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 Post subject: Short Circuit Study - Motor Contribution
PostPosted: Tue May 10, 2022 3:05 am 

Joined: Thu Jun 09, 2016 6:17 pm
Posts: 8
Hello,

When developing a model in order to run short circuit analyses, is it recommended to group LV motors <50HP? Upon looking at IEEE 399 and IEEE 551, this appears to be typical. Are individuals utilizing this technique or modeling all LV motors individually?

Thanks for the input.


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 Post subject: Re: Short Circuit Study - Motor Contribution
PostPosted: Tue May 10, 2022 6:23 am 
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Joined: Thu Apr 18, 2019 11:42 am
Posts: 84
I would use the red book as your go-to source, along w/ the purple/violet book. Per the red book, small motors are lumped into one "motor source" from a modelling perspective.

Mike


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 Post subject: Re: Short Circuit Study - Motor Contribution
PostPosted: Tue Jul 12, 2022 1:03 pm 

Joined: Thu Apr 21, 2022 1:00 am
Posts: 1
Location: Scotland, UK
Hello, I'm in the UK where we typically run short circuit studies in accordance with IEC 60909. That standard suggests that "for simplification of the calculation" groups of asynchronous low-voltage motors "may be combined to a single equivalent motor". We generally follow this advice with our modelling and combine LV motors at each switchboard or MCC.

However, if there is a particularly large LV motor that may dominate a scenario (for example, an electric driven fire pump that is online when the system is in emergency mode) then we do model that as a standalone motor so we can switch it in/out as necessary.

Combining LV motors also reduces the task of data collection! We typically only ask for detailed motor data for the largest LV motors - this is in case we need to add them for a particular scenario, or for use in other studies such as coordination.

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Nick Bramhall, CEng
safearc.co.uk


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