transformer reverseal

[Big Rick]

I am instaling a machine that requires 220V 3ph
The transformer that I was given to install is a 3 ph ISO
primary 240 delta
secondary 480Y/277

is it possible to reverse this as I have 480 3ph power source.

 

[charlie b]

It is possible. But it might not be an acceptable solution. Much depends on whether the "machine" can be allowed to operate at an overvoltage of 9%. That is generally within the acceptable tolerances. But only the manufacturer of the machine can tell you for certain. Also, if the machine needs a neutral wire, then this proposed solution cannot work.

 

[LarryFine]

Added note: do not connect the transformer's now-primary neutral to the supply neutral; let it float.

 

[btharmy]

220v. 3ph.? Never seen such a beast. 240 or 208 yes. I'd check the machine documents for info.

 

[joel78]

electrician

electrician

In most of the transformers you can adjust the output voltaje by changing conection on the taps
10 years ago i was in a project wich i nedeed 400v three phase system\
for some european machinery
and i was able to get close to 400v

 

[templdl]

Is the transformer marked with "primary" and "secondary"?

Transformers are kind of dumb in that they simply step up, step down, or simply isolate having a simple 1:1 ratio.
The 240v side of your transformer should be marked with X1, X2, and X3. The 480Y/277 should be marked with H1, H2, H3, and H0.
Based upon the minimal infirmation privded in your post to use this transformer simply bring our 480, 3ph, 3w with the EGC. Terminating on H1, H2, H3, bonding the EGC to the enclosure. Leave the H0 insulated and isolated.
Connect you 240v to the 220v load. The problem that you may have is if you need to ground the 240v side. Since ther is no neutral as with a wye you may have no other options other than to corner groung it as in a grounded 'B' phase.
Depending upon the actual secondary voltage you end up with you may not need to make any voltage adjustments. If you do there should be taps provided of the 240v side which are commonly labeled a +(2)2-1/2% taps above normal and (2) or (4)2-1/2% taps below normal.
The name plate is commonly maked with the tap voltages 252, 246, 240, 234, 228, and is (4) below taps are included 222, and 216. In a normal application where you would be using this transformer to step-up you would select the tap that has the closest voltage to that which is being supplied to assure the you would have close to the desired 480v out.
When using this transformer as a step-down you can use these taps to adjust the output voltage to 220v but it would be dependent upon what the actual supply voltage is and if there are sufficient taps available to abtain the desired output voltage

 

[Besoeker]

In most of the transformers you can adjust the output voltaje by changing conection on the taps
10 years ago i was in a project wich i nedeed 400v three phase system\
for some european machinery
and i was able to get close to 400v

What the transformer can't do though, is to change frequency and Europe generally uses 50Hz so that would work only if the machinery was insensitive to frequency.

 

[Besoeker]

It is possible. But it might not be an acceptable solution. Much depends on whether the "machine" can be allowed to operate at an overvoltage of 9%. That is generally within the acceptable tolerances. But only the manufacturer of the machine can tell you for certain. Also, if the machine needs a neutral wire, then this proposed solution cannot work.

The transformer regulation will reduce the 9% some, so voltage possibly isn't a show-stopper. But I agree, the absence of a neutral if one is required, would be.

 

[broadgage]

220v. 3ph.? Never seen such a beast. 240 or 208 yes. I'd check the machine documents for info.

220 volt 3 phase used to be popular in parts of Europe, and some probably still exist.
Some systems were 220 volt 3 wire, 3 phase delta without a neutral.
Others were 3 phase, 4 wire, 127/220 volt, with a neutral.
A 3 phase 220 volt motor could be used on either supply.

Since most of Europe has now standardised on 230 volts, any remaining such systems would now be described as 230 volt, though I doubt that the voltage has actually been altered.

 

[Besoeker]

Since most of Europe has now standardised on 230 volts, any remaining such systems would now be described as 230 volt, though I doubt that the voltage has actually been altered.

Probably so.
I think it was just a bit of beaurocratic bit of juggling. As I recall, tolerances were changed also to make the different voltages alowable under the same "harmonised" standards.
A bit like the new harmonised wire colours.
And for what benefit? Madness.....