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Topic Title: one fuse two motors
Topic Summary: is this right? I may have posted this in the wrong place
Created On: 25 June 2013 04:26 PM
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 25 June 2013 04:26 PM
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poni

Posts: 4
Joined: 12 December 2008


we have one set (3 phase)of 160A fuses
with cables(2X3) going into 2X DOL contactors one for each motor, then out to two 22Kw motors
the cables are 4core 16mm2 SWA and the OL is set at 40a
as the cable will only carry 100A max is this OK
I have tried to load the wiring dig for this but unable to attach it
 27 June 2013 01:44 PM
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ipjones

Posts: 2
Joined: 18 January 2003

Not really good practice - cables are a larger than I would spec, but without knowing lengths and load details, cannot comment.
Each motor should ideally have it's own MCB which will give short circuit and overload protection. your contactors must be rated for 160A backup fuse i.e. typiclly 65A
 05 August 2013 10:25 PM
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poni

Posts: 4
Joined: 12 December 2008

thanks for the reply yes the cable run is long over 100m, that was not the problem, it was the fuse size to cable ,
yes the contactors will carry the current , but the cable will not on a short-circuit , my question, is it OK to rely on the overload for short-circuit protection?
 07 August 2013 10:47 PM
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Avatar for Legh.
Legh

Posts: 3488
Joined: 17 December 2004

I'm surprised that nobody from the dark side hasn't picked up on this one....or maybe they have ! ?

S/C separately for each cct seems Ok but not spontaneous S/C's.
and
What about earth faults as the SWA will be the only E/F protection?.

The 100A max is for start up currents, so the motors are not going to be started simultaneously ?

I personally would protect each motor separately with something along the lines of a C40A but others might have reservations.

Legh

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 25 October 2013 01:33 PM
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ysohail78

Posts: 7
Joined: 01 June 2012

its better to protect each motor, better to attached the single line drawing for better understanding....
Younus
 26 November 2013 10:17 AM
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edwinjarvis

Posts: 11
Joined: 13 November 2013

better to protect motor.....
 26 November 2013 02:59 PM
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Pactrol

Posts: 860
Joined: 22 February 2004

Hi seems the motors are protected by overloads so its fault current for the cable feeding the starters that needs checking against disconnection time
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