motor starter types and technology and its applications

7/24/2019 Motor Starter Types and Technology And Its Applications

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Types And

Technology ofMotor Starter And

Applications



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Types And Technology ofMotor Starter And

ApplicationsIntroduction:

An induction motor is a 3 phase motor consisting of the 3phase winding as the stator with a permanent magnetand the rotor as another 3 phase windings. It works onthe principle of rotating magnetic eld, i.e. the formationof the magnetic ux from 3 phase winding uxes, whichrotates about its axis, causing the rotor to rotate.





ApplicationsBlock Diagram





ApplicationsNeed for MotorStarting

In an induction motor, when suppl! is gi"en to the statorwindings.

#he rotating magnetic eld ux and the produced ux inthe rotor windings due to the back emf.

It causes the motor tor$ue to increase, causing a high

rotor current.

%uring the time between the application of electric suppl!to the motor and the actual acceleration of the motor to itsfull speed.

A large amount of current is drawn b! the stator from the





Applicationseed for Motor Starting

#his starting current is about & to ' times more than thefull load current.

#his time duration can be for few seconds or longer.

#his causes the electrical e$uipments to damagebecause of the increasing "oltage drop in electricals!stems.

%ue to ow of larger currents across the cable.

(or this reason, a denite method of starting the motoris needed.





ApplicationsDenition of MotorStarter

It is the de"ice connected in series with the motor todecrease its starting current and then increase it as the

motor starts rotating graduall!.

It consists of a connector which acts as a switch tocontrol ow of current to the motor and a o"erload unitwhich measures the ow of current through the motor

and controls the halting of motor in case of large currentbeing drawn.


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ApplicationsPrinciple of MotorStarter

#he current drawn b! the motor can be controlled b!reducing the back emf )possible b! reducing the suppl!"oltage* or b! increasing the rotor resistance during themotor starting.




ApplicationsTypes of MotorStarters

Direct n line

Star Delta Auto Transformer starter

Stator !esistance Starter

!otor !esistance Starter




ApplicationsDirect n line

It consists of simple push button as the controller.

+hen the start button is pressed.

#he switch connecting the motor and the main suppl!is closed and the motor gets the suppl! current.

In case of o"er current, the stop button is pressed and

the b!pass auxiliar! contact is opened.




ApplicationsDirect n line




ApplicationsStarDelta

#he 3 windings are rst connected in star connection.

After some time )decided b! the timer or other controllercircuit* the windings are connected in delta connection.

In star connection, the current drawn is .&- of thenormal current and also the phase "oltage is reduced to.&-.

#hus the tor$ue is reduced.




ApplicationsStar Delta




ApplicationsAuto Transformerstarter

It consists of an auto transformer in star connection.

It reduces the "oltage applied to the motor terminals.

It consists of 3 tapped secondar! coils connected to thethree phases.

In the starting period the transformer allows applicationof lower "oltages to the three windings.




ApplicationsAuto Transformer starter




ApplicationsStator !esistanceStarter It consists of three resistors in series with each phase of the

stator windings.

It causes a "oltage drop across each resistor and as a result alow "oltage is applied to each phase.




Applications!otor !esistanceStarter It consists of 3 resistances connected in series with the

rotor windings, thus reducing the rotor current, butincreasing the tor$ue.




ApplicationsApplication of Star Delta Starter to "ontrolStarting of Induction Motor





#he star delta starter is the cheapest among all the startersand is suitable for applications like machine tools, pumps,

motor generators etc.

A star delta starter can be used in starting an inductionmotor b! using rela!s as the connector and the timer asthe controller.

0 connector is used to pro"ide the mains suppl! while theother connector controls the connection of motor in star ordelta connection.

#ransformers are used, primaries of which are connected tothe 3 phase suppl! and the secondaries are connected to





#he two rela!s are used to trigger the timer, which

de"elops a high logic output at pin 3.

#hus switching on the rela! 1, causing the suppl! in starconnection

It o2ers low power intensit! to the load b! isolating theload from the normal 3 phase suppl! through rela! 3.

ome more regarding this starting of induction discussedbelow.




ApplicationsSoft Start of Induction Motor #y Stepped Delay of!educing $iring Angle

Soft Start and SoftStop In normal start up of the induction motor, more tor$ue

is de"eloped.

It causes the stress to be transferred to the mechanicaltransmission s!stem.

It results in excessi"e wear and failure of themechanical parts.

As acceleration increases, high current is drawn whichis about ' of the normal run current.

#his can be seldom sol"ed usin a star delta starter

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ApplicationsSoft Start and SoftStop

oft start pro"ides a reliable and economical

solution to these problems b! deli"ering acontrolled release of power to the motor,thereb! pro"iding smooth, steeples accelerationand deceleration. #he damage to windings andbearings are reduced, resulting in an extendedmotor life.





Applicationsoft Start and Soft Stop +ith this techni$ue, a controlled starting and stopping is

achie"ed with proper selection of ramp times and setting ofthe current limit.

4ess mechanical stress.

Impro"ed power factor.

4ower maximum demand.

4ess mechanical maintenance.

#his techni$ue is suitable for applications where tor$uetransients are fre$uent, such as in pumping uids, which can

ultimatel! lead to rupture pipes and couplings.





ApplicationsTechnology follo%ed in SoftStarter: A soft starter is a t!pe of reduced "oltage starter for A5

induction motors.

#he soft starter is similar to a primar! resistance orprimar! reactant starter in that it is in series with thesuppl! to the motor.

#he input current to the started e$uals its output current.

It consists of solid state de"ices to control the current owand the "oltage applied to the motors.

#he soft starters can be connected in series with the line"oltage or connected inside the delta loop.





Applications&oltage "ontrol

olid state A5 switches are arranged in series with one ormore phases to achie"e "oltage control.

'se of Solid states%itches

0 x #riac per phase





Applicationsse of Solid state s%itches

0 x 56 and 0 x %iode re"erse parallel connectedper phase.

x 56s re"erse parallel connected per phase.

T A d T h l f





ApplicationsAd(antages

tar7%elta starters are widel! used due to theirrelati"el! low price.

#here are no limits to the number of times the!can be operated.

#he components re$uire "er! little space.

#he starting current is reduced to approximatel!one7third.

T A d T h l f





ApplicationsDisad(antages

#he starter can onl! be applied to motors where the sixleads or terminals can be accessed.

#he suppl! "oltage must be the same as the ratedmotor "oltage for %elta connection.

8ecause the starting current is reduced toapproximatel! one7third of the rated current, the

starting tor$ue is also reduced to one7third.

If the motor does not reach at least 9 of its ratedspeed at the time of switching from tar to %elta thecurrent peak will be as high as in a %..4.

T A d T h l f





Applications"onclusion

;ost induction motors are started directl! on line, butwhen "er! large motors are started that wa!, the!

cause a disturbance of "oltage on the suppl! lines dueto large starting current surges. #o limit the startingcurrent surge, large induction motors are started atreduced "oltage and then ha"e full suppl! "oltagereconnected when the! run up to near rotated speed.

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