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    Default Transformer woes....

    hey guys, moved to a new shop that has 240v 3phase not 208 .. changed some of the legs on the transformer in my 2005 romi e320 (fanuc control), to accept the new voltage per Romi. It ran fine for a while.. a month after though looks like the transformer failed, and a tech i spoke to said that the leg on the transformer that had not been used since the machine was new might have been sitting without working for too long causing it to fail when under load.. no sign of anything else.. Thinking of putting a transformer outside the machine for the main power supply.. and going around the internal one, which is really tough to remove where the machine is, and would be costlier by a bunch.. Does anyone have experience doing this? also, where is a good place to look for a transformer for a cnc..
    it needs 50KVA 220 to 208 three phase

    thank you
    Zach

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    Never heard of a transformer failing from just sitting.

    Tom

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    Quote Originally Posted by zschary View Post
    and a tech i spoke to said that the leg on the transformer that had not been used since the machine was new might have been sitting without working for too long causing it to fail when under load..


    Zach

    Seriously?
    What exactly in a transformer needs a daily workout?
    The AL or CU winding?
    The Iron or laminated core?
    Or perhaps the flux?

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    Quote Originally Posted by zschary View Post
    hey guys, moved to a new shop that has 240v 3phase not 208 .. changed some of the legs on the transformer in my 2005 romi e320 (fanuc control), to accept the new voltage per Romi. It ran fine for a while.. a month after though looks like the transformer failed, and a tech i spoke to said that the leg on the transformer that had not been used since the machine was new might have been sitting without working for too long causing it to fail when under load.. no sign of anything else.. Thinking of putting a transformer outside the machine for the main power supply.. and going around the internal one, which is really tough to remove where the machine is, and would be costlier by a bunch.. Does anyone have experience doing this? also, where is a good place to look for a transformer for a cnc..
    it needs 50KVA 220 to 208 three phase

    thank you
    Zach
    Common as dirt and nearly as cheap in 480 delta to 208 Wye. Do you have 460/480 available, upline?

    Not as common nor cheap 220/230/240 Delta to 208 Wye. Not in 50 KVA and up, anyway.

    ebay will find them, and from "real" dealers of significant presence, eBay and OFF of it, not Grandkids selling-off G'mum's sewing basket trinkets.

    That said, a(ny) CNC with onboard transformer "usually" has a lot more going on than just the one output voltage.

    Have a look around at the transformers in the market as pulls from CNC part-outs. Hard to change OR externally mounted, you might find the same or at least more compatible transformer.

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    I just used buck transformers when I got a machine that needed a lower voltage.

    Ed.

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    Quote Originally Posted by zschary View Post
    changed some of the legs on the transformer in my 2005 romi e320 (fanuc control), to accept the new voltage per Romi. It ran fine for a while..
    Did you change only 2 legs of the transformer and not all 3 legs?

    I almost burned up a machine transformer in a matter of seconds when I only changed 2 legs. Started to smoke almost immediately after applying power.

    Lots of transformers on ebay.

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    No i am doing all three.. thanks for that tip..
    i have been looking on ebay.. will have to figure this out..

    thank you to all who helped on this.. Zach

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    Quote Originally Posted by zschary View Post
    it needs 50KVA 220 to 208 three phase
    Here's a Mitsubishi transformer out of a Mazak CNC lathe from ebay. The wiring diagram is glued on the inside of the removable cover. The transformers in my Mazaks have taps for various incoming voltages and put out 210 volts to the machine. Shipping might be a bit expensive but it would work for your machine.

    If you are interested, ask the seller to remove the panel and take a pic of the wiring diagram to verify this will work.

    Mazak M5N 53KVA Electric Transformer Input 200-480 V | eBay

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    Philabuster, thank you for the info.. I did find a 45 kva dry type transformer that will work.. The question i have is whether i need a disconnect in between the feed breaker going to the primary of the transformer, or will the breaker work.? so when i turn the machine on i would just throw the breaker at the sub panel, or should it have more of a dedicated switch?.. other way i could do it woudl be to go to the machine switch, then back out to the transformer then back in to the main breaker input at the machine.. I guess i would rather just use the breaker.. what do you think?

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    Quote Originally Posted by zschary View Post
    I guess i would rather just use the breaker.. what do you think?
    If it was me, I would put in a disconnect after the breaker.

    In my experience, circuit breakers in a breaker panel do not like it when there is a heavy load on the circuit when you turn on the breaker. They tend to just trip off as an overload right away.

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    Quote Originally Posted by zschary View Post
    Philabuster, thank you for the info.. I did find a 45 kva dry type transformer that will work.. The question i have is whether i need a disconnect in between the feed breaker going to the primary of the transformer, or will the breaker work.? so when i turn the machine on i would just throw the breaker at the sub panel, or should it have more of a dedicated switch?.. other way i could do it woudl be to go to the machine switch, then back out to the transformer then back in to the main breaker input at the machine.. I guess i would rather just use the breaker.. what do you think?
    Folks do that all the time out of convenience, but it is often WRONG.

    Many lighter amperage breakers are also rated as switches.

    Most heavier ones are not meant to be used as switches.

    Used-but-good major-vendor disconnects are cheap enough, fused and unfused.

    Put one where it makes sense for safety as well as convenience.

    This presumes your machine-tool ALREADY HAS the "starter" functionality that does NOT put power back on after a power interruption unless and until an operator CHOOSES to turn it back on.

    See "motor starter" for the general class if it is NOT already "there".

    Especially if there WAS one, but it got left-out in this power alteration plan.

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