Overview of Electrical machines

7/23/2019 Overview of Electrical machines

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ELECTRICALELECTRICALMACHINESMACHINES


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TYPES OF MOTORSTYPES OF MOTORS

universal

cumulative

diferentialcompound

shunt

series

DC

synchronous

wound rotor

squirrel cagethreephase

shaded pole

repulsion motor

permanent-split

capacitor

two-value

capacitorcapacitor-type

split-phase

induction

single

phaseAC


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DC MOTORSDC MOTORS


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Series MotorSeries Motor

High Starting TorqueHigh Starting Torque

Speed varies with loadSpeed varies with load

Will run away with no loadWill run away with no load

Used for applications where theUsed for applications where the

load is always connectedload is always connected


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Use:Use:

For work that demands high startingFor work that demands high starting

torque such as locomotives, cranes,torque such as locomotives, cranes,hoists, street cars, automobile starters.hoists, street cars, automobile starters.


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Shunt MotorShunt Motor

Average Starting TorqueAverage Starting Torque

Speed is fairly constantSpeed is fairly constant

Self-regulatingSelf-regulating

Will run away if field is openedWill run away if field is opened

Used in the industry whereUsed in the industry wherereasonably constant speed isreasonably constant speed is

importantimportant


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Use:Use:Blowers, fans, etc.Blowers, fans, etc.


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Cumulative Compound MotorCumulative Compound Motor

Excellent Starting TorqueExcellent Starting Torque

Better constant speed than Shunt motorBetter constant speed than Shunt motor

Will not run away under no-loadWill not run away under no-loadUsed for high starting torque and for noUsed for high starting torque and for no

run away conditionsrun away conditions

Use:Use:Heavy duty starting such as elevators,Heavy duty starting such as elevators,

escalatorsescalators


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Differential Compound MotorDifferential Compound Motor

Very Poor Starting TorqueVery Poor Starting Torque

Constant speedConstant speed


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AC MOTORSAC MOTORS


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SINGLE PHASESINGLE PHASEMOTORSMOTORS


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1. SPLIT-PHASE MOTOR1. SPLIT-PHASE MOTORThe most popular type of singleThe most popular type of singlephase motor.phase motor.

Sizes:Sizes:

Used wherever motors of 1/20 1/3 HpUsed wherever motors of 1/20 1/3 Hpare required.are required.

Types of Motors


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Use:Use:

General purpose, high torque, fullGeneral purpose, high torque, full

voltage start fans, blowers, pumps,voltage start fans, blowers, pumps,

power tools, etc.power tools, etc.

Types of Motors


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2. CAPACITOR-TYPE MOTOR2. CAPACITOR-TYPE MOTOR

It can be made by connecting aIt can be made by connecting a

capacitor in the motor circuit at thecapacitor in the motor circuit at the

proper point in series with startproper point in series with start

winding.winding.

Sizes:Sizes:Generally 1/20 10 HpGenerally 1/20 10 Hp

Types of Motors


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Use:Use:High starting torque, high pf,High starting torque, high pf,

quiet operationquiet operation

refrigerators, air conditioners,refrigerators, air conditioners,

hoistshoistsTypes of Motors


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Two types of Capacitor-typeTwo types of Capacitor-type

motor:motor:

1. Two value capacitor motor1. Two value capacitor motor

- greater starting torque- greater starting torque

2. Permanent-split capacitor motor2. Permanent-split capacitor motor

- low starting torque- low starting torque

Types of Motors


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3. REPULSION MOTOR3. REPULSION MOTOR

Often called anOften called aninductive seriesinductive seriesmotormotor

Its speed & torque characteristics areIts speed & torque characteristics are

similar to that of a DC series motor.similar to that of a DC series motor.

Size:Size:Generally 1/8 5 HpGenerally 1/8 5 Hp

Types of Motors


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Use:Use:Constant speed motor, across theConstant speed motor, across the

line startingline startingVacuum cleaner, floor polisher, etc.Vacuum cleaner, floor polisher, etc.

Types of Motors


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4. SHADED POLE MOTORS4. SHADED POLE MOTORS

Known for itsKnown for itssimplicity andsimplicity andlong lifelong life

Low startingLow startingtorquetorque

Sizes:Sizes:GenerallyGenerally1/250 1/40 Hp1/250 1/40 Hp

Use:Use:Driving smallDriving small

fans, clocksfans, clocks Types of Motors


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THREE PHASETHREE PHASE

MOTORSMOTORS


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1. INDUCTION MOTOR1. INDUCTION MOTOR

The most common type of AC motorThe most common type of AC motor

A. SQUIRREL CAGEA. SQUIRREL CAGE- comparatively low in cost per- comparatively low in cost per

horsepowerhorsepower

- good starting torque and overload- good starting torque and overloadcapacity are highly efficientcapacity are highly efficient

- constant speed motors- constant speed motors

Types of Motors


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Uses:Uses:fans, blowers, compressors, pumpsfans, blowers, compressors, pumps

Types of Motors


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B. WOUND ROTOR MOTORB. WOUND ROTOR MOTOR

--High starting torqueHigh starting torque

- Low starting current- Low starting current

- Variable speed- Variable speed

- Always operated on a three-- Always operated on a three-

phase system & generallyphase system & generally

connected wyeconnected wye

- Sometimes referred to as the- Sometimes referred to as the

slip ring motorslip ring motor

Types of Motors


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Use:Use:Fans, centrifugalFans, centrifugal

and plungerand plunger

pumps,pumps,compressors,compressors,

conveyors,conveyors,

hoists andhoists and

cranes, etc.cranes, etc.

Types of Motors


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Advantages of Wound RotorAdvantages of Wound Rotorover the Squirrel Cage Typeover the Squirrel Cage Type

1)1)It will develop high starting andIt will develop high starting and

accelerating torque.accelerating torque.2)2)With the rotor resistance set to getWith the rotor resistance set to get

maximum starting torque, it drawsmaximum starting torque, it draws

less starting current.less starting current.3)3)It offers the possibility of virtuallyIt offers the possibility of virtually

step less speed control.step less speed control.


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DisadvantagesDisadvantagesof Wound Rotorof Wound Rotorover the Squirrel Cage Typeover the Squirrel Cage Type

1)1)The efficiency is almost directlyThe efficiency is almost directlyproportional to the operating speed. Atproportional to the operating speed. At50% of synchronous speed, efficiency is50% of synchronous speed, efficiency is

virtually cut in half, and this becomesvirtually cut in half, and this becomesimportant if the motor runs at low speedimportant if the motor runs at low speedfor long periods.for long periods.

2)2)The controllers does not change the no-The controllers does not change the no-

load speed very much, and so at lowload speed very much, and so at lowspeed settings the speed regulationspeed settings the speed regulationbecomes very poor.becomes very poor.

3)3)They cost much more than squirrel cageThey cost much more than squirrel cagemotor.motor.


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2. SYNCHRONOUS MOTOR2. SYNCHRONOUS MOTOR

Runs at a speed exactlyRuns at a speed exactlyproportionalproportional to theto thefrequency of the supplyfrequency of the supply

current.current.Constant speedConstant speed

Very little starting torqueVery little starting torque

No overload capacity andNo overload capacity and

are quite inefficientare quite inefficient

Use:Use:Timing devices such asTiming devices such aselectric clockselectric clocks

Types of Motors


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UNIVERSAL MOTORUNIVERSAL MOTOR

Quite similar to a series-wound DC motorQuite similar to a series-wound DC motor

Designed to run on DC or AC of the sameDesigned to run on DC or AC of the samevoltage and frequencyvoltage and frequency

Often called asOften called asAC series motorAC series motor

Sizes:Sizes:Generally 1/200 1/3 HpGenerally 1/200 1/3 Hp

Types of Motors


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Use:Use:

Vacuum cleaner,Vacuum cleaner,electric drills,electric drills,

sewing machine,sewing machine,

portable toolsportable tools

Types of Motors


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THANK !"#

Overview of Electrical machines

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