Question Regarding step down transformers.
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  1. #1
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    Default Question Regarding step down transformers.

    I just purchased a new used Hwacheon Hi-ECO 21hs lathe. There is no tag on the machine specifying voltage and I do not have a manual for it, but I am fairly certain it is currently wired for 208 wye 3 phase (still waiting to hear back from the previous owner to confirm) . The power in my shop is 480/277 3 phase, so I will need a step down transformer.

    I have some older transformers wired up in the shop that used square d 15t3h transformers, but these are no longer sold.

    I called the local electrical supply place and they recommended Jefferson 423-9164-000 as the alternative they carry.
    I took a look at the specs online and it says the primary voltage is 480 delta, while my shop is 480 wye.

    Is it just a matter of changing taps for a wye to wye setup? Or do I need to look for a different and specific Wye to Wye transformer?

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    The voltage between legs is 480 in both cases, so it shouldn't make a difference. The only thing you should need to worry about is whether you need a common on the output.

    Bill

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    My suggestion, member 9100 should change his screenname t too something less like as9100sd...

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    Quote Originally Posted by Mike1974 View Post
    My suggestion, member 9100 should change his screenname t too something less like as9100sd...
    It would be really hard to confuse these 2 guys.

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    Quote Originally Posted by Mike1974 View Post
    My suggestion, member 9100 should change his screenname t too something less like as9100sd...
    AFAIK, I had my nom de net long before he had his. I got mine because when I signed up for PM, everything I could think of was in use. Finally, in frustration, I entered the model number of my Hewlett Packard scientific calculator and that was accepted. Note that I am coming up on 16 years in PM.

    He is welcome to change his.

    Bill

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    Quote Originally Posted by 9100 View Post
    The voltage between legs is 480 in both cases, so it shouldn't make a difference. The only thing you should need to worry about is whether you need a common on the output.

    Bill
    Mine is not for changing Voltage, its 1:1, but Delta-in, Wye-out, specifically because I DID want a "re-derived" local Neutral.

    So IF - and it may not - but IF... the new machine needs such, then EITHER of Wye-Wye or the more common Delta-Wye (EGS / Hevi-Duty) will provide it.

    As Bill says - it is all about the delivery or output side.

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    I spoke with another supply place that was more helpful than the first. They said the transformers can be configured for either 480v wye or delta but there is a difference in wiring it (somthing about backfeeding? I didn't catch it all over the phone)

    He is going to send me some of the wiring diagrams, I will post some more info here when I have it.

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    The first supplier gave you the correct transformer type, that you would need for a 480V to 208V stepdown transformer. Jefferson 423-9164-000 is a 15KVA unit, 480Delta to 208Wye. You don't need or want at 480Wye for the input side, that would cause huge circulating currents in the system, if connected that way. You just need 3 480V hot lines and a equipment grounding wire to feed it, no neutral wire required to feed the transformer input.

    You do want a wye connection on the 208V output side, in order to properly ground the transformer output coil. I wouldn't order anything until you determine what the actual machine requirements are for voltage and current. You don't know if that KVA size is appropriate for the load. Or if the voltage is the correct one for your needs.

    Jefferson Catalog

    15kva-jefferson-480-208-connection-diagram.jpg

    SAF Ω

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