Under which of the following conditions hunting of synchronous motor is likely to occur ?
Over-excitation
Over-loading for long periods
Periodic variation of load
Small and constant load
Periodic variation of load
No-load on a transformer is carried out to determine
magnetizing current and loss
efficiency of the transformer
magnetizing current
copper loss
magnetizing current and loss
Sumpner’s test is conducted on transformers to determine
temperature
all-day efficiency
stray losses
none of the above
temperature
The path of a magnetic flux in a transformer should have
low resistance
low reluctance
high resistance
high reluctance
low reluctance
The dielectric strength of transformer oil is expected to be
33 kV
lkV
100 kV
330 kV
33 kV
The permissible flux density in case of cold rolled grain oriented steel is around
4.7 Wb/m2
3.7 Wb/m2
2.7 Wb/m2
1.7 Wb/m2
1.7 Wb/m2
Material used for construction of transformer core is usually
wood
copper
silicon steel
aluminium
silicon steel
No-load current in a transformer
lags behind the voltage by about 75°
leads the voltage by about 15°
lags behind the voltage by about 15°
leads the voltage by about 75°
lags behind the voltage by about 75°
The efficiency of a transformer will be maximum when
copper losses = iron losses
hysteresis losses = eddy current losses
copper losses = hysteresis losses
eddy current losses = copper losses
copper losses = iron losses
Which winding in a transformer has more number of turns ?
Secondary winding
High voltage winding
Low voltage winding
Primary winding
High voltage winding
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