Hi guys. Im having trouble finding a suitable 277v VT. I went through the iotawatt list and the ELCO Lighting ETR12-277 isnt available. Either they’re 277 to 120v or 120v to 12v. Amazon,ebay shows nothing, and my order on buyriteelectric canceled my order. Any help with this. Location: USA
Second question is also about VT’s.
I have have a 480v main panel and 2 step down transformers with thier own respective sub panels. Can I just use one voltage transformer with derived reference on the 3 phase 480v and just put ct’s the sub panels or do I need 120v VT’s on each sub panel in addition to the 277v VT on the main incoming 480v?
Too bad ELCO dropped that, they worked very well. I think you have a few more options.
I’m not sure if this would be suitable, but I would be willing to try one out and see.
The other option is to use a 120V transformer from one of the subpanels. the big 277V:120V stepdown should have negligible phase shift, so I don’t see a problem. It all comes from the same feed, so should have the same phase and voltage should be proportional.
You don’t say if the subpanels are three-phase or split-phase. If they are split-phase, you would definitely need to use derived reference. If they are three-phase, you can use three 120V VTs if you want to use direct.
You would use the reference for any CTs in the subpanels.
If you want to put CTs in the 277V/480V panel, use a VT plugged into the 120V panel, or a splitter to duplicate the one you have, plug it into one of the additional VT jacks, and scale up the calibration to equal the voltage of the corresponding phase in the 277V panel.
Thanks, that helps clear vt questions and btw it is a split phase system on the sub panels so i definitely will use the derived reference. The hatch transformer you linked also led me to this one on amazon 50 Watt Magnetic Lighting Transformer - 277 Input Volt 12 Volt Output LS1250ENT-277.
I might give this one a try even though its more expensive.
I’d give it a try with the 120V transformer in the subpanel.