Questions
21
In a transformer the tappings are generally provided on
Answer: low voltage side
22
If the percentage impedances of the two transformers working in parallel are different, then
Answer: parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load
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23
What will happen if the transformers working in parallel are not connected with regard to polarity ?
Answer: Incorrect polarity will result in dead short circuit
24
If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be
Answer: R2IK2
25
Two transformers operating in parallel will share the load depending upon their
Answer: per unit impedance
27
The purpose of providing iron core in a step-up transformer is
Answer: to decrease the magnitude of mag-netizing current
28
Greater the secondary leakage flux
Answer: less will be the secondary induced e.m.f.
29
Spacers are provided between adjacent coils
Answer: to provide free passage to the cooling oil
30
No-load current of a transformer has
Answer: has small magnitude and low power factor
32
The maximum efficiency of a distribution transformer is
Answer: at 50% full load
33
Power transformers are designed to have maximum efficiency at
Answer: nearly full load
34
Natural oil cooling is used for transformers up to a rating of
Answer: 3000 kVA
35
In the transformer the function of a conservator is to
Answer: protect the transformer from damage when oil expends due to heating
37
The no load current in a transformer lags behind the applied voltage by an angle of about
Answer: 75°
39
In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are
Answer: hysteresis and eddy current losses
