Do transformers (110V-220V) drain much power?

Question

Hello everyone

I have a 110V hardware plugged in at home (we use 220V) by way of a step down transformer and I was wondering if transformers 'use' more power than usual. I don't want a nasty electircal bill.

Because even when the hardware is 'off', the transformer itself is still on. It still hums. I am wondering if the transformer is constantly pulling power out of the wall socket 24/7 if I leave it on.

Any help will be greatly appreciated. Thanks all.

Answer 1

A transformer like one you are using is called a step-down transformer because it is changing the source voltage 220vac to 110vac. The answer is yes; it will draw current even though you have no load on the secondary side. This is because the coil on the source side (primary) has a constant current flowing through it; it is a closed loop circuit. The secondary winding(s) produce current flow through electromagnetic inductance by their close proximity to the primary coil. Your rate of current will not be as high if you have a closed circuit on the secondary but current will continue to flow unless you open the circuit on the primary side. I bet that not only does it hum (magnetic field) but it is also warm to the touch. Heat equals energy loss and the energy must be coming for someplace.

Answer 2

Mike, here is an easy approximation with no tech talk you can perform. Leave the power on to the transformer but remove the load and let temp stabilize. Feel how hot or better yet put a thermometer on the transformer. This heat is a direct result of transformer losses while idle.
Next remove power to the transformer and devise a metal box to put a lamp in to heat the transformer overnight. Try to capture all of the lamp heat into the transformer to heat the core. Try this using various lamp wattages. When the temperature rise from the lamp equals the temperature rise from running the transformer idle the lamp wattage will be a close estimate of the power wasted by the transformer at idle.
A wattmeter will also tell you this but they can be expensive. A good meter and an oscilloscope will be necessary otherwise but that is another story.
Heat is always wasted energy the more produced the more it costs you to run.
Regarding if you should let it run the answer is sure why not. You probably already have transformers running in your house all of the time. Door bell, Furnace, hot water tank, may be a few.

Answer 3

Thanks everyone for your answers. (I am using another acconunt)

What I am asking in a nutshell, is basically will I be drawing so much power that I will get a $1000 + bill a month if I simply leave the transformer plugged in the wall.

And I think I get it now, but there is still some tech talk I don't really understand. By the way, it is a 110V hardware, and I am living in a 220V country.

So what you guys are saying is that there is still a NO LOAD loss, which means that the transformer is still using power even though my DVD player is not on.

Is there any concern that the transformer would fry and malfunction if I leave it on say... for 2 weeks plugged in. Note I am not leaving the DVD ON for 2 weeks, just the transformer. The DVD is off. I mean, there is still a red light next to the power sign on the player, as with most electronics, it is actually on stand by. Thanks.

Answer 4

No transformer is 100% efficient, so the power use will be higher. However, most tranformers are pretty good, I would say over 80% efficiency, so at the most you would use 1.2x the normal power. The tranformer does take power even if the load is off. If it hums and gets warm, that is an indication of power being used. Again, that wil also be much less than the operating power, but unless you can find the manufacturer's detailed specs, it is not possible to know how much that is. In general, if you do not expect to use the equipment for a long period (a day or more), it is a good idea to unplug it.

NOTE: There are devices you can get which will measure the power being drawn; that is the only way to get an accurate indication. It's probably not worth it to buy one of these unless the transformer is very large and can draw a lot of power when unloaded.

Here is an example of such a device (but you would need a 220v model). http://www.smarthome.com/nav/ProductResults.aspx?Ntt=power+meter&Ntk=All&Nty=1&Ntx=mode%2Bmatchpartial&N=0&x=4&y=10

Answer 5

There are 2 considerations here, they are called load losses and no-load losses.

The load losses are directly related to the impedance of the transformer and the current flowing through the transformer. I would estimate that the load losses would be approximately 10% unless you have a really cheap transformer. That is simply the price you pay for transforming voltage. You will always have load losses. The transformer manufacturer can reduce these losses by using larger conductors inside the transformer.

The second is called no-load losses and these are the losses that will occur even when no load is connected and no current is flowing. These losses can also not be avoided completely. However, you can build transformers to reduce no-load losses by using either more core-steel or higher grade core-steel. These losses are related to the magnetic fields generated inside the transformer. I can't predict the exact value of no-load losses but I would assume that it would normally be less than 5%, again assuming it is not made extremely poorly. So if you had a transformer rated at 500 watts, I would estimate that you would have less than 25 watts of no-load losses.
So, as the person said in one of the other answers, I wouldn't worry about unplugging it every time I stopped using it, but I wouldn't leave it plugged in for days on end either.

Answer 6

That's an industrial UPS to be rated for 12 amps. It can power a couple entire rooms in a house, including the lights. To echo what everyone else has said; you do NOT want a tiny little consumer transformer to adapt 220v to 110v. You'll need an industrial-grade transformer to match your UPS.

Answer 7

Normally the "no load" current is fairly low so wouldn't be a problem, however the only way to know for sure is measure it since no-one on here knows anything about the transformer you have.

A rough way to check it is turn everything else off in the house, see the meter has stopped rotating, then plug in your transformer and see if the disc turns (the meter will say on it how many turns = 1kwh).

A multi-meter would also work just to see what "no load" current is on the thing.

your safety concern depends on what you have. if its a "home made' thing then you take the associated risks, if its not modified from how you bought it then it will be covered by the safety guidelines of the place you bought it.

Answer 8

110v To 220v Transformer

Answer 9

220v To 110v Transformer

Answer 10

I'm a electrician,but I'm not getting the ? you re trying to ask,yes it still draws current but not much if you haven't any load in amp draw,use the ohms law formula to see how much it will cost monthly,electricity is sold to customers in kilowatts.