Circuit design

[markjenks]

Hi, after abit of advice.

Wanting to install a new aditional circuit for a lathe. Technical info on label says this lathe runs at 3 phase, 2500 rpm 54A. There are already Lathes installed with same spec but circuits installed to run these are currently BSEN 60898 type b breakers, using 4mm single core PVC, with cable run length approx 10-15M. Rather than just installing what's already in, I wanted to check all sizes, breakers, cable etc. My calculations come back much higher than what's already installed although everything is working and tested out/certified ok?
Any ideas what I could be missing when following cable calc procedure through BS7671?

Cheers. Mark

 

[Knobhead]

54A for a lathe? What the hell is it? A quick calculation gives a motor of 40HP!

I’ve worked on an 18’ X 30’ lathe, that only had a 25HP motor.

(It’s not a typo, 18 foot face plate and a 30 foot bedway.)

 

[telectrix]

maybe the 54A is total current of the 3 phases? or is there a decimal point missing? 5.4A?

 

[markjenks]

maybe the 54A is total current of the 3 phases? or is there a decimal point missing? 5.4A?

hi, thanks for your quick response. Maybe it is meant to be 5.4A rather than 54 as this is quite an old machine. I'll try putting the figures in for 5.4 see if they become any closer.

Thanks again.

 

[markjenks]

54A for a lathe? What the hell is it? A quick calculation gives a motor of 40HP!

I’ve worked on an 18’ X 30’ lathe, that only had a 25HP motor.

(It’s not a typo, 18 foot face plate and a 30 foot bedway.)

as this machine seems to be substantially smaller than the one you quoted, I'm going to presume there was a decimal point missing and try using them figures.

many thanks. Mark

 

[telectrix]

does the rating plate have a kW or HP figure?

 

[markjenks]

does the rating plate have a kW or HP figure?

Not on that lathe. There is a milling machine that also needs to go in. This has more info - 4.8A 2.475KW with rpm @ 4200
Is this any good as I'm having the same problems with this.

thanks, mark

 

[ackbarthestar]

54A 3-phase probably equates to 18A per phase giving 12.6kW rating (16-17HP). A 4.0mm2 SWA/SY should be able to cope with that sort of loading but it does, as stated before, seems a rather large machine to me.

What about the PF?

If it was as stated 5.4A then you'd be looking at 4kW or 5 HP - still a powerful machine....

 

[Knobhead]

You are talking complete and utter garbage.

A note to every one, look at the RPM!

 

[telectrix]

could the rpm be a typo, should be 2800?

 

[Marvo]

Yeah, something doesn't add up with the figures given. It would be an absolutely enormous lathe requiring that supply stated in the op.

 

[ackbarthestar]

You are talking complete and utter garbage.

A note to every one, look at the RPM!

Who?, Garbage ?, Moi ? - lol