EEE Bangla Interview Tips
10. When a 400Hz transformer is operated at 50 Hz, its KVA ratings is–
B. reduced 1/8
C. Increased by 8 times
D. None of above.
Generally, KVA ∝ frequency
(KVA50/KVA400) = (f50/f400) = 50/400 = 1/8
KVA50 = KVA400/8
9. The main purpose of performing open circuit test in a transformer is to measure its–
A. core loss
B. copper loss
C. insulation resistance
D. total loss
The purpose of the open-circuit test is to determine the no-load current and losses of the transformer. This test is performed on the primary winding of the transformer.
When a 6 V battery is connected across the primary of a transformer with a turns ratio of 8, the secondary voltage is
8. When a 6 V battery is connected across the primary of a transformer with a turns ratio of 8, the secondary voltage is
Battery Voltage is DC Voltage.
Transformer does not work on DC
Direct current have a constant magnetic field induced if DC Voltage supply to the primary winding of transformer. So, only a constant magnetic field will act 0V secondary.
7. The copper loss of a transformer at full load is 40W. What would be at half load-
The copper loss in transformer is equal to the I2R loss.
The copper loss in transformer gets increased with load.
The copper loss value is not constant, and it varies as the load on the transformer is increased. That is why the copper loss is also called a variable loss.
The copper loss at different loading can be calculated by this formula: Pcu=( % Load/100)2 x P
What kVA rating is required for a transformer that must handle a maximum load current of 8A with a secondary voltage of 2 kV?
6. What kVA rating is required for a transformer that must handle a maximum load current of 8A with a secondary voltage of 2 kV?
VA Rating = VxI, Active Power= VxIxp.f
For a transformer,
Vp/Vs = Np/Ns = Is/Ip
Thus the required rating = VsIs =(2kV)(8A)=16kVA
5. The leakage flux in a transformer depends upon
A. the load current.
B. the frequency.
C. the mutual flux.
D. the applied voltage.
The leakage flux in a transformer depends upon load current.
4.Breather is provided in a transformer to
A. Absorb moisture of air during breathing.
B. filter of transformer oil
C. provide cold air in transformer
D. None of above
Breather is used in a transformer to filter out the moisture from the air.
Breather consists of silica gel which absorbs moisture from the air.
The Color of good/new silica gel is blue. The moist silica gel became pink in color
3. Transformer is used for—
A. to step down voltage
B. to step up and step down primary voltage
C. to step up voltage
D. None of above
A transformer is often used to reduce the voltage level of conventional power circuits to operate low-voltage devices and to raise the voltage from generating power station so that the electric power can be transmitted over long distances.
2. The basic function of transformer is to change?
A. the level voltage
B. the level frequency
C. power factor level
D. power level
The main function of the transformer is to transform ac energy from one voltage to another voltage level.
1. Oil is provided in an oil filled transformer for
C. both cooling and insulation.
Answer লেখাতে ক্লিক করলে সঠিক উত্তরটি দেখাবে।
Click “Answer” for correct Answer.
Transformer Oil: Mineral-based
Transformer oil is a mineral-based oil that is commonly used in oil filled transformers for its chemical properties and dielectric strength. This oil in a transformer acts as an insulator and a cooling agent.
EEE Job Math Solutions
No posts found!