A cumulatively compounded long shunt motor isdriving a load at rated torque and rated speed.If the series field is shunted by a resistance equalto the resistance of the series field keeping the torque constant,
The efficiency of a power transformer is around
When voltage is transformed from primary to secondary then it is _____.
If the applied voltage to a transformer primary isincreased by keeping the V/f ratio fixed, then the magnetizing current and the core loss will,respectively:
The applied voltage of a certain transformer isincreased by 75%; while the frequency of the applied voltage is reduced by 25%. The maximum core flux density will :
On no-load phasor diagram of transformer, thecore loss component of the current remains in phase with
At which condition of the transformer theequivalent circuit will be as shown in the figure ?
In a transformer, zero voltage regulation at full load s:
While performing the open-circuit and shortcircuit tests on a transformer to determine parameters the status of the low voltage (LV) and high voltage (HV) windings will be such that
A 2 kVA transformer has iron loss of 150 Wand full-load copper loss of 250 W. Themaximum efficiency of the transformer wouldoccur when the total loss is
Grain oriented laminated sheet steel intransformer reduces
The colour of fresh dielectric oil used intransformers is
Transformer oil must be free from
Conservator (for transformer) is used
The noise, in a transformer, caused by vibrationsof laminations set by magnetic forces, is termed as
Distribution transformers have core losses
In Scott connection, if the turns ratio of main transformer is K,
The copper loss is constant for
Current-versus time graph for an idealcommutation is a
The dummy coils in d.c. machines re useful to
In a series wound d.c. machine (generator ormotor), the series field winding consists of
A d.c. shunt motor takes 5A at 100 V whenrunning light. shunt field resistance is 50W and armature resistance is 0.2W. What is the driving power ?
If the applied voltage to a dc machine is 230 V, then the back emf, for maximum power developed, is
The armature resistance of a 6-pole lap woundgenerator is 0.05W. If the armature is rewoundusing a wave winding, the armature resistancewill be
A 4-pole, 500 V shunt motor has 720 wave connected conductors on its armature. The fullloadarmature current is 60 A and flux per poleis 0.03 Wb. The armature resistance is 0.2Wand contact drop per brush is 1V. What is the back e.m.f ?