Homemade Transformer?


Moved over to the UK from the US a couple of months ago and my fiancee has brought with her a 110V tea-steeper with her.  Apparently it possesses magical properties that cannot be reproduced by other local appliances.  

It will blow out the fuse in a 500-watt transformer, which is the largest that I have.  My question is, why are these things so expensive?  I have very limited knowledge about them, but from what I do know they don't seem that complex.  Some of the higher wattage transformers are the same price as a netbook computer!  What is in them that costs so much?

Also, can you make your own?  



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Kiteman7 years ago
Why will a simple travel-adapter not do the job?

Randomly googled example.
knightop (author)  Kiteman7 years ago
This was a gift from someone...I was afraid to push 220 through a 110 appliance.  I know there are some electronics in the steeper, plus I'm assuming the heating element is designed to work with 110.

I haven't opened it up, so couldn't really say for sure what going on inside there, but didn't want to burn it up.

There are adaptors that aren't just wires connecting pins, but actually deal with changing the voltage.  A Google or Amazon (or whatever the UK equivalent is) search ought to turn something up for about US$20.
knightop (author)  kelseymh7 years ago
I have a bunch of different step down transformers that will take 220 down to 110 but they will only handle so much wattage.  The cheaper transformers are usually around 100 watts and won't hold the heating element in the steeper. 
How big is this tea-kettle, anyway?  I thought those things ran just a few hundred watts, but you said you were blowing a half-kW.
knightop (author)  kelseymh7 years ago
It says 10amps on the plug...but I'm sure that is over rated for their liability.   I have no idea why this thing pulls so much.  Could be the transformer itself, they do have lifespans and after so much use it might just blow a fuse under any decent load. 

Which raises another question.  If it is a 500 watt transformer, to calculate the amperage created to burn the fuse do I divide into 110 or 220?

Okay so that is 10 amps at 110volt which would be 5amps at 220volts
Wattage is 10x110 = 1100watts ( or 5x220=1100watts ) so, to be safe, your transformer would need to be a 1500watt unit.
Kettles here are usually between about 1000 and 2000watts and I guess it is the same in US of A.
The UK equivalents are "Google" and "Amazon"...
Go to RS or Maplin and they should be able to hook you up with an appropriate transformer.  It may not be very cheap, though; which you have apparently learned already.

Why are they expensive?  It takes a lot of copper wire, for one, and a lot of laminated steel for the cores, and because you're dealing with primitive 50 Hz AC, there's no short cuts.  There may be cheaper imported-from-China models available, possibly from stores or market stalls that deal in imported electronics parts or that cater to immigrants.

Transformers are not rocket surgery to design or rewind.  The old ARRL radio amateur handbook had a useful section that covered the basics; so did the "Electricity 11" course I took in high school.  Microwave ovens have high power transformers in them and dead ones are readily available, but they go from 120 or 240 to several thousand volts.  If you found a dual voltage oven, it may be possible to use the transformer as an autotransformer.  If not, remove the old high voltage winding, ideally measuring the output first then counting the turns as they are removed.  This requires a voltmeter that can handle the high voltage, and obviously great care not to electrify oneself.  And then patience and care unwinding the coil, since there may be thousands of turns.  It may be impractical.   So, maybe just remove the primary (240 volt) winding from a second microwave oven transformer, measure out roughly half the length, and wind that onto the secondary of the first transformer.  Measure the output and add or remove turns to get it to 110 to 120V.

You could also ignore the secondary winding altogether, and just turn the primary into an autotransformer by adding a center tap.  Scrapped MIG welders or battery chargers may also be suitable transformer donors.

It may be worth checking with local transformer manufacturers.  Smaller outfits will make custom coils, and it's possible they've ended up with surplus from overproduction, prototypes or returns.  Or they may have something that'll work as an autotransformer.

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