Question

In an induction type energy meter, the steady speed attained by the rotating disc is

1. Proportional to the deflecting torque.

2. Proportional to the resistance of the path of eddy currents.

3. Inversely proportional to the effective readings of disc from its axis.

4. Inversely proportional to the square of brake magnet flux

Which of the above are correct?
1. 1, 2 and 3 only
2. 1, 2 and 4 only
3. 2, 3 and 4 only
4. 1, 2, 3 and 4

Answer 1

Correct Answer - Option 4 : 1, 2, 3 and 4

Induction type energy meter works on electromagnetic induction. The disc of the energy meter is placed in the air gap of the two electromagnets. Due to the interaction of the flux through there magnets, disc induces the deflection torque.

Now, the speed of rotation of the disc is

\(N \propto \left( {\frac{r}{{{\phi ^2}}}} \right) \times {T_D} \times \frac{1}{x}\) 

Where,

T_D = deflecting torque

r = resistance of path of eddy current

x = reading of disc from its axis

ϕ = brake magnet flux