Is it true that an 110v electrical device consumes 110v or 220v when it is connected to the 220v power grid?If not,tell me how to make it draw only 110v from 220v without wasting current.
closed as unclear what you're asking by PeterJ, Lorenzo Donati, Daniel Grillo, Dave Tweed♦ Aug 4 '15 at 15:18
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I'm assuming you mean AC mains here, In which case you are looking for transformer. A transformer is simply two windings on a magnetic core in your case you need one with a two to one ratio.
Luckily for you 220:110 is a common requirement and you should be able to buy one from your local builders merchant. You need to ensure it has a suitable VA rating for the application. Multiply the rated voltage of your equipment 110V by the rated current, this is the minimum VA rating needed. Buy a transformer with at least this rating. The only downsides to buying one with an even larger VA rating are it will be heavier and cost more.
I think your best bet would be to use a 220 V to 110 V step down converter & use the o/p 110 V for your devices.On the market there are a lot of converters which do this:
For example:220 V to 110 V.
This one seems to be a bit costly as it does both step up & down,i'm sure you could find a lot of only step down converters on amazon.