ECN Forum Forums General Topics of the Trade General Discussion Area 240 Grounded B phase distribution

Steve I am confused.

I work in lot of IT rooms and the supply to an IT room will likely be delta but it is from a 4 wire grounded Wye source and when it is converted down to 208Y/120 that is also grounded.

The only ungrounded systems I run into are in industrial buildings with motor loads and continuity of supply issues.

The 208V/120Y is always grounded wye, yes. The primary can be anything, though.

Where does the 63V come from if the supply is a true delta configuration and there is no other ground reference on the system?

We use a 110Y/63V system on large building sites in the U.K. for the handheld 110V power tools. The secondary is wye though, and the neutral point is always grounded, thus limiting the potential on any hot leg to 63V with respect to ground.

There is no ground reference- when balanced, though, each phase will be 63V from the ship's hull, thus limiting shock potential to 63V. Calling it 110/63V is incorrect with that respect, I was just trying to demonstrate the point about safety. It's always simply referred to as 110V delta.

[This message has been edited by SteveFehr (edited 11-12-2006).]