Electromechanical induction type Energy meter
An electricity meter, electric meter, electrical meter, or energy meter is a device that measures the amount of electric energy consumed by a residence, a business, or an electrically powered device.
It is the popularly known and most common type of age old watt hour meter. It consists of rotating aluminum disc mounted on a spindle between two electro-magnets. Speed of rotation of disc is proportional to the power and this power is integrated by the use of counter mechanism and gear trains in. It comprises of two silicon steel laminated electromagnets i.e., series and shunt magnets.
Series magnet carries a coil which is of few turns of thick wire connected in series with line whereas shunt magnet carries coil with many turns of thin wire connected across the supply.
Breaking magnet is a permanent magnet which applies the force opposite to normal disc rotation to move that disc at balanced position and to stop the disc while power is off.
The working of single phase induction type energy meters are based on two main fundamentals:
i. Rotation of aluminum disk.
ii. Arrangement of counting and displaying the amount of energy consumed.
Rotation of an Aluminum Disk:
The rotation of metallic disk is operated by two coils. Both the coils are arranged in such way that one coil produces a magnetic field in proportion to voltage and the other coil creates a magnetic field proportion to current. The field produced by voltage coil is delayed by 90° so that eddy current is induced in the disk. The force exerted on the disk by the two fields is proportional to the product of the immediate current and voltage in the coils.
As a result of it, a lite weight aluminum disk rotates in an air gap. But there is a need to stop a disk when there is no power supply. A permanent magnet works as a brake which opposes the rotation of the disk and balances the speed of rotation with respect to power consumption.
Arrangement of Counting and Displaying the Energy Consumed:
In this system, the rotation of the floating disk has been counted and then displayed on the meter window. The aluminum disk is connected to a spindle which has a gear. This gear drives the register and the revolution of the disk has been counted and displayed on the register which has series of dials and each dial represent a single digit. There is a small display window in the front of the meter which displays the reading of energy consumed with the help of dials. There is a copper shading ring at the central limb of the shunt magnet. To make the phase angle between flux produced by shunt magnet and supply voltage about 900, small adjustments in the place of the ring is required.
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