What are the possible errors in induction (energy meter) measuring instruments?

What are the possible errors in induction (energy meter) measuring instruments?
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1 Answer

Answer :

a. Phase error: Field flux in induction meter does not lag 90° behind the supply voltage due to its resistance. This can be adjusted by copper shading rings, which are placed at the central limb of the shunt magnet.

b. Speed error: An error in speed, which is tested on the non-inductive load, can be eliminated by correctly adjusting the position of the brake magnet.

c. Friction error: It can be reduced very much by providing two copper shading st the both outer limbs.

d. Creeping error: Some time slow, continuous rotation of the disc (rotor) when only the pressure coil is excited, but no current flowing in the circuit (no current in current coil) may happen. It may be caused due to incorrect friction compensator, stray magnetic field, and excess voltage. This can be rectified by drilling two holes in the disc on the opposite sides of the spindle. This causes sufficient distortion of the field to prevent rotation, when one of the holes comes under one of the pole of the shunt magnet.
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