Voltage Drop on cabling

[Simple Simon]

Good morning All,

Ive been asked to work out the potential volt drop on 12 metres of 10mm x 7 core SWA powering a 45kW (60hp) motor.

Just to check my findings as below, please could someone confirm whether I have done it right.


45kW - 80amp FLC

as using Star Delta Starter

multiply by 0.58 = 46.4 amps

10mm x 7 core SWA has acarrying capacity of 58 amps per phase.

The voltage drop I believe is 4.0mV per metre multiply by 12 metres = 48mV which I also believe to be around 0.06 of an amp.

Best regards

Simon

 

[Brightspark2]

mV/A/m x current x length

Divide by 1000

 

[Knobhead]

Why not use two 3 cores in parallel? You don't need a CPC.

 

[Darkwood]

I prefer flexicon with tri- rated alot easier with the lugging up in the motor terminals i relax this personel rule of thumb with cables <10mm as they aren't as awkward to manipulate into position.

 

[Knobhead]

Flexicon for 12M ?

 

[Darkwood]

Flexicon for 12M ?

No! suitable adaptabe box mounted close if possible with din connectors then last couple meters in flexicon ... or even trunking systems to flexi' job dependant... i try design a machine install so maintenance etc isn't a major hurdle so most of my control cabs are harting connectors linked can all be unplugged for resite, maintenance and testing etc.....

Its only when limited by job would i do an armoured but 10mm border for me but 16mm up id always try get the final connection in tri-rated unless im blessed with a tanked sized old DC beast with a Wendy House sized terminal block.

 

[shanky887614]

No! suitable adaptabe box mounted close if possible with din connectors then last couple meters in flexicon ... or even trunking systems to flexi' job dependant... i try design a machine install so maintenance etc isn't a major hurdle so most of my control cabs are harting connectors linked can all be unplugged for resite, maintenance and testing etc.....

Its only when limited by job would i do an armoured but 10mm border for me but 16mm up id always try get the final connection in tri-rated unless im blessed with a tanked sized old DC beast with a Wendy House sized terminal block.

thats the way we have done on 10+ pump sets on this job

4" trunking for power with tri-rated cables to isolator then from isolator in tri-rated

40 ish+ metres per pump

 

[Knobhead]

Adaptable box = terminals. Flexicon = weak containment.

2 X SWA direct to motor = no unnecessary terminals + tough as old boots and no CPC.

No contest!

 

[Darkwood]

Adaptable box = terminals. Flexicon = weak containment.

2 X SWA direct to motor = no unnecessary terminals + tough as old boots and no CPC.

No contest!

Never had a issue ever with extra set terminals and maybe i should be clearer Flexi' conduit not namely flexicon i use the expensive stuff IP rated chemical resistant and high durability and again its never failed me, i think this just comes down to individual pratices and we will both defend our own but both methods completely fine if done correctly.

 

[Engineer54]

I'm happier with flexible connections to motors, especially where motors can be subject to vibration or movement, but i've used SWA and even MICC direct motor connections... Where you need to be a lot more savvy and confident on method of direct connection... lol!!

 

[Spoon]

All depends on the install with me. I have gone both ways. Used trunking and then conduit to motor and also SWA direct to motor.

 

[Knobhead]

If a motors vibrating the cable is the least of you’re worries. Plant vibration will generally have everything vibrating together. If it isn’t you really are in trouble!

My only experience of MICC on Dahlander motors was a nightmare, it would fracture at the junction were it was connected to cambric cable. It was on the lifting beam of a hot (molten) metal crane so not a typical installation.

 

[kingeri]

Blimey, puts my house-bashing exploits into context

 

[benji]

starter to motor 10-12mtr would a local isolator be needed

 

[Darkwood]

The supply to the machine or control panel that operates the motor will have its own local means of isolation, the motor in itself is part of a larger system, if deemed to pose a hazard for example if it was located in a seperate room and came on automatically it could have an isolation point fitted for safety in the instances of maintenance and testing but depends on the set up as appropriate warning notice may suffice if its capable to lock off the supply elsewhere, some of the machines i work on are 30+ m long with motors along the length but simply switching off the main machine isolation point and locking off is all thats needed to work on any motor.