Settle a bet on transformer

[Karl_T]

My son just bought a waterjet that only runs on 440. BTW He STOLE IT. This one with low hours https://www.omax.com/omax-waterjet/55100

There was an auction last night with three different transformers. The one he wanted went $1200. With premiums it waas too close to the scatch'n'dent one he can get from an electric supply place with warranty.

I said this one is mis-lableled, it will work to step 220 3 phase up to 440 three phase. He bought it and said i owe him $100 if wrong.

https://www.k-bid.com/auction/42369/item/107?offset=108

Look at the pics. I see one set of lugs on top for lo volts and another on the bottom for hi volts.

 

[Eddyde]

You think its a Buck-Boost not an Isolation transformer? Could be, is there any spec plate on it?

 

[Karl_T]

You know as much as i do. we just bought pictures. Pick up day is Friday.

I am spending the weekend helping with set up.

 

[Eddyde]

I tend to believe you are correct, the "P" for primary and "S" for secondary. Looks like it was used to buck the voltage down from the 300-400v range to 200v range. Theoretically it should work in reverse, just fine...

 

[RJSakowski]

A buck/boost transformer is an autotransformer meaning different taps on the same winding are used to obtain the desired voltage. A common autotransformer is a Variac, There will al ways be an electrical connection between the primary and secondary voltages.

In comparison, a typical transformer would have two windings, a primary and a secondary winding. The ratio of voltages is equal to the ratio of the number of turns. and the two voltages are completely isolated from each other. The difference can easily be determined with a continuity test with an ohmmeter.

A transformer can be generally used in reverse. That is, a transformer which generates 240 volts from 120 volts can be used to step 240 volts down to 120 volts. There are some caveats to consider though. An extra winding or do may be added to a transformer to compensate for resistance losses in the windings so the voltages in reverse may be slightly off the ideal. The ratio of no load voltages, V1/V2 = n1/n2 will hold true but there may be a deviation from this under load, depending on how well the transformer is built. The significant variation between no load voltage and voltage under full load is more common for cheaper transformers.

 

[markba633csi]

You may or may not need those three little straps on the low voltage side, but it should work fine- looks brand new!

 

[Bi11Hudson]

Up front, take resistance readings between the P(rimary) and S(econdary) windings. If there is none, ie open circuit, you have a voltage matching transformer. A great deal of equipment comes out of Europe, where 360 volts is common. The setup is designed to work in both directions, ie (US) high in, low out and (European) low in, hi out. What you are looking for is 240 volts on one side and 480 on the other. The many taps will allow some of the winding to be unused. Just insulate the unused taps and ignore them. Unlike "standard" industrial power transformers which have 120/240 on one side and 240/480 on the other, this transformer uses taps.

The next step is to isolate the windings, usually just removing straps or jumpers. There should be six windings, three pairs, providing 3 phase ability. Phasing is an important issue. The final connections MUST be sequenced together.

A three phase load may be driven by an "open delta" configuration, at reduced current of course. Essentially getting three phase transformation from two transformers. The current is limited to less than 60%, but is doable.

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