Correct Answer - Option 1 : 480 V

__Concept:__

EMF equation of a DC Generator:

As the armature rotates, a voltage is generated in it’s coils, which is called Generated EMF or Armature EMF and is denoted by Eg.

\({E_g} = \frac{{\phi ZNP}}{{60A}}\)

Where,

Eg = Generated Emf

P = Number of poles of the machine

ϕ = flux per pole in weber

Z = total number of armature conductors

N = speed of armature in revolution per minute (r.p.m)

A = number of parallel paths in the armature winding

The number of parallel Paths:

A = P ⋅ m

Where,

m = multiplexity (simplex/duplex)

In wave winding, multiplexity is always 2 (two)

Therefore A = 2P

While in lap winding, there are two types:

- Simplex Lap winding : m = 1

- Duplex Lap winding : m = 2

NOTE:

If multiplexity is not mentioned, then always take simplex lap winding i.e. m = 1

__Calculation:__

Given:

P = 4

ϕ = 20 mWb per pole

N = 1000 rpm

∴ No. of conductors (Z) = 720

A = 2

We know:

\({E_g} = \frac{{\phi ZNP}}{{60A}}\)

\({E_g} = \frac{{0.02 \times 720 \times 1000 \times 4}}{{60 \times 2}}\)

Eg = 480 V