energymeter.ppt

Energy Meter

Presented by:

Aziz Ahmad Haider Reg # 2011-EE-458

Contents:

What is an energy meter?Why it is used?What is the working Principle of the energy meter? Which Components are used in an energy meter ?What are the Advantages and disadvantages of usual energy meters?What is the Solution for the drawbacks of commonly used energy meters?

Energy meter

An energy meter is a device that measures the amount of electrical energy consumed by a residence, business, or an electrically powered device.

What is the energy?

Energy is the product of power and time for which power is used i.e

Energy=power×time

Induction watt hour meter(Energy meter) which are commonly used measure electrical energy in KWH(killo watt-hour)

Components

Schematic Diagram

Working principle:

It involve four steps in it’s workingDriving forceMoving systemBreaking system Registering system

Moving systemEnergy meter has a moveable Aluminum disk in it which is mounted on a vertical shaft.

The rotation of this disk is base of energy measurement

Driving systemWhen a load is connected poles of potential and the current coils produces their magnetic field because of flow of current which produce resultant flux .

This resultant flux develops eddy current inside the disk.So that disk starts to rotate as

“Current carrying conductor placed inside a magnetic field will experience a force called Lorenze force.”

Operation

BreakingWhy Breaking is require?

When the disk start to rotate it is under a torque and that torque is depend upon current in coil so for a large load their will be very high torque and speed of the Aluminum disk is also very high which produce different mechanical loses(e.g go to run away, disk become frictionless) therefore we require a retarding torque to prevent from these loses.

For this purpose permanent magnets are used in energy meter across the disk.

Working of permanent magnets

Flux of the permanent magnets is cut because of motion of Al-disk that produce additional eddy current. This eddy current will develop it’s own torque that is opposite to the driving torque.

And

Retarding torque produced by permanent magnets is directly proportional to speed of the disk so that

High for heavy loads and less for small loads.

At what speed disk rotates?

Disk should rotate on a speed value where

Driving torque=retarding torque

Registering systemThe amount of energy is being displayed by using the mechanical counter which are in couple with the shaft through a gear train.

How the mechanical counters are coupled

Draw backs Incorrect magnitude of fluxes, Incorrect phase angles, Changes in strength of brake magnet, Changes in disc resistance, Abnormal friction of moving parts

SolutionsTo avoid disk resistance and abnormal friction(appears with time) we have to replace our meters after a specific time duration for accurate reading.

For incorrect magnitudes of fluxes and

Phase angles we can use creep or low load adjustment.

Another solutionBesides of replacing meters our adjust them

on low load we can use Smart Energy meters

Which are more accurate and also have long life with no frictional loses.

Internal scheme of smart Energy meters

Benefits of Smart Energy meterBetter AccuracyLow Current PerformanceLow voltage performanceDifficult to temperDigital display