1. Lamination of the transformer core is made of
A. Cast
Iron
B. Silicon
Steel
C. Aluminum
D. Cast
Steel
Answer & Solution
Answer: B
Explanation:
Silicon steels are used for electrical transformer
cores and cores of other electrical devices for the following reasons:-
1.
Low hysteresis loss.
2.
High permeability.
3.
Virtually eliminated aging.
4.
High resistance.
2. Breather is
provided in a transformer to
A. Absorb
moisture of air during breathing
B. Provide
cold air in the transformer
C. The
filter of transformer oil
D. None
of above
Answer & Solution
Answer: A
Explanation:
The primary function of the breather is to absorb
air moisture during breathing.
3. Which
of the following losses varies with the load in the transformer?
A. Core
loss
B. Copper
loss
C. Both
core & copper loss
D. None
of the above
Answer & Solution
Answer: B
Explanation:
- Copper loss is due to the ohmic resistance of the transformer
windings.
- The copper loss for the primary winding is I12
× R1 and for secondary winding is I22
× R2.
- Where I1 and I2 are current in primary and secondary winding respectively.
- R1 and R2 are the resistances of primary and secondary winding
respectively.
- It is clear that Cu loss is proportional to the square of the
current, and current depends on the load. Hence copper loss in the
transformer varies with the load.
4. A transformer
transform
A. Current
B. Voltage
& current
C. Frequency
D. Voltage
Answer & Solution
Answer: B
Explanation:
- A transformer is a static device that is used to convert the
voltage or current to a higher (step-up) or lower (step down) level.
- The Distribution Transformer, Auto Transformer, and Tap changing
Transformer basically belong to the family of Power Transformer with
respective unique features.
- In an Instrument Transformer, voltage or current on one side of the
transformer, comparatively high (therefore not suitable for direct
measurement), is scaled down to voltage or current to levels that is
convenient for measurement with suitable instrumentation.
- The two
types of Instrument Transformers are the Current Transformer and the
Potential Transformer. Some applications may call for constant current (as
in welding) or constant voltage. Such transformers am called Constant
Current and Constant Voltage Transformers.
5. Transformer
core are laminated in order to
A. Reduce
hysteresis loss
B. Reduce
hysteresis & eddy current loss
C. Minimize
eddy current loss
D. Copper
loss
Answer & Solution
Answer: C
Explanation:
- In a transformer, the eddy current loss is proportional to the
square of the diameter of the core.
- Larger the diameter, the more the eddy current loss.
- Hence
the transformer core is laminated so that the net effective diameter of
the transformer core reduces and thus eddy current loss can be minimized.