How much power does a stepdown transformer use?

[HelifaxNZ]

Just wondering whether you use less power when using a step down transformer to 110v and have a 15W pump plugged into it?

[suphew]

No because your using the same amount of energy to do the same job. But it also cost you some energy to do the step down as well.

[HelifaxNZ]

I thought that might be the case. Will a stepdown transformer cope with being on 24/7?

[suphew]

Yes but its all about getting theright sized transformer. eg the mains power out on the bigger lines is 11,000v those big green boxes either on the side of the road or at the top of power poles are stepdown transformers converting it to 240v.

So the point is you just have to get a big enough transformer so that it doesn't get too hot running all day.

[HelifaxNZ]

Many thanks for your replies.

[Bluetom]

The way a transformer works is it steps down the voltage by a ratio in this case it's about 2.2, this is the turns ratio. The power in equals the power out therefore the current increase by the same amount. so if you were runnin 5A through your mains then through the pump it would be almost 11A.

Hope this helps. Power in = power out approx. (some is lost to heat though) depends how effective your trasnformer is.