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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Driving system in an induction type single phase energy meter consists of
One magnet
Two electromagnets
Five electromagnets
Ten magnets
Two electromagnets
Quick Summary: The driving system of a single-phase induction-type energy meter consists of two separate electromagnets: the series magnet (current coil) and the shunt magnet (potential coil). These electromagnets create the necessary magnetic fields that interact to induce eddy currents in the rotating aluminum disc.
The driving system of a single-phase induction-type energy meter consists of two separate electromagnets: the series magnet (current coil) and the shunt magnet (potential coil). These electromagnets create the necessary magnetic fields that interact to induce eddy currents in the rotating aluminum disc.
Td∝ΦpΦssinα — where Td is driving torque, Φp is shunt flux, Φs is series flux, and α is the phase angle.
P=VIcosϕ — the power being measured by the interaction of these two electromagnets.
The shunt magnet is connected across the supply and carries a current proportional to the supply voltage, creating a magnetic flux Φp. The series magnet is connected in series with the load and carries the load current, creating flux Φs. The interaction of these fluxes with the eddy currents induced in the disc produces a driving torque proportional to the real power P=VIcosϕ, causing the disc to rotate.
The shunt magnet has many turns of fine wire (high inductance).
The series magnet has few turns of thick wire (low resistance).
The phase difference between the two fluxes is ideally 90°.
The torque produced causes the disc to rotate at a speed proportional to the power consumed.
Low cost and rugged construction.
Good damping torque integration.
Ability to measure energy over a long period.
Affected by variations in voltage and frequency.
Presence of friction error requiring compensation.
Domestic energy consumption measurement.
Industrial energy metering.
The shunt magnet is also known as the potential coil or pressure coil.
The series magnet is also known as the current coil.
Option A is incorrect because one magnet cannot produce the required phase-shifted rotating field interaction; Option C and D refer to numbers of magnets not used in standard single-phase meters.
B is correct — The driving system comprises two distinct electromagnets: a shunt magnet (potential coil) and a series magnet (current coil).
Always remember that in an induction meter, the shunt flux is made to lag the supply voltage by exactly 90° using a shading band, which is crucial for accurate power measurement.