3 Phase supply calcs.

[dlt27]

Hi and thanks in advance,
I have been asked to provide a new supply for a factory unit. They want supplies to welding bays, metal cutting saws etc. The only info I have been given is that they want a 250A(3 phase) supply from existing 600A panel (PME) to a sub panel and then from sub panel a supply to compressor(runs at 70A per phase) and 1 x 63A supply to 1 small 3 phase board and 100A supply for welding 3 phase distribution board.
I wondered if anybody could give advice on calcs etc. for working cable sizes. At my old company it was all provided and I just had to install. Now I'm self employed I want to be 100% sure I'm doing it correctly. Obviously I know I need to take into account volt drop, max zs for 250A MCCB etc.
I have got a rough idea of what sizes I believe I need, however didn't want to show working as I didn't want to get shot down by more educated people than myself. I was going to run separate earthing conductor with SWA's to meet bonding requirements.
I am obviously not going to commence work until I am 100% sure of sizes. I have done calcs on apps etc, but would like to go through everything so understand for future.
I understand 2 phase welders need balancing across phases etc and max volt drop from 600A panel to lighting and power are 3 and 5%.
I totally understand if it is too time consuming for somebody to explain or go through it, however it will be greatly appreciated. Thanks again

 

[Leesparkykent]

What length are the circuits and how are they to be arranged? Do you know the Ze? Installation method? what make is the 600A panel board?

 

[dlt27]

80m for 250A supply to new panel, From new panel -15m for 63A DB, 30m for compressor, and 30m for 100A DB. Ze =0.05 Thanks

 

[Leesparkykent]

80m for 250A supply to new panel, From new panel -15m for 63A DB, 30m for compressor, and 30m for 100A DB. Ze =0.05 Thanks

On tray, clipped direct, buried in the ground etc?

 

[dlt27]

250A on tray on its own. 63A DB on tray on its own. 100A DB and compressor are buried in the ground in ducting then on tray together to final positions. Thanks

 

[Leesparkykent]

What make and model is the 250A MCCB?

 

[dlt27]

I need to check. I know its square D, but unsure of model. I took max zs for 250A mccb off the website. Thanks

 

[dlt27]

Any help please..

 

[Leesparkykent]

Any help please..

Hi mate, sorry was going to enter it into the amtech software today but didn't end up making it in to the office as had a busy day on site. What was the max Zs of the 250A MCCB?

 

[LeeH]

I'll do you Amtech calc and drawing for a small fee...

 

[dlt27]

Looking in the panel it says cn range so on square D sheet looks like 0.09. Really appreciate it. Is amtech worth the money. Thanks

 

[dlt27]

What fee? Thanks

 

[Darkwood]

Hi - dlt27

It would help us greatly if you can show us your calcs and the cable sizes you end up with, we can then point out any errors or add further queries for you to answer or hopefully confirm they are correct. Its asking a little beyond our kind nature for us to do it all for you and provide the design although if any member wishes to then that's fine, if we can give us some idea here what you have come up and how then we are more than happy to help.

Things to consider -
- Discrimination between devices.
- What distribution system you wish to install be it a busbar setup or Powerboard.
- Will the installation require corrective measures for the welding equipment (Power Factor Correction).
- Bonding if your running into other factory units.

 

[dlt27]

I will go through it and put it on here tomorrow.
I wanted someone to go through process rather than do exact calculation. Thanks

 

[Darkwood]

I will go through it and put it on here tomorrow.
I wanted someone to go through process rather than do exact calculation. Thanks

Appreciate that, just trying to make the thread more concise otherwise it becomes a lengthy question and answer thread, if your using MCCB's against final distribution mcb boards then for full discrimination you will probably need an upstream device covering it of 160amp, if I recall to cover this 160amp device you would need a 400amp for full discrim' ... who has specified the 250amp?
Can you just draft a little block sketch of the proposed submains and circuits so we can better visualise your set-up.