Buck issue

[chris kennedy]

I have a situation where I'm trying to buck a 240 delta to 208 and need the line to ground voltages to be within 10% of each other. What I'm getting is 189, 120, and 90. My line to line voltages are good.

Any idea if the is a way to balance that out?

Thanks

 

[iwire]

You are out of luck, you will need a regular transformer to accomplish that.

 

[GoldDigger]

I have a situation where I'm trying to buck a 240 delta to 208 and need the line to ground voltages to be within 10% of each other. What I'm getting is 189, 120, and 90. My line to line voltages are good.

Any idea if the is a way to balance that out?

Thanks

What are the line-to-ground voltages in the original delta? (presumably with a wye center grounded neutral???)
If you are starting with a balanced voltage delta, you will have to "rotate" the three phase lines using a buck transformer across each of the phases, with the three primaries being phase-to-phase and none of the original line terminals being used for the load.
That is, with primary from L1 to L2, the buck winding goes from L1 to L1', the new phase terminal.
primary L2 to L3, buck goes from L2 to L2'
primary L3 to L1, buck goes from L3 to L3'
For a wye you can just buck the individual phase-to-neutral voltages, maintaining symmetry even if the load is wired as delta.

 

[chris kennedy]

You are out of luck, you will need a regular transformer to accomplish that.

Yeah, hopin for a miracle. Got one coming in this morning.

Here is what I don't understand. Wiring a big printer that makes the wraps you see on the sides of semi trailers. Takes 3 ungrounded conductors and an EGC, no grounded conductor. If the line to ground voltages are not within 10% of each other the ballasts used in the drying process won't operate properly. How can this be if the ballasts don't see 120V to a grounded conductor???:blink:

 

[kwired]

Yeah, hopin for a miracle. Got one coming in this morning.

Here is what I don't understand. Wiring a big printer that makes the wraps you see on the sides of semi trailers. Takes 3 ungrounded conductors and an EGC, no grounded conductor. If the line to ground voltages are not within 10% of each other the ballasts used in the drying process won't operate properly. How can this be if the ballasts don't see 120V to a grounded conductor???:blink:

Are they by chance wye connected but have a reference to the equipment ground somewhere at the common point of the wye?

 

[GoldDigger]

Are they by chance wye connected but have a reference to the equipment ground somewhere at the common point of the wye?

Perhaps the ballasts are deliberately wired to power a small control circuit through current to the EGC, as in early presence sensors?
Or the ballast (maybe during starting?) is somehow affected by the capacitance to a grounded metal shell around the lamp?