Transformers Questions & Answers
Equivalent Circuit of Transformer
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A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 Ω, X=6 Ω
LV: r = 0.03 Ω, X = 0.07 Ω
The primary reactance referred to secondary is
HV : r = 2.4 Ω, X=6 Ω
LV: r = 0.03 Ω, X = 0.07 Ω
The primary reactance referred to secondary is
Correct!
Wrong!

If a transformer is fed from a dc rather than a 1phase ac supply, then the transformer will
Correct!
Wrong!

A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 Ω, X=6 Ω
LV: r = 0.03 Ω, X = 0.07 Ω
The primary resistance referred to secondary is
HV : r = 2.4 Ω, X=6 Ω
LV: r = 0.03 Ω, X = 0.07 Ω
The primary resistance referred to secondary is
Correct!
Wrong!

There are two identical transformers A and B such that flux density applied to B is doubled. Then magnetizing current of B is
Correct!
Wrong!

A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 Ω, X=6 Ω
LV: r = 0.03 Ω, X = 0.07 Ω
The secondary resistance referred to primary is
HV : r = 2.4 Ω, X=6 Ω
LV: r = 0.03 Ω, X = 0.07 Ω
The secondary resistance referred to primary is
Correct!
Wrong!

In a transformer if the frequency of the supply is varied then the magnetizing current in the core also varies.
Correct!
Wrong!

CRGO Laminations in a transformer are used to minimize
Correct!
Wrong!

A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 Ω, X=6 Ω, Primary
LV: r = 0.03 Ω, X = 0.07 Ω, Secondary
The secondary reactance referred to primary is
HV : r = 2.4 Ω, X=6 Ω, Primary
LV: r = 0.03 Ω, X = 0.07 Ω, Secondary
The secondary reactance referred to primary is
Correct!
Wrong!

The flux involved in the emf equation of a transformer has
Correct!
Wrong!

In a transformer ______ decreases with increase of the leakage flux.
Correct!
Wrong!

I. Core flux – Depends on applied voltage
II. Leakage flux – Depends on winding current
Which of the above two are not matched correctly?
II. Leakage flux – Depends on winding current
Which of the above two are not matched correctly?
Correct!
Wrong!

For a single phase transformer operating at normal operating conditions has useful flux of 1 Wb. If the machine is loaded at 0.8 p.f., then its mutual flux
Correct!
Wrong!

The components needed to draw the phasor diagram of the transformer is
A. load current, B. Equivalent circuit parameters, C. Load power factor
A. load current, B. Equivalent circuit parameters, C. Load power factor
Correct!
Wrong!

If the frequency at the primary supply is varied gradually, then the secondary terminal voltage will
Correct!
Wrong!

A single phase transformer has emf per turn having 2310/220 V, 50Hz transformer as 13 V. The core area is(in square cm)
Correct!
Wrong!

A single phase transformer has emf per turn having 2310/220 V, 50Hz transformer as 13 V. Then the estimated primary turns will be
Correct!
Wrong!
