3 phase wiring

[PTR]

If you have a 2hp motor on a milling machine What size cable should you use?
Yesterday I was told it should be 4mm2, this morning 2.5mm2.

I need 3phase, neutral and earth

Any suggestions on how to calculate or better still the correct answer.

Cheers[/img]

 

[breezer]

3phase AND neutral? that doesn't sound right unless it has some type of "controls"

any way, that aside, what exactly does the label on the motor say?

and if it is 3 phase i take it this m/c is not at home?

 

[PTR]

The miller has an integral digital readout and variable speeds to both head and feed. It also has coolant pump which we haven't investigated yet.
You are correct it isn't at home so I will check the motor details tomorrow when i go into the workshop.

We also have a "new" lathe which requires the same connections again with a 2hp motor and variable speeds. So I hope to find one solution for both machines.

 

[breezer]

the next obvious question is does your property have a 3 phase supply?

and here is the downside, you can not work on 3 phase you will have to get an electrcian in to do it all for you

 

[oilman]

If it is 2hp, that's 1500W or 500W per phase. Allow for phase angles and some margin, say 4A per phase, so 1mm2 cable would do it. Neutral should be carrying near zero current anyway. Therefore 2.5mm2 would be ok.

Why not reconnect the motors to "DELTA" (if not already) and run them using a variable frequency inverter from a single phase outlet?

 

[PTR]

Thanks Oilman

This is most helpful.

I have checked the machines today and the Lathe has three motors:- 11/2 Hp main motor, 1/15 hp motor on the feed control and a 1/2 hp on the coolant system also rated at 0.18A.

The miller has a 2hp main motor and a 1/2 hp coolant pump. The side plate indicates a max of 16A for the machine.

So from your information we should be ok to use the 2.5mm cable?


Breezer,
Yes we have three phase available and for info it was two fellow electricians who gave me differing information.
As I have only been undertaking domestic/commercial work since serving my time 20+ years ago I thought I would check up on the industrial side before commencing work.

Better safe than sorry don't you think.

Cheers.

 

[Jimster]

PTR, can I come and play in your workshop, sounds like you've got some good toys there,

 

[PTR]

Sorry Jimster,
This one is only for big boys who like big toys.