Question

The generated emf per parallel path in armature of a DC Generator is:

1. Directly proportional to flux

2. Inversely proportional to number of poles

3. Directly proportional to rotational speed of armature

Which of these is / are correct?

1. 2 and 3
2. Only 2
3. 1 and 2
4. 1 and 3

Answer 1

Correct Answer - Option 4 : 1 and 3

The generated emf per parallel path in the armature of a DC Generator is given by

E = \(\frac{ϕ \ P\ N}{60}\times\frac{Z}{A}\)

where,

ϕ = flux per pole

P = number of poles

N = Rotational speed in rpm

Z = number of conductors

A = number of parallel paths

Therefore, Generated EMF(E) is directly proportional to flux(ϕ ),

rotational speed(N), and Number of poles(P).

Back EMF in DC Motor:

• When the current-carrying conductor placed in a magnetic field, the torque induces on the conductor, the torque rotates the conductor which cuts the flux of the magnetic field.
• According to the Electromagnetic Induction Phenomenon “when the conductor cuts the magnetic field, EMF induces in the conductor”.
• It is seen that the direction (Right hand rule) of the induced emf is opposite to the applied voltage. Thereby the emf is known as the counter emf or back emf.