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Supply voltage in an energy meter is
Constant always
Zero always
Depends on the load
Can fluctuate
Can fluctuate
In practical power distribution networks, the supply voltage provided to an energy meter is not ideal and can fluctuate due to load variations, line impedance, and system disturbances. While the pressure coil of an energy meter is designed for a nominal voltage (e.g., 230 V), the actual system voltage fluctuates within permissible limits defined by grid standards.
In practical power distribution networks, the supply voltage provided to an energy meter is not ideal and can fluctuate due to load variations, line impedance, and system disturbances. While the pressure coil of an energy meter is designed for a nominal voltage (e.g., 230 V), the actual system voltage fluctuates within permissible limits defined by grid standards.
TdтАЛтИЭVтЛЕIcos╧Х тАФ Driving torque in single-phase induction type energy meter
E=тИлVтЛЕIcos╧ХтЛЕdt тАФ Total electrical energy registered by the meter
The energy meter operates on the principle of electromagnetic induction, where the driving torque TdтАЛтИЭVIcos╧Х. The pressure coil (voltage coil) is connected directly across the supply lines. As system loads vary dynamically across the grid, the resulting IR and IX drops along transmission and distribution lines cause the supply voltage at the consumer terminals to fluctuate.
The pressure coil (voltage coil) has high inductance and is connected in parallel with the supply.
Grid codes usually allow voltage fluctuations within a specified tolerance band (e.g., ┬▒6% in Indian Electricity Rules).
Friction and braking torque compensations are designed considering voltage fluctuations to minimize registration errors.
Single-phase and three-phase domestic and industrial energy metering.
Power quality and voltage profiling monitoring systems.
Option A (Constant always) is incorrect because real utility supply grids experience voltage regulation drops under varying load conditions.
Option B (Zero always) is incorrect because zero voltage implies no power delivery and zero driving torque.
Option C (Depends on the load) is incomplete/misleading; while terminal voltage drops depend on load current, voltage is primarily determined by grid supply and naturally fluctuates irrespective of local load alone.
D is correct тАФ The AC supply voltage connected across the energy meter pressure coil can fluctuate due to dynamic grid loading and transmission line voltage drops.
In energy meter error analysis, remember that voltage fluctuations alter the driving torque TdтАЛ, leading to potential over-registration or under-registration unless compensated.