qsiguy said:
Ok, so if I have a transformer that has a primary of 120V and a secondary of 24V that transformer has a turns ratio of 5:1, correct? If I feed 120V into the secondary then I'll get 600V at the primary. Am I calculating this correctly?
Sorry to keep asking basically the same question. This question came up at work where one of my field techs was told to wire up a transformer that showed 220/110 for primary and 24 for the secondary and another one of my techs told him he could feed 110V and get 220 out but I told him I don't think he as the right transformer. He didn't have many details on the transformer he was trying so his info was a little vague.
Whilst your calculations are correct in a theoretical sense, in practice the transformer would saturate, blowing your input fuse. If you want to run a transformer at a higher than rated voltage, then you need to increase the frequency too - by the same percentage. So if this is a 50Hz transformer then you would need 250Hz
Also when you run a transformer backwards, you do not get the correct volts out of the primary, because of regulation.
The classic educational models of transformers say things like "a 240V tx with 2400 turns on the primary has 120 turns on the secondary, what is the output?" and the answer is of course 12V.
But that isn't a 12V transformer, unless you specifiy your open circuit volts.
In reality a 12V transformer could have 150turns, making it appear to be a 15V transformer, but when loaded up, the voltage drops (mainly due to resistance) to 12V. It's called regulation, and most transformer specs wil list it.
so take that same transformer and apply 12v to the secondary
12/150x2400 = 192V and that is open circuit. load it up, and it will probably drop to 150 or so.
i am not saying you cannot run a transformer backwards, you can. But you need to know the specs of the transformer, in particular the regulation.
for a 12v to 230 step up, one with a 9v secondary MAY be a better bet.