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Short circuit rating calculations

Posted By: Clyde

Short circuit rating calculations - 08/06/05 02:06 AM

I've recently run into a situation that I havn't thought about since my days as an apprentice.

I need to calculate the short circuit rating of a couple of machines that are not currantly approved for use in Canada. As part of the certification, they need to be labelled with voltage, FLA, hz, phase etc as well as short circuit ampacity.

These nachines have an electric motor, 120 volts, and some mechanics for a printing shop.

Can anyone tell me if there is a calculation available to complete this job.

Any help would be appreciated.
Posted By: bigrockk

Re: Short circuit rating calculations - 08/06/05 05:06 PM

I did a google search on " short circuit current rating approved method " and received alot of good results.

If this doesn't work out for you let me know and i will post some links, good luck.
Posted By: Ron

Re: Short circuit rating calculations - 08/06/05 09:04 PM

To label equipment with a short circuit rating, would be very dependent on the devices in the power path and how they were supported and manufactured. Then they would be tested at that rated current to ensure no catastrophic failure.
Posted By: Clyde

Re: Short circuit rating calculations - 08/12/05 02:28 AM

Thanks guys.

I agree with you Ron. There does not seem to be an effective way of testing the motors without actually destroying them in the process.

I did do a google search and found detailed methods of rating transformers but no motors.

I talked to the ESA field inspector and he indicated that for small motors (3/4 hp and smaller) a 5 ka is generally accepted.

Thanks for your thoughts. Any more would be appreciated.
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