UPPCL EE :Electrical Machines Quiz 2

A four-pole d.c. machine armature has 54 slots. It is lap-wound with single-turn coils. How many armature coils are required?

In which of the following winding we don’t use equaliser ring?

Choose the correct statement related to DC shunt motor speed control.

S1: By reducing armature supply voltage (But not below rated values), speed can be reduced below rated speed.

S2: By reducing field current, speed can be reduced below rated speed.

In a DC machine, armature MMF is

For DC shunt motor, to increase speed above the rated speed.

1. Flux per pole can be reduced.

2. Field current can be reduced.

Choose the correct option:

In a DC compound motor operating at rated voltage & rated torque. If the series winding is shorted, then what will be effect on speed of motor?

A, 4 pole lap connected DC motor supplying a load of 5 kW at 100 V. Its armature consists of 800 conductors. If the brush displacement is 5° then what is the demagnetising mmf/pole?

A DC generator has armature emf of 200 V when it works on full flux/pole 40 mWb, and speed of 500 rpm. The generated emf at a speed of 1000 rpm & flux/pole 20 mWb is

In a lap winding, there are always as many paths in parallel through the armature winding as there are a number of poles. In such a lap winding, the current in each armature coil is

A DC generator with a 12 pole, triplex lap winding excited with a flux/pole of 6.2 × 10^-2 wb. The generator speed is 80 rpm, and it uses 420 coils of 20 turns each the total generated emf is __________ volts.