not an isolation xfmr according to eaton - then why?

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wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
I have to install three ups power mods/ 3 extended bat mods w 3 xfmrs.
I don't exactly understand the purpose of the xfmrs.
I asked eaton if these were isolation xfmrs for power quality and, how that worked w the ups because I know that sometimes UPS and isolation xfmrs dont get along. The rep told me the sole purpose of this xfmr was to provide a neutral to the load. Maybe it is an isolation xfmr after all.
Also doesn't this separately derived xfmr need to grab some building steel? Eaton says not.

Can anyone whose done a bunch of these help me understand?:angel:

its the
9PXTFMR11 11kVA Transformer
9PX EBM 240V extended battery mod
9PX 11000 VA UPS

Looks like the UPS is the main event and the battery mod and xfmr are accessories.
Two phase wires [208] go to UPS [w grnd]. It is rack or tower mounted next to the bat mod and there is a short connector for that.

Then there is an XFMR cable that sends the UPS'd pair [w grnd] to the xfmr.
On the xfmr a neutral is created from center point and
there are a number of cord and plug outlets or you can hard pipe to new distribution if needed.

To restate my question:
Doesn't this separately derived system need some building steel? Or better: a big wire back to the main?
Will these big ups's [connected to e-circuit dual feed switchgear at the other end] introduce noise into the system?
250.12 1 Use of Equipment Grounding Conductors An equipment grounding conductor shall not be used as a grounding
electrode conductor.
Exception: A wire-type equipment grounding conductor installed in compliance with 250.6(A) and the applicable requirements for both the equipment grounding conductor and the grounding electrode conductor in Parts II, III, and VI of this article shall be permitted to serve as both an equipment grounding conductor and a grounding electrode conductor.​

If the xfmr is not intended as an isolation xfmr, why not have just run a neutral with the two phase wires powering the ups and be done with it / save some money?

thanks
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If the output of the inverter in the UPS is only 240 volts, then a transformer, which could be either an isolation transformer or an autotransformer (more likely) will be needed to create a neutral point for 120 volt loads.
Such a transformer would also allow the 120 volt loads to be unbalanced.

Tapatalk!
 

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
and it doesnt need special gec because
1. eaton says so
2. auto xfmr so it may not even be an sds
 
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