physics 1.1

Question

1.1. Calculate the speed of a four-pole series generator having a wave-wound armature with 315 conductors and resistance of 0.6 ohm supplying a load of 50 kW at 1000 V. The resistance of the field-winding brush contact resistance is 0.4 ohm. The field sets up a flux per pole of 0.1 Wb.   

Comments

Why is the number of poles 4 and not 2. Are we not dividing 4 by 2?

Answer 1

(1.1)

Step 1:

For a four pole generator :

The number of conductors Z  is 315 conductors.

Armature resistance is 0.6 .

Brush resistance is 0.4 .

The total armature resistance R_a is 0.6 + 0.4 = 1 .

Flux per pole is 0.1 Wb.

DC generator supplies load of 50 kW at 1000 v.

Armature current is .

The EMF of a DC generator : ,

is the emf of the DC Generator.

.

where Z  is the number of conductors.

N  is the speed of the DC generator.

is the magnetic flux.

P  is the number of magnetic poles.

a is the number of parallel circuits.

Step 2:

Calculate the emf of the DC Generator.

Emf of the DC Generator is 950 v.

EMF of a DC generator : .

For a four pole generator : P = 4

For wave wound winding : a = 2

Speed of the DC generator is 905 rpm.

Solution :

Speed of the DC generator is 905 rpm.