Question

Self braking action is minimised by _________

(a) maintaining high speed for disc

(b) maintaining medium speed for disc

(c) keeping the disc at rest

(d) maintaining low speed for disc

The question was posed to me in an international level competition.

I would like to ask this question from Friction and Overload Compensation in chapter Measurement of Power and Related Parameters of Electrical Measurements

Answer 1

Right option is (d) maintaining low speed for disc

To explain: In an energy meter we can minimise or eliminate the self braking action by keeping the disc speed as low as possible at full load condition. This is achieved by maintaining the flux due to the current coil smaller than that due to the shunt coil. The figure below shows the compensating device.