Selecting Electrical Contactors

Depends on how large the motors are?

For conveyor applications, a standard IEC contactor and overload from Siemens, Telemecanique, AB will all do a fine job and are relatively inexpensive.

For larger motors I recommend a NEMA Starter.

Thank you. our motor are not more than 10Kw, my concern is not for rating of motor,i am looking for a contactor that is suitable for frequent On-Off.because there is different duty cycle contactor are avilable ,But i want to know what type of contactor i can use for freuquent On- off motor.Please tell me clearly.

How about contacting (no pun intended) some manufacturers of <...Electrical contactors...> directly? Telephone?

Depending on the conveyor size and application, you should perhaps look into installing variable speed drives instead of contactors. Although more expensive, the enhanced starting torque and variable acceleration and deceleration available with the variable speed drive may be of benefit to you.

we already using AC-3 duty cycle contactor for all conveyor motor,but the contactor getting spoiled due to frequent on-off.I dont want spent more money for buying VFD drive.Please give me clear details about contactor for my usage.

Dear Paramasivam,

AT the outset AC contactors used for AC motors switching on/off control are selected on the basis of duty to be performed by these contactors.

These AC contactors come under different utilisation category

Category Application

AC-1 used for resistance load,non inductive or slightly inductive loads

AC-2 used for Slip ring motors starting/switching off

AC-3 Squirrel Cage motor startand switching off during running

AC-4 Squirrel cage motor starting,plugging and inching-Your requirement fits in this category.You should select AC-4 category of Ac contactor for frequent start and stop application.

It goes upto AC-8 for various applications.Similar Categorisation viz DC-1.DC-3,DC-5,DC-6 exists for DC motor switch on or off DC contactors

The above classification is as per IEC and IS-13947 standards.This can be referred for further details

Trust this is clear to you

V.Ambarani

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Thank you MR. Ambarani for your valuable suggestion.

I tnink u are inching the motors.Normally this is done after a power interuption to restart with load.The starting current will be flowing for a longer duration.Try using AC4 duty contactors.Vfd's in this won't be of much help either.

I want to know more details about AC-3 & AC-4.can you give me details about that.If we use higher rating AC-3 contactor insteed of using AC-4 , what is the different?

Kindly refer to the catalogues of Siemens India aor L&T catalogues where all details of contacors are given.Its actually a deration of higher rating for a lower rating for a severe duty.Hope u will have no difficulty in getting the catalogues.

Mr Prama...

Its of my opinion to use contactor suitable for AC23 duty motor. However, see motor data sheet, consult with manufacturer, then go for the contactor selection. Its very important to know your load first.

Best of luck.

Thanks

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