Induction Type Energy Meter

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Construction of Induction Type Energy meter

Four main parts of operating mechanism

1. Driving system

2. Moving system

3. Braking system

4. Registering system

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Driving System

• Consists of two electromagnets• The core laminated with silicon steel• One current coil and voltage (pressure)

coil• Magnets are called series and shunt

magnets• Cu bands are used on centre limb of

shunt magnet to make flux in quadrature to voltage

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Moving System

• This consists of an aluminum disc mounted on a light alloy shaft

• Disc between series and shunt magnets • Supported by jewel bearing

• A gear mechanism is connected to the shaft

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Braking System• A permanent magnet positioned near the edge of the aluminum disc forms the braking system

• Braking torque is provided during disc movement

•The position of the permanent magnet is adjustable, and therefore braking torque can be adjusted by shifting the permanent magnet to different radial positions

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Counting system

• The function is to register the energy consumed

• Energy consumed is directly proportional to the number of revolutions of the disc

•The gear mechanism rotate round dials, which are marked with ten equal divisions

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1.Voltage coil, C22.Current coil, C13.Stator -

concentrates and confines magnetic field

4.Aluminum disc, D5.Brake magnets6.Gear mechanism7.Display dials

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Assignment

1) A dynamometer type wattmeter with its voltage coil connected across the load side of the instrument reads 250 W. If the load voltage were 200 V, what is the power being taken by the load? The voltage coil has a resistance of 2000 Ω (Ans: 230 W)

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2) The resistance of the coils of a wattmeter are 0.01 Ω and 1000 Ω respectively and both are non inductive. The load current is 20 A and the voltage applied to the load is 30 V. Show the two ways in which the voltage coil can be connected and find the error in the reading in each case

(Ans :0.67%, 0.15%)