Question

Creep error may occur induction type energy meter due to
1. incorrect position of brake magnet
2. incorrect adjustment of position of shading band
3. overvoltage across voltage coil
4. increase in temperature

Answer 1

Correct Answer - Option 3 : overvoltage across voltage coil

• Creeping in the induction type energy meter is the phenomenon in which the aluminum disc rotates continuously when only the voltage is supplied to the pressure coil and no current flows through the current coil.
• It is the kind of error in which the energy meter consumes a very small amount of energy even when no load is attached to the meter.
• The creeping increases the speed of the disc even under the light load condition which increases the meter reading. Vibration, stray magnetic field and the extra voltage across the potential coil are also responsible for the creeping.
• The creeping error occurs because of excessive friction. The main driving torque is absent at no load. Hence the disc rotates because of the additional torque provided by the compensating vane.

 

• In order to prevent this creeping on no-load two holes or slots are drilled in the disc on opposite sides of the spindle
• This causes sufficient distortion of the field; The result is that the disc tends to remain stationary when one of the holes comes under one of the shunt magnets