Question

Consider a 6 pole DC generator having 300 conductors and is rotating at a speed of 500 rpm. The flux per pole is 20 mWb. What will be the induced voltage, If the winding type is wave connected?
1. 50 V
2. 100 V
3. 150 V
4. 250 V

Answer 1

Correct Answer - Option 3 : 150 V

Concept:

EMF equation of a DC Generator:

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

\({E_g} = \frac{{ϕ ZNP}}{{60A}}\)

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 (rpm)

A = number of parallel paths in the armature winding

Also,

A = P⋅m

Where,

m = multiplexity (simplex/duplex)

In wave winding, multiplexity is always 2 (two)

Therefore, A = 2

While in lap winding, there are two types:

1. Simplex Lap winding: m = 1

          ∴ A = P

2. Duplex Lap winding: m = 2 

         ∴ A = 2P

Note:

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

Calculation:

Given that,

Number poles P = 6

Conductors Z = 3000

Speed N = 500 rpm

The flux per pole (ϕ) = 20 × 10-3 Wb

As winding is wave type 

Number of parallel paths A = 2

⇒ Induced or generated emf = (20 × 10-3 × 500 × 300 × 6) / (60× 2) = 150 V