New Help Finding an Isolation Transformer

Henderson

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I need some help selecting an isolation transformer. What I'm looking for is a transformer that will have 240 single phase on the input side, and will provide my with 240V split phase on the output side. The output side would therefore have the center tap, which will provide 120 from L1 to center tap, 120 from center tap to L2 and 240 between L1 and L2. I'm looking to pair this with 240V inverter. Would appreciate any suggestions/recommendations. Thanks in advance.
 

timselectric

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Ebay is the best option for the money.
Search for a 5kva single phase transformer.
 

Larry Oswald

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Just today I stumbled onto the GE/Square D line of transformers 9T51Bxxxx ranging from the 0007 to the 0013 and higher. Look for them on eBay and/or Facebook Marketplace and even Craigslist. I bought a 3KVA (55 pounds) 9T51B0013. There are other brands also.

Here is a small one

Slightly bigger

3KVA like mine. Good price.

ANY COMMENTS ON THESE TRANSFORMERS??
 
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timselectric

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Just today I stumbled onto the GE/Square D line of transformers 9T51Bxxxx ranging from the 0007 to the 0013 and higher. Look for them on eBay and/or Facebook Marketplace and even Craigslist. I bought a 3KVA (55 pounds) 9T51B0013. There are other brands also.

Here is a small one

Slightly bigger

3KVA 60 pounds. Good price.

ANY COMMENTS ON THESE TRANSFORMERS??
First two are too small for any system. Third one is too small for most systems.
You need to match your transformer size to the inverter output. KVA should be equal to or higher than KW. Not perfectly equal, but close.
 

Larry Oswald

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Fair comments Tim. Here is a question. If one has a charger inverter that produces only 220VAC from either PV or battery would a 3KVA (3KW) transformer serve to establish a neutral connection (split phase) for small household appliances, like a night time critical loads panel somewhat mitigating the unbalanced loads problem? I am thinking if the fridge turns on then off while the TV and computer are on. These loads are below the 3KW threshold. I am thinking grid not connected at all. Without establishing a neutral the voltages could fly around well over 120VAC on one side and correspondingly low on the other. Won't this center tap hold that?
 

timselectric

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Fair comments Tim. Here is a question. If one has a charger inverter that produces only 220VAC from either PV or battery would a 3KVA (3KW) transformer serve to establish a neutral connection (split phase) for small household appliances, like a night time critical loads panel somewhat mitigating the unbalanced loads problem? I am thinking if the fridge turns on then off while the TV and computer are on. These loads are below the 3KW threshold. I am thinking grid not connected at all. Without establishing a neutral the voltages could fly around well over 120VAC on one side and correspondingly low on the other. Won't this center tap hold that?
Maybe
It would be limited to 12.5 amps. But, I wouldn't want more than 10 amps running through it.
 

Larry Oswald

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First two are too small for any system. Third one is too small for most systems.
You need to match your transformer size to the inverter output. KVA should be equal to or higher than KW. Not perfectly equal, but close.
Tim.
I am not an electrician but I have taught Physics. A transformer does not load the input circuit until the secondary is connected to something. It would be OK to connect a 3KVA transformer to a 220VAC 10KW inverter output so long as you do not try to suck 10 KW out of the transformer. The inverter can be parallel connected to a 220VAC load and to the smaller transformer. A Tesla power wall could directly feed the grid pure 220VAC at night while a connected center tap transformer could run the fridge, TV and microwave. I think this is true.
 

timselectric

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Tim.
I am not an electrician but I have taught Physics. A transformer does not load the input circuit until the secondary is connected to something. It would be OK to connect a 3KVA transformer to a 220VAC 10KW inverter output so long as you do not try to suck 10 KW out of the transformer. The inverter can be parallel connected to a 220VAC load and to the smaller transformer. A Tesla power wall could directly feed the grid pure 220VAC at night while a connected center tap transformer could run the fridge, TV and microwave. I think this is true.
You can connect it to any size service. You just have to protect it to its rating. So that you can't pull more current through it than it can safely handle.
I said maybe, because I don't know what your appliances draw. If they draw less than the transformers rating, then yes. If not, then no.
 

Tecnodave

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Just today I stumbled onto the GE/Square D line of transformers
General Electric Corporation DOES NOT own Square D, never has,

Square D is a wholly owned subsidiary of Schneider Electric,

before Schneider Electric (Germany) purchased Square D (1990’s ?) they were a American company dating back to the early 1900’s

I retired from GE and am a stocking installer of Schneider and Square D ( (NOT including Schneider Solar).
 

RCinFLA

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Larry Oswald

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General Electric Corporation DOES NOT own Square D, never has,

Square D is a wholly owned subsidiary of Schneider Electric,

before Schneider Electric (Germany) purchased Square D (1990’s ?) they were a American company dating back to the early 1900’s

I retired from GE and am a stocking installer of Schneider and Square D ( (NOT including Schneider Solar).
Dave is right. My brand confusion. SquareD makes the same kind of transformers. Here is a 5KVA. $2748.13


Notice the wiring diagram 208VAC to either/both 120-240VAC and especially the secondary center tap (split phase) option. I have never used one of these transformers but I have two coming. I grabbed a 1KVA unit for fifty bucks.
 

wmgeorge

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UPS can take up to 120 lbs I believe, had a lathe bed shipped to me that kind of stressed that. Wither or not UPS can ship with out major damage????
 

Larry Oswald

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UPS can take up to 120 lbs I believe, had a lathe bed shipped to me that kind of stressed that. Wither or not UPS can ship with out major damage????
UPS Freight is delivering my 55 pound 3KVA unit today. My smaller 1KVA (fifty bucks) arrived yesterday (USPS) in great used condition. It had a pile of wiring inside making my games easy. It was connected for 480VAC input and 120VAC output, likely for lighting. The wires are all labeled with the input Hs and output Xs.
 

wmgeorge

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UPS Freight is delivering my 55 pound 3KVA unit today.

Not by truck Freight I hope but via regular UPS, correct? The H and X terminals marking are SOP for those transformers.
 

Larry Oswald

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UPS Freight is delivering my 55 pound 3KVA unit today.

Not by truck Freight I hope but via regular UPS, correct? The H and X terminals marking are SOP for those transformers.
Yes our regular UPS guy. He claimed the box was 70 pounds but he was getting even for me asking him to take it up on the roof. My comment on the Hs and Xs is that the LABELS were there. Nothing was snipped off. Second 3KVA was also connected for 480 to 120 so I am rearranging them for 220VAC split phase. Great light duty solution for all the cheap Chinese 240 VAC outputs inverters.

Edit: Some deals are great and some poor and then there are some in between. These transformers have two windings on both the primary and secondary making them very versatile. Problem with my 3KVA in the X3-4 secondary winding. Its voltage is 20% low meaning too few windings are working. This I test using a little 10VAC Radio Shack plug in supply from the last century. The in 10.2VAC in and 4.1 and 5.0VAC split "phase" out. That would be one leg about 95 volts when fed with 240VAC. I have written to the seller who has hundreds of items on eBay. One could use this unit to make from 240VAC ONE good leg of 120 volts and 12 amps. Can be useful but no prize.
 
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