Electronic – How do step-up transformers work


I’m trying to figure out how a step-up transformer works. A step-down transformer is simple and logical enough; you start out with a higher voltage and end with less, the remainder being wasted as heat. But with a step-up transformer, you end up with more voltage than you start with.

I tried looking it up, but all I can find (whether online or even in some electronics texts) is general information on how transformers work (induction, Faraday’s law, construction, etc.) and explanations of the difference between step-ups and step-downs in terms of the number of turns, but not specifically how step-ups result in more voltage.

Where does that extra voltage come from? Not magic…

Best Answer

I think what you're missing is the current...

  • Step down transformers change a high voltage/low current, to low voltage/high current.

  • Step up transformers change a low voltage/high current, to high voltage/low current.

So, in an ideal 100% efficient transformer, the power doesn't change and no heat will be generated by the transformer, i.e. the power in = the power out, because Power = Volts x Amps.