UNIT-1

SYLLABUS

GE2151 BASIC ELECTRICAL AND ELECTRONICS ENGINEERING

L T P C

(COMMON TO BRANCHES UNDER CIVIL, MECHANICAL AND TECHNOLOGY

FACULTY) 3 0 0 3

UNIT I ELECTRICAL CIRCUITS & MEASURMENTS

12

Ohms Law Kirchhoffs Laws Steady State Solution of DC Circuits

Introduction to AC Circuits Waveforms and RMS Value Power and PowerIntroduction to AC Circuits Waveforms and RMS Value Power and Power

factor Single Phase and Three Phase Balanced Circuits. Operating

Principles of Moving Coil and Moving Iron Instruments (Ammeters and

Voltmeters), Dynamometer type Watt meters and Energy meters.

UNIT II ELECTRICAL MECHANICS

12

Construction, Principle of Operation, Basic Equations and Applications

of DC Generators, DC Motors, Single Phase Transformer, single phase

induction Motor.

Dr.R.Anushya,SRREC,Padur

UNIT III SEMICONDUCTOR DEVICES AND APPLICATIONS 12

Characteristics of PN Junction Diode Zener Effect Zener Diode and its Characteristics Half wave and Full wave Rectifiers Voltage Regulation.

Bipolar Junction Transistor CB, CE, CC Configurations and Characteristics Elementary Treatment of Small Signal Amplifier.

UNIT IV DIGITAL ELECTRONICS 12

Binary Number System Logic Gates Boolean Algebra Half and Full Adders Flip-Flops Registers and Counters A/D and D/A Conversion (single concepts)

UNIT V FUNDAMENTALS OF COMMUNICATION ENGINEERING 12

Types of Signals: Analog and Digital Signals Modulation and Demodulation: Principles ofTypes of Signals: Analog and Digital Signals Modulation and Demodulation: Principles ofAmplitude and Frequency Modulations. Communication Systems: Radio, TV,

Fax, Microwave, Satellite and Optical Fibre (Block Diagram Approach only).

TOTAL : 60 PERIODS

REFERENCES:

1. Muthusubramanian R, Salivahanan S and Muraleedharan K A, Basic Electrical, Electronics and Computer Engineering,Tata McGraw Hill, Second Edition, (2006).

2. Nagsarkar T K and Sukhija M S, Basics of Electrical Engineering, Oxford press (2005).

3. Mehta V K, Principles of Electronics, S.Chand & Company Ltd, (1994).

4. Mahmood Nahvi and Joseph A. Edminister, Electric Circuits, Schaum Outline Series, McGraw Hill, (2002).

5. Premkumar N, Basic Electrical Engineering, Anuradha Publishers, (2003).


Ohm's law


Ohm's law states that the current througha conductor between two points isdirectlyproportional to the potentialdirectlyproportional to the potentialdifference across the two points. Introducingthe constant of proportionality,the resistance,[1] one arrives at the usualmathematical equation that describes thisrelationship:[2]


In circuit analysis, three equivalent

expressions of Ohm's law are used

interchangeably:


Introduction Fundament laws that govern electric circuits:

Ohms Law.

Kirchoffs Law.

These laws form the foundation upon which electric circuit analysis is built.

Common techniques in circuit analysis and design:

Combining resistors in series and parallel.

Voltage and current divisions.

Wye to delta and delta to wye transformations.

These techniques are restricted to resistive circuits.


Ohms Law

v=iR

*pay careful attention

to current direction

v=iR


Value of R :: varies from 0 to infinity

Extreme values == 0 & infinity.

Only linear resistors obey Ohms Law.

Short circuitShort circuit Open CircuitOpen Circuit


Power:

P = iv i ( i R ) = i2R wattsP = iv i ( i R ) = i R watts

(v/R) v = v2/R watts


Nodes, Branches & Loops

Elements of electric circuits can be interconnected in several way.

Need to understand some basic concepts of network topology.

Branch: Represents a single element

(i.e. voltage, resistor & etc)

Node: The meeting point between two or more branches.

Loop: Any closed path in a circuit.Dr.R.Anushya,SRREC,Padur


Determine how many branches and

nodes for the following circuit.



5 Branches

1 Voltage Source

1 Current Source

3 Resistors

3 Nodes

a

b

c

DKS1113 Electric CircuitsDr.R.Anushya,SRREC,Padur

Kirchoffs Laws Kirchoffs Current Law (KCL)

The algebraic sum of current entering / leaving a

node (or closed boundary) is zero.

Current enters = +ve

Current leaves = -ve

current entering = current leavingDr.R.Anushya,SRREC,Padur

Example 5:

Given the following circuit, write the equation for

currents.


Use KCL to obtain currents i1, i2,

and i3 in the circuit.


Kirchoffs Voltage Law (KVL)

Applied to a loop in a circuit.

According to KVL The algebraic sum of voltage (rises and drops) in a loop is zero.

+

-

+ v1 -

- v3 +

+

V2

-

vs


Use KVL to obtain v1, v2 and v3.


Kirchoffs Laws

Example 12:

Calculate power dissipated in 5 resistor.

10

DKS1113 Electric CircuitsDr.R.Anushya,SRREC,Padur

Learning Goals - we will learn: How to simplify resistors connected in a circuit in series and in parallel.

How to simplify and analyze more complicated networks using Kirchhoffs Rules.Kirchhoffs Rules.

R-C circuits


Series connection

Resistors connected in a circuit in series or parallel can be simplified using the following:

Parallel connection


These complex circuits cannot be reduced to series parallel combinations. So use Kirchhoffs Rules:

1.1.1.1. Ij = 0 junction rule(valid at any junction); conservation of chargeconservation of charge

2.2.2.2. (Vj ) = 0 loop rule(valid for any closed loop); conservation of energy


At node A, Iin = IoutI1 + I3 = I2

Vrises = VdropsLoop #1:

I2R2 +4+ I1R1 = 1 + 2Loop #2:Label: I2R2 +4+ I1R1 = 1 + 2Loop #2:

3 + 2 = I2R2 + I3R3

Label: 3 Is;+/- on Rs;loops.

Write equations.


Figure 26.66

5.00 A = I4

4.00I3 I2

A

BLabel the 3 branch currents I2, I3, and I4.

Since VAB across all 3 branches is the same and is known: V4 = I4R4 = 5A (4) = 20 Volts, the currents and can be readily solved.


V4 = I4R4 = 5A (4) = 20 VoltsI3 = V3 / R3 = 4V / 3 = 1.33 A

At junction B, I in = I outI4 = I2 + I3 ; I2 = I4 I3 = 5A - 1.3A

I2 = 3.7ALoop #1: V rises = V dropsLoop #1: V rises = V drops

= I2R2 + I4R4 = 3.7A (2) + 5A(4) = 27.4 V


5.0 A

4.00

B

I3 I2

V4 = I4R4 = 5A (4) = 20 VoltsI3 = V3 / R3 = 4V / 3 = 1.33 A

At junction B, I in = I outI4 = I2 + I3 ; I2 = I4 - I3 = 5A - 1.3A = 3.7A

Loop #1: V rises = V drops

= I2R2 +I4R4 = 3.7A (2) + 5A(4) =27.4 VDr.R.Anushya,SRREC,Padur

Series Resistors & Voltage Division

Series resistors same current flowing through them.

v1= iR1 & v2 = iR2

KVL:

v-v1-v2=0

v= i(R +R ) v= i(R1+R2)

i = v/(R1+R2 ) =v/Req

or v= i(R1+R2 ) =iReq

iReq = R1+R2


Series Resistors & Voltage Division

Voltage Division:

Previously:

v1 = iR1 & v2 = iR21

i = v/(R1+R2 )

Thus:

v1=vR1/(R1+R2)

v2=vR2/(R1+R2)Dr.R.Anushya,SRREC,Padur

Parallel Resistors & Current Division

Parallel resistors Common voltage across it.

v = i1R1 = i2R2

i = i1+ i2

= v/R1+ v/R2

= v(1/R1+1/R2)

=v/Req

v =iReq

1/Req = 1/R1+1/R2

Req = R1R2 / (R1+R2 )Dr.R.Anushya,SRREC,Padur

Parallel Resistors & Current Division

Current Division:

Previously:

v = i1R1 = i2R2

v=iReq = iR1R2 / (R1+R2 ) v=iReq = iR1R2 / (R1+R2 )

and i1 = v /R1 & i2 =v/ R2

Thus:

i1= iR2/(R1+R2)

i2= iR1/(R1+R2 )Dr.R.Anushya,SRREC,Padur

AC AND DC CIRCUITS


SINGLE PHASE AC CIRCUITS1. AmplitudeIt is the maximum value attained by an alternating quantity. Also

called as maximum or peak value

2. Time Period (T)It is the Time Taken in seconds to complete one cycle of an alternating

quantityquantity

3. Instantaneous Value

It is the value of the quantity at any instant

4. Frequency (f)

It is the number of cycles that occur in one second. The unit

for frequency is Hz or cycles/sec.


Advantages of AC system over DC systemAC voltages can be efficiently stepped up/down using transformer AC motors are cheaper and simpler in construction than DC motors Switchgear for AC system is simpler than DC system


Phasor RepresentationAn alternating quantity can be represented using

Waveform Equations PhasorPhasor


In Phase


Lagging


Leading


THREE PHASE AC CIRCUITS


MEASURING INSTRUMENTSThe device used for comparing the unknown quantity with

the unit of measurement or standard quantity is called a

Measuring Instrument.

OR

An instrument may be defined as a machine or system

which is designed to maintain functional relationship

between prescribed properties of physical variables &

could include means of communication to human

observer.


CLASSIFICATION OF INSTRUMENTSElectrical instruments may be divided into two categories, that

are;

1. Absolute instruments,

2. Secondary instruments.

- Absolute instruments gives the quantity to be measured in- Absolute instruments gives the quantity to be measured in

term of instrument constant & its deflection.

- In Secondary instruments the deflection gives the

magnitude of electrical quantity to be measured directly.

These instruments are required to be calibrated by

comparing with another standard instrument before

putting into use.


CLASSIFICATION OF INSTRUMENTSElectrical measuring instruments may also be classified according

to the kind of quantity, kind of current, principle of operation

of moving system.

CLASSIFICATION OF SECONDARY INSTRUMENTSCLASSIFICATION OF SECONDARY INSTRUMENTS

Secondary instruments can be classified into three

types;

i. Indicating instruments;

ii. Recording instruments;

iii. Integrating instruments.


CLASSIFICATION OF SECONDARY INSTRUMENTS

- Indicating Instruments:

It indicate the magnitude of an electrical

quantity at the time when it is being measured. The

indications are given by a pointer moving over a graduated

dial.dial.



- Recording Instruments:

The instruments which keep a

continuous record of the variations of the magnitude of an

electrical quantity to be observed over a defined period of

time.time.



- Integrating Instruments:

The instruments which measure the total

amount of either quantity of electricity or electrical energy

supplied over a period of time. For example energy meters.


ESSENTIALS OF INDICATING INSTRUMENTS

A defined above, indicating instruments are those which

indicate the value of quantity that is being measured at the

time at which it is measured. Such instruments consist

essentially of a pointer which moves over a calibrated scale

& which is attached to a moving system pivoted in bearing.& which is attached to a moving system pivoted in bearing.

The moving system is subjected to the following three

torques:

1. A deflecting ( or operating) torque;

2. A controlling ( or restoring) torque;

3. A damping torque.


DEFLECTING TORQUE

- The deflecting torque is produced by making one

of the magnetic, heating, chemical, electrostatic

and electromagnetic induction effect of current

or voltage and cause the moving system of theor voltage and cause the moving system of the

instrument to move from its zero position.

- The method of producing this torque depends

upon the type of instrument.


CONTROLLING TORQUE

- The magnitude of the moving system would be some what

indefinite under the influence of deflecting torque, unless

the controlling torque existed to oppose the deflecting

torque.

- It increases with increase in deflection of moving system.- It increases with increase in deflection of moving system.

- Under the influence of controlling torque the pointer will

return to its zero position on removing the source

producing the deflecting torque.

- Without controlling torque the pointer will swing at its

maximum position & will not return to zero after

removing the source.


- Controlling torque is produced either by spring or gravity control.

Spring Control:

When the pointer is deflected

one spring unwinds itself while

the other is twisted. This twist in

the spring produces restoring

(controlling) torque, which is

proportional to the angle of

deflection of the moving systems.


Spring Control


Gravity Control

In gravity controlled instruments, a small adjustable

weight is attached to the spindle of the moving system

such that the deflecting torque produced by the

instrument has to act against the action of gravity.

Thus a controlling torque is obtained. This weight is called

the control weight. Another adjustable weight is also

attached is the moving system for zero adjustment andattached is the moving system for zero adjustment and

balancing purpose. This weight is called Balance weight.


DAMPING TORQUE

We have already seen that the moving system of the

instrument will tend to move under the action of the

deflecting torque.

But on account of the control torque, it will try to occupy

a position of rest when the two torques are equal and

opposite.opposite.

However, due to inertia of the moving system, the pointer

will not come to rest immediately but oscillate about its

final deflected position as shown in figure and takes

appreciable time to come to steady state.

To overcome this difficulty a damping torque is to be

developed by using a damping device attached to the

moving system. Dr.R.Anushya,SRREC,Padur

DAMPING TORQUE

The damping torque is proportional to the speed of rotation

of the moving system, that is

Depending upon the degree of damping introduced in the

moving system, the instrument may have any one of the

following conditions as depicted in above graph.


DAMPING TORQUE

1. Under damped condition:

The response is oscillatory

2. Over damped condition:

The response is sluggish and it rises very slowly from its zero

position to final position.

3. Critically damped condition:

When the response settles quickly without any oscillation, theWhen the response settles quickly without any oscillation, the

system is said to be critically damped.


The damping torque is produced by the

following methods:

1.Air Friction Damping

2.Fluid Friction Damping

3.Eddy Current Damping

4.Electromagnetic

Damping


PMMC

Principle of Operation: When a current carrying conductor is placed in a magnetic field, it experiences a force and tends to move in the direction as per Flemings left hand rule.

Fleming left hand rule: If the first and the second finger and the thumb of the left hand are held so that they are at right the thumb of the left hand are held so that they are at right angle to each other, then the thumb shows the direction of the force on the conductor, the first finger points towards the direction of the magnetic field and the second finger shows the direction of the current in the wire.


Construction:

A coil of thin wire is mounted on an aluminum frame (spindle) positioned between the poles of a U shaped permanent magnet which is made up of magnetic alloys like alnico.

The coil is pivoted on the jewelled bearing and thus the coil is free to rotate. The current is fed to the coil through spiral springs which are two in numbers. The coil which carries a current, which is to be measured, moves in a spiral springs which are two in numbers. The coil which carries a current, which is to be measured, moves in a strong magnetic field produced by a permanent magnet and a pointer is attached to the spindle which shows the measured value.


PMMC instruments internal structure


Working:

When a current flow through the coil, it generates a magnetic field which is proportional to the current in case of an ammeter. The deflecting torque is produced by the electromagnetic action of the current in the coil and the magnetic field.

The controlling torque is provided by two phosphorous bronze flat coiled helical springs. These springs serve as a bronze flat coiled helical springs. These springs serve as a flexible connection to the coil conductors.

Damping is caused by the eddy current set up in the aluminum coil which prevents the oscillation of the coil.


Torque Equation


Advantages:

The PMMC consumes less power and has great accuracy.

It has uniformly divided scale and can cover arc of 270

degree.

The PMMC has a high torque to weight ratio.

It can be modified as ammeter or voltmeter with

suitable resistance.suitable resistance.

It has efficient damping characteristics and is not

affected by stray magnetic field.

It produces no losses due to hysteresis.


Disadvantage:

The moving coil instrument can only be used on D.C

supply as the reversal of current produces reversal of

torque on the coil.

Its very delicate and sometimes uses ac circuit with a

rectifier.

Its costly as compared to moving coil iron instruments. Its costly as compared to moving coil iron instruments.

It may show error due to loss of magnetism of

permanent magnet.


Moving Iron Instruments Voltmeter and

Ammeter

Construction and basic principle operation of moving-iron instruments

Moving-iron instruments are generally used to measure alternating voltages and currents. In moving-iron instruments the movable system consists of one or more pieces of specially-shaped soft iron, which are so pivoted as pieces of specially-shaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil.

There are two general types of moving-iron instruments namely:

1. Repulsion (or double iron) type2. Attraction (or single-iron) type


Moving-iron instrument

An attraction type of moving-iron instrument is showndiagrammatically in Figure. When current flows in thesolenoid, a pivoted soft-iron disc is attracted towardsthe solenoid and the movement causes a pointer tomove across a scale.

In the repulsion type moving-iron instrument shown In the repulsion type moving-iron instrument showndiagrammatically in Figure, two pieces of iron are placedinside the solenoid, one being fixed, and the otherattached to the spindle carrying the pointer.


The brief description of different components of

a moving-iron instrument is given below:

Moving element: a small piece of soft iron in the form of a vane or rod.

Coil: to produce the magnetic field due to current flowing through it and also to magnetize the iron pieces.

In repulsion type, a fixed vane or rod is also used and magnetized with the same polarity.magnetized with the same polarity.

Control torque is provided by spring or weight (gravity).

Damping torque is normally pneumatic, the damping device consisting of an air chamber and a moving vane attached to the instrument spindle.

Deflecting torque produces a movement on an aluminum pointer over a graduated scale.


Repulsion type:


Attraction type:


Working:

The deflecting torque in any moving-iron instrument is due

to forces on a small piece of magnetically soft iron that is

magnetized by a coil carrying the operating current. In

repulsion type movingiron instrument consists of two

cylindrical soft iron vanes mounted within a fixed current-

carrying coil. One iron vane is held fixed to the coil frame

and other is free to rotate, carrying with it the pointer shaft. and other is free to rotate, carrying with it the pointer shaft.

Two irons lie in the magnetic field produced by the coil that

consists of only few turns if the instrument is an ammeter

or of many turns if the instrument is a voltmeter.


Working:

Current in the coil induces both vanes to become

magnetized and repulsion between the similarly

magnetized vanes produces a proportional rotation. The

deflecting torque is proportional to the square of the

current in the coil, making the instrument reading is a true

RMS quantity Rotation is opposed by a hairspring that

produces the restoring torque. Only the fixed coil carries produces the restoring torque. Only the fixed coil carries

load current, and it is constructed so as to withstand high

transient current.

Moving iron instruments having scales that are nonlinear

and somewhat crowded in the lower range of calibration


Advantages:

The instruments are suitable for use in AC and DC

circuits.

The instruments are robust, owing to the simple

construction of the moving parts.

The stationary parts of the instruments are also simple.

Instrument is low cost compared to moving coil Instrument is low cost compared to moving coil

instrument.

Torque/weight ratio is high, thus less frictional error.


Moving-iron instrument


Construction of PMMC Instruments

The constructional features of this instrument are shown in Fig.

The moving coil is wound with many turns of enameled or silk

covered copper wire.

The coil is mounted on rectangular aluminum former, which is

pivoted on jeweled bearings.

The coils move freely in the field of a permanent magnet. The coils move freely in the field of a permanent magnet.

Most voltmeter coils are wound on metal frames to provide

the required electro-magnetic damping.

Most ammeter coils, however, are wound on non-magnetic

formers, because coil turns are effectively shorted by the

ammeter shunt.

The coil itself, therefore, provides electro magnetic damping.


PARTS:


PERMANENT MAGNET

RECTANGULAR COIL

CONTROLLED SPRINGS

ALLUMINIUM CYLINDRICAL CORE

POINTER

PIVOTS PIVOTS

SCALE

DUST PROOF CASE


MAGNET SYSTEMS

Old style magnet system consisted of relatively long U

shaped permanent magnets having soft iron pole

pieces.

Owing to development of materials like Alcomax and

Alnico, which have a high co-ercive force, it is possible

to use smaller magnet lengths and high field to use smaller magnet lengths and high field

intensities.

The flux densities used in PMIMC instruments vary

from 0.1 Wb/m to 1 Wb/m.


CONTROL

When the coil is supported between two jewel

bearings two phosphor bronze hairsprings provide

the control torque.

These springs also serve to lead current in and out

of the coil. The control torque is provided by the of the coil. The control torque is provided by the

ribbon suspension as shown.

This method is comparatively new and is claimed to

be advantageous as it eliminates bearing friction.


RECTANGULAR IN SHAPE

WOUND ON ALUMINIUM

FORMER WITH LARGE NO.OF

TURNS.

WIDTH OF RECTANGLE IS

DEFLECTING COILS

WIDTH OF RECTANGLE IS

LESS THAN DISTANCE b/w

POLES OF PM WITH AN AIR

GAP.


A LIGHT ALUMINIUM

CYLINDER WITH

PIVOT AT TOP AND

BOTTOM IS MADE

ALUMINIUM CORE

BOTTOM IS MADE

TO FIT OVER THE

AXLE OF MOVING

COIL AND ACTS AS

DAMPING

MECHANISMS.


POINTER AND SCALE:


The pointer is carried by the spindle and moves

over a graduated scale.

The pointer is of lightweight construction and,

apart from those used in some inexpensive

instruments has the section over the scale twisted

to form a fine blade.

This helps to reduce parallax errors in the reading This helps to reduce parallax errors in the reading

of the scale. When the coil is supported between

two jewel bearings two phosphor bronze

hairsprings provide the control torque.

These springs also serve to lead current in and out

of the coil.


THE WHOLE

INSTRUMENT IS

ENCLOSED IN A DUST

PROOF CASE

DUST PROOF CASE

PROOF CASE

THE SHAPE AND SIZE

OF THE CASE

DEPENDS UPON THE

CAPACITY OF THE

INSTRUMENT


IT WORKS ON THE

PRINCIPLE OF DC

MOTOR

WHEN CURRENT

WORKING

WHEN CURRENT

PASSES THROUGH

THE COIL,IT

PRODUCES FLUX OF

THE CORE


THE FLUX DENSITY AT ONE SIDE INCREASES

WHILE OTHER SIDE DECREASES

THIS IMBALANCE EXERTS A FORCE ON THE

CONDUCTOR IN THE DIRECTION OF LEAST

WORKING

CONDUCTOR IN THE DIRECTION OF LEAST

FLUX DENSITY


TORQUE

>Torque, moment or moment of force is the tendency of a force to rotate an object about an axis, fulcrum, or pivot.

>DEFLECTING TORQUE=TOTAL FORCE*DISTANCE

=>Td=NABI

N=NO.OF TURNSN=NO.OF TURNS

B=FLUX DENSITY

A=AREA OF CROSS SECTION

I=CURRENT

>AT FINAL DEFLECTION Td=Tc

=>Tc PROPORTIONAL TO I

HERE DAMPING IS EDDY CURRENT DAMPINGDr.R.Anushya,SRREC,Padur

- The PMMC consumes less power and has great

accuracy.

- It has uniformly divided scale and can cover arc of

270 degree.

- The PMMC has a high torque to weight ratio.

ADVANTAGES:

- The PMMC has a high torque to weight ratio.

- It can be modified as ammeter or voltmeter with

suitable resistance.

- It has efficient damping characteristics and is not

affected by stray magnetic field.

- It produces no losses due to hysteresis.Dr.R.Anushya,SRREC,Padur

-The moving coil instrument can only be used on D.C supply as the reversal of current produces reversal of torque on the coil.

- Its very delicate and sometimes uses ac circuit with a rectifier.

DISADVANTAGES:

with a rectifier.

- Its costly as compared to moving coil iron instruments.

- It may show error due to loss of magnetism of permanent magnet.

You may also read Minimize the risk of electrical shock on ship.


DYNAMOMETER

This instrument is suitable for the measurement of direct and

alternating current, voltage and power.

The deflecting torque in dynamometer is relies by the

interaction of magnetic field produced by a pair of fixed air

cored coils and a third air cored coil capable of angular

movement and suspended within the fixed coil.movement and suspended within the fixed coil.


Single Phase induction type energy meter :


Construction:

Driving System

Moving System Moving System

Breaking System

Registering system


Driving system:

consist of two electromagnets : one formed by

current coil & other by voltage coil or pressure coil.

It develops torque to rotate the moving system

Shading bands are bound to make angle b/w the

flux and applied voltage equal to 90 degree

Moving system:Moving system:

consists of an aluminum disk mounted on the

spindle which is supported by Pivot-jewel Bearing

system.

Rotation of this disk is base of energy measurement


Breaking system:

Consists of a permanent magnet of c shaped

covering a part of rotating disk to provide

breaking torquebreaking torque

this torque is opposite to driving torque.

Registering system: displays the amount of energy


Working:

When the energy meter is connected in the circuit,

the current coil carries the load current and the

pressure coil carries the current proportional to the

supply voltage.

The magnetic field produced by the SERIES magnet The magnetic field produced by the SERIES magnet

(series coil) is in phase with the line current & the

magnetic field produced by the shunt magnet

(pressure coil) is in quadrature with the applied

voltage (since the coil is highly inductive).


Thus, a phase difference exists between the fluxes

produced by the two coils. This sets up a rotating

field which interacts with the eddy current

produced in the disc(because of induced emf) and

produces a driving torque and, thus, disc starts

rotating.

The number of revolutions made by the disc

depends upon the energy passing through the

meter. The spindle is geared to the recording

mechanism so that electrical energy consumed in

the circuit is directly registered in KWh.Dr.R.Anushya,SRREC,Padur

The speed of the disc is adjusted by

adjusting the position of the breaking

magnet.

For example, if the energy meter registers

less energy than the energy actually

Working:

less energy than the energy actually

consumed in the circuit, then the speed of

disc has to be increased which is obtained by

shifting the magnet nearer to the centre of

the Disc and vice-versa.


Advantages: The induction type energy meter have high

accuracy.

They are simple and robust in construction.

They require minimum maintenance.

They are cheap in cost.

Their range can be increased by using instrument

transformer.


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UNIT-1