Will 2 out of 3 Phases Trip a 3 Phase Breaker?

[Peter-L]

Hello,

We've had an issue with a 3 phase piece of equipment that was tripping the 3 phase breaker as soon as it was turned on. On investigation (by a certified electrician) he said it was the equipment at fault. I raised a return of the equipment and the new one arrived today. To be able to return the 'faulty' equipment I had to remove the commando socket from it and its associated cabling from the faulty one, on removing the access panel I found that the cable going into the phase 1 junction block was loose.

Would this loose cable have cause the breaker to trip, and if so would this have saved the hardware from being damaged when only receiving 2 out of 3 phases?

Any guidance much appreciated folks!

 

[Peter-L]

Thanks darkwood, I think the best thing for me to do is ensure the cables are tight and re-test to see if it still trips the breaker. Then potentially switch the tail to the new unit and perform the same test. This way I can be sure where the problem lies.

 

[markythesparky]

Surely you will need to replace the cable and MCB before you install the replacement UPS? Youve mentioned that the MCB is not the correct size!

 

[Peter-L]

Surely you will need to replace the cable and MCB before you install the replacement UPS? Youve mentioned that the MCB is not the correct size!

Hi, I thought as long as the breaker is the same or lower than the cable/UPS are rated too it would be better than the other way around?


The cables are -


"Titanex 11 HAR H07RN-F 5G6" which I believe to be -
5 Core with Green 6mm Core (50A)
http://www.nexans.com/eservice/Midd...5023/H07RN_F_TITANEX_industrial_flexible_.pdf


"Nexans BS 5467 H 4x10 2007 BASEC" which I believe to be -
http://www.nexans.co.uk/eservice/UK...XLPE_PVC_SWA_PVC_0_6_1_0_kV_2_4_conductor.pdf

 

[Pete999]

Oh yes loose connection high resistance high current

 

[Knobhead]

Oh yes loose connection high resistance high current

Would you care to clarify please?

 

[Kelvin]

Be careful how you word this, you may know what you mean here but OP isn't an electrician. Loss of a phase through a three phase mcb alone will not cause it to trip whether from the supply side or broken wire load side, having said that and as you noted in previous post it may cause excessive current rise in other phases and this will depend on the load and its characteristics i.e. if a 3ph motor connected then it will 2phase on start-up giving high current spike on the stalled motor until it is detected by the motor overload or mcb or if poorly designed install/control circuit then until the motor catches fire and shorts

Oga does your breaker have overload function or capacity. If yes then single phasing automatically gives more load to the remaining 2 phase which depending on the breaker's rating as against the load can either trip or withstand the load. Hence, on installation every breaker rating should be a little more than the load that is given to it.

 

[Darkwood]

Oga does your breaker have overload function or capacity. If yes then single phasing automatically gives more load to the remaining 2 phase which depending on the breaker's rating as against the load can either trip or withstand the load. Hence, on installation every breaker rating should be a little more than the load that is given to it.

This thread is 8 yrs old, I can confidently say it has been resolved imho, please cheque the time stamps on thread/posts before responding.

 

[ruston]

This thread is 8 yrs old, I can confidently say it has been resolved imho, please cheque the time stamps on thread/posts before responding.

It was nice to see some old names though, especially Engineer54.

 

[Rockingit]

It was nice to see some old names though, especially Engineer54.

Another RIP, sadly.