transformers

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dshelley

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I am hooking up a line voltage input of 208 y volts to a 240 low voltage delta transformer with a 480 delta high voltage. The contractor that installed it said it was an illegal application and shut it down. is this true?
 
I see no reason to call it illegal without additional information. Of course, you do realize you will only have 416V on the output unless the transformer has taps that provide a 208:480 ratio.
 
transformer

transformer

is their a grounding issue, I see no reason either ia is actually putting out 441 volts on the high tap and it is a multitap transformer
 
dshelley said:
is their a grounding issue, I see no reason either ia is actually putting out 441 volts on the high tap and it is a multitap transformer
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You either need to corner ground your HV delta, or provide ground fault alarming.

Taps work best when they are o the 'input' side of the transformer.
 
jim dungar said:
I see no reason to call it illegal without additional information. Of course, you do realize you will only have 416V on the output unless the transformer has taps that provide a 208:480 ratio.
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I'm not discussing the code issues, just a physics question (and a transformer design question):

240 is right at 20% above the design input. Wouldn't this tend to drive the core into saturation? I don't know what size this transformer is, but aren't most small "comodity" transformers (say below 100kva) built as light on iron and copper (or aluminum) as the mfg can do? This is my reasoning why the increased voltage would tend to drive the core into saturation.

cf
 
Cold Fusion said:
I'm not discussing the code issues, just a physics question (and a transformer design question):

240 is right at 20% above the design input. Wouldn't this tend to drive the core into saturation? I don't know what size this transformer is, but aren't most small "comodity" transformers (say below 100kva) built as light on iron and copper (or aluminum) as the mfg can do? This is my reasoning why the increased voltage would tend to drive the core into saturation.

cf
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The way I read the original post, it looks like the opposite situation: transformer rated at 240 V, only 208 V applied.

I'm wondering why you would want to do this? Are you trying to drive 480V loads? Why not get a transfromer with the right voltage ratings??
 
Cold Fusion said:
I'm not discussing the code issues, just a physics question (and a transformer design question):

240 is right at 20% above the design input. Wouldn't this tend to drive the core into saturation? I don't know what size this transformer is, but aren't most small "comodity" transformers (say below 100kva) built as light on iron and copper (or aluminum) as the mfg can do? This is my reasoning why the increased voltage would tend to drive the core into saturation.

cf
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Steve66 is correct, they are feeding a 240V coil with only 80% of voltage. This will impact the loading capacity of the transformer. Because a transformer is basically a motor that does not turn, voltage variances will be similar to a voltage starved motor.
 
cf, from a physics standpoint, do you see a problem connecting a 240 volt transformer to a 208 system ?
 
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