3 Phase 3 Wire Electrical Service (No Neutral)

[roger]

So why mention it in post#2 if it is an irrelevance?

Hmmmm, just a guess, might it have been simply to confuse you.


Roger

 

[meternerd]

We (utility) used to supply that kind of service for our pump stations, but we're phasing them out to 480/277 Wye. Reasons have been discussed here at length. Lots of possible issues with ungrounded 480, corner grounded 480, etc. But, if it's 480/277 grounded neutral, then Code requires that a neutral wire be brought to the service even if it's not used. Sometimes there's no room in the service conduit, so conversion costs go way up. By the way....moved out of California, finally. Now in northern Idaho. What a relief!

 

[kwired]

Maybe an existing service but building use is being changed?

In many cases like that though it would be desired to change the service to something more suitable for the application. You typically have two choices - put money into updating the service or put money into installing separately derived systems to get what you need.

 

[Tony S]

This may be helpful to the OP http://static.schneider-electric.us/assets/consultingengineer/appguidedocs/section6_0307.pdf.

An artificial neutral can be created on an ungrounded delta supply using a ZigZag Yn secondary transformer.

 

[Jraef]

One major disadvantage to using 480V delta (grounded or not) for an office building is that anything with a diode bridge rectifier or Switch Mode Power Supply (which is virtually everything now) connected to the 480V supply directly, will be subject to damage in the event of a ground fault anywhere on the system if special precautions are not undertaken. A typical HVAC contractor installing a VFD for the air handler will have no clue on that issue and the end user will suffer the consequences.

Why is this even being considered?