Inverting a 220 to 110 v transformer

[elogicca]

Has anyone reversed a 220 to 110 step down transformer send in 110v and get out 55v ? is this pratical it's a 1000va transformer so could i get 55v 20amp out of it this way?

[Al_The_Man]

You won't by reversing it, if you use the 110 as primary you will get 220v out, if you put 110v into the 220 primary you will get 55v out but the winding is probabally not gauged for 20amps, and your VA will be reduced.
Al.

[sch]

To elaborate on Al's reply: the primary of a 110v 1kva transformer will have wire and core rated at 9-10amps conservatively and the 220v secondary will have wire rated for 4.5-5amps. You can't change the wire amp capacity, though the voltage can range around the 2:1 ratio upto the limit on the insulation, which would be in the 400-500vac range. Ie you could use it to
change 220 to 440vac but it would be imprudent to go higher and the VA would be reduced proportionately. The wire and core will overheat if the wire amperage rating is exceeded. Running the transformer as a 110 to 55vac
with higher voltage wire at 4.5-5amps and lower voltage at 9-10amps reduces the VA rating to 500.

[elogicca]

A friend will be dropping off the transformer today, it was removed from some machinery i will have the specs...

As per inverting yes i know i posted wrong I was gonna feed 110 into the 220 coil to get 55v out.

[gar]

070120-1144 EST USA

sch:

The limitation on the maximum input voltage to a transformer is not usually the insulation breakdown voltage, but rather magnetic saturation and the resulting high magnetizing current which causes the transformer to burn out.

elogicca:

If a transformer is rated 120 V 60 Hz on a particular coil you should probably stay below 130 V 60 Hz. It depends upon the transformer design.

If you lower the frequency to 50 Hz, then the nominal rating for the above should be 5/6 of 120 or 100 V.

You can always use any transformer at any lower input voltage than its rating at its rated frequency.

.