99.60 kΩ

Question 30. The full-scale deflection current of an ammeter is 4 mA and its internal resistance is 400Ω. If this meter is to have a full deflection of 10 A, what is the value of the shunt resistance to be used?