What is Energy Meter?
The meter that is used for the measurement of the electrical energy utilized by the electrical load such as lamps, induction motors etc in domestic as well as industries is known as the energy meter. In the energy meter, the electrical energy consumed by the load is measured in Kilo Watt-hours.
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| Energy Meter |
In the energy meter, the energy is the total power consumed by the load and is also utilized by the load at a particular interval of time. The basic function of the energy meter is a measurement of power consumption in ac circuits. The energy meter is also known as a watt-hour meter. The energy meter is less costly and accurate in measurement.
Construction of energy meter
The energy meter consists of four parts which are given below
1. Driving system
2. Moving system
3. Braking system
4. Registering system
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| Construction of Energy Meter |
1. Driving system
The driving system consists following parts
1. Shunt electromagnet
2. Series electromagnet
3. Copper shading band
The main part of the driving system is the electromagnet which is a temporary magnet. The electromagnet is excited by the current flowing through the own coil. The core of both the electromagnet has become from the lamination of silicon steel.
The driving system consists of two nos of the electromagnet.
1. Shunt electromagnet
The upper one electromagnet is called a shunt electromagnet. The shunt electromagnet carries a voltage coil. The voltage coil consists of many number of turns of thin wire of copper.
The voltage coil is directly connected with the supply and the current through the voltage coil is proportional to the shunt voltage. The voltage coil of the energy meter produces a high ratio of inductance to resistance.
2. Series electromagnet
The lower one electromagnet is called a series electromagnet. The series electromagnets carry two nos of the current coil. The current coil consists of less number of turns of thin wire.
The current coil of the energy meter is connected in series with the load circuit. The current consumed by the load is passing through it.
3. Copper shading band
The lower part of the shunt electromagnet consists of one copper shading band. The shading band is used to provide the frictional compensation and also used to align the shunt electromagnet flux in such a way that the phase angle between the shunt magnetic flux and supply remains exactly 90 degrees.
2. Moving system
The moving system consists of an aluminium disc. The aluminium disc is mounted on the vertical shaft. The aluminium disc is placed between the air gap of two electromagnets. The electromagnets produced the magnetic flux when the load consume the power. This flux is cut by the aluminium disc and eddy currents are produced in the aluminium disc.
Due to interference of eddy current which is induced on the aluminium disc and magnetic flux produced by the two electromagnet produced the deflecting torque on the aluminium disc. As a result of deflecting torques, the aluminium disc starts rotating.
When the load consume power, the aluminium disc starts rotating and after several rotations of aluminium, the disc displays the power consumption by the load, in a particular time interval. The aluminium disc measure power consumption by the load in Kwh(kilowatt-hour).
3. Braking system
The permanent magnet is used in the braking system of the energy meter which is called a brake magnet. The brake magnet is used for reducing the rotation of the aluminium disc. The permanent magnet is placed on the aluminium disc.
When the aluminium disc rotates between the magnetic flux of two electromagnets, an eddy current is induced in the aluminium disc and this eddy current is cut by the magnetic field produced by the permanent magnet. As a result braking torque is produced on the disc.
This braking torque opposes the movement of the aluminium disc and hence the speed of the aluminium disc is reduced. The braking torque is changed by changing the position of the permanent magnet on the aluminium disc. The speed of the aluminium disc is also controlled by controlling the changing flux.
4. Registering system
The registering system is used for recording the number of rotations of the aluminium disc which is directly proportional to the power consumed by the load in kilowatt-hours.
The aluminium disc has one spindle. The disc spindle is driven by the gear on the aluminium disc shaft which indicates the number of times the disc rotates.
Working of energy meter
The aluminium disc is placed between the ait gap of two electromagnets like one is a series magnet and another is a shunt magnet. The series magnets consist of the current coil and shunt magnets consist of the voltage coil.
The pressure coil of the electromagnet produces the magnetic flux due to the supply voltage and the current coil produces the magnetic field due to the current drawn by the load.
The magnetic field produced by the voltage coil is lagging 90 degrees from the magnetic field produced by the current coil. As a result, an eddy current is induced on the aluminium disc.
Due to the interaction between the eddy current on the aluminium disc and the magnetic field produced by the two electromagnets, deflecting is produced on the disc.
When the power is consumed by the load, the disc is rotating and after some number of rotations, the aluminium disc displays the unit in kilowatt-hour consumed by the load.
The permanent is used for controlling the speed of the aluminium disc which is called a braking magnet. The deflecting torque on the aluminium disc is proportional to the current in the current coil and the voltage of the voltage coil.
The aluminium disc is connected to the spindle. The disc spindle is driven by the gear on the disc shaft which indicates the number of times the disc rotates. The disc rotation is measured in kilowatt-hours.
Advantages of energy meter
1. The energy meter is used for a long time without any maintenance.
2. The energy meter is less expensive and used for the measurement of alternating current.
3. The energy meter consists of high torque to weight ratio.
4. The energy meter can be used for the measurement of power for a wide range of power.
Disadvantages of energy meter
1. Due to rotating parts in the energy meter, there is an error taking place in the energy meter.
2. The energy meter works on the principle of induction and the induction principle only works on the alternating current. so the energy meters are limited to ac measurement. The energy meter is not used for direct current measurement.