Transformers Questions & Answers
Transformer Losses and Efficiency
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The load current at which maximum efficiency occurs is independent of the load power factor.
Correct!
Wrong!

Core losses of a transformer as a function of frequency is best approximated by which of the below characteristics?
Correct!
Wrong!

1. I. Maximum voltage regulation occurs at the leading p.f.
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are correct regarding the transformer?
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are correct regarding the transformer?
Correct!
Wrong!

It is possible to attain maximum efficiency in a transformer when the
Correct!
Wrong!

Mutual flux ______ at the lagging loading and it _____ at the leading power factor.
Correct!
Wrong!

I. Maximum voltage regulation occurs at the leading p.f.
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are incorrect regarding the transformer?
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are incorrect regarding the transformer?
Correct!
Wrong!

The full load voltage drop in a 1phase transformer is 2% and 4% respectively due to resistance and leakage reactance. Then the voltage drop is maximum at
Correct!
Wrong!

The full load voltage drop in a 1phase transformer is 2% and 4% respectively due to resistance and leakage reactance. Then the voltage drop is zero at
Correct!
Wrong!

The efficiency of a 20 KVA, 2000/200 V, single phase transformer at unity pf is 98%. The the total losses at this condition is
Correct!
Wrong!

I. Maximum voltage regulation occurs at the leading p.f.
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are incorrect regarding the transformer?
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are incorrect regarding the transformer?
Correct!
Wrong!

From the above graph of the core losses per cycle is, the hysteresis losses per phase for a transformer at a operating frequency of 40 Hz is
Correct!
Wrong!

Which of the below mentioned losses occur in a transformer?
Correct!
Wrong!

From the above graph of the core losses per cycle is, the eddy losses per phase for a transformer at a operating frequency of 40 Hz is
Correct!
Wrong!

The efficiency of a 20 KVA, 2000/200 V, single phase transformer at unity pf is 98%. The given total losses at full load is 200 W. The pu resistance is
Correct!
Wrong!

The efficiency of a transformer can be calculated accurately from
Correct!
Wrong!

I. Maximum voltage regulation occurs at the leading p.f.
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are correct regarding the transformer?
II. Maximum voltage regulation occurs when load p.f. angle and impedance angle of the leakage impedance are same.
III. V.R. at zero p.f. is always zero.
IV. V.R. of a transformer may be negative at leading p.f.
Which of the statements made here are correct regarding the transformer?
Correct!
Wrong!
