Topic: Anyone using 8300V to 208 or 240 directly? (Read 337 times)

I had a feeling about where this was going...
DISCLAIMER OF LIABILITY: OPINIONS GIVEN HERE BY ME IN NO WAY ARE TO BE CONSTRUED AS ENGINEERED DESIGN GUIDELINES!

I'm very serious about that as I *am* an EE and that carries liability in this case. I AM NOT a state-registered PE (Professional Engineer) and building electrical design is certainly not my profession.

That said...
It sounds very much like you are actually are going to do a large power installation. If this is not just idle 'why' speculation then YOU MUST CONSULT A COMMERCIAL/INDUSTRIAL ELECTRICAL DESIGN ENGINEERING COMPANY. Only a Registered Professional Engineer specializing in large commercial or heavy industrial power distribution systems is legally qualified to make these design decisions. Above and beyond that the building permits you will need to get require design plans to be filed with the city/state/whoever. Those plans literally require a PE stamp of approval on each and every plan. Period. End of story.

That said and strictly as a casual observation of what is done in large factories where my companies multi-kw hungry equipment (industrial lasers) and ancillary equipment are installed, yes odds are the design firm will go with 480v as the building distribution voltage. If anything, because at 480v the main switchgear 'only' has to handle 6,250A to deliver 3MW vs needing to be rated for 12,500A at 240v.

Frankly it would not surprise me if they go as high as 1.2kv for distribution as 3MW total load is certainly in the range to at least consider moving up to a MV (Medium Voltage) distribution network. Mainly would depend on the physical size of the farm and how far between the main panel and final step down transformer load points.

Got it...So if I am setting up 3 MW should I go for below?

1) Direct Utility Voltage i.e. 13000V to 240V or 208 V?
Or 2) Direct Utility Voltage i.e. 13000 to 480V and then Step Down From 480 to 240 or 208V?

Thank you.

That's different.
It depends on the physical size of the factory/mine and what their equipment uses. For new construction needing heavy power it is always better to distribute or use 480 because the wire or bus bars running across the plant can be much smaller and same with the secondary of the main step down transformer (read: less copper, less expensive). The only time they would step that down to 240 is if machinery cannot direct take 480V and yes, that is done local to the equipment.

That said, since miner PSU's take 208-240v and if you are planing for around 200kw or less go with 208-240v option. Just all around easier especially since that size mining op would be fairly small in physical size.. Start pushing more than that and running power feeds more than a hundred feet or so then using a higher distribution voltage becomes more attractive.

Pardon my ignorance  but I wanted to ask if it is advisable to do so...Sometimes people come up with reasons and experiences of why some things should not be done in one way or the other. I have been to mining farms where they purchased their own 3 MW 8300 to 480V primary transformer and then smaller 250 KVA step downs to 240V. If they are buying the primary why would they not just buy a 3 MW 8300 to 240 or 208. That gave rise to this question in my head. Thanks and do let me know

Pardon my French but -- what the hell do you think a 8.3kv to 208 transformer is?  
It's a very common step down service transformer from utility grid voltage to end-user voltage...

Hi Guys,

Anyone using 8300V to 208V or 240V directly instead of using a step down? How's the experience? Is this advisable to do? Thanks.