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# Transformers?

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#### andy257

##### Member
Hi Guys

I need a transformer which is capable of transforming 12V into 240V ac.

However the 12V side must be cabable of delivering 10A. Preferably without a centre tap.

I know what i need but when looking on rs, maplins etc i am bamboozled.

They give specs quoted in VA (volt amperes i think) is that power as in Watts?

its prob right there in front of my face which one i need but i cant figure it out. Also they say on the output side 2 * 6V or 2 * 12V etc ......

does that mean there are two terminals with 12V (one negative and one positive for ac?) does that therefore have a centre tap cos there is two of them?

i am totally stuck with all these specs, i know what i need but can figure out which one suits my needs.

can anyone shine some light on this for me

cheers
andy

Don't let the presence of a center tap stop you from using an otherwise suitable transformer. The tap can simply be clipped off close and taped or heat-shink sealed.

Transformers are normally rated in VA which is roughly the AC equivalent of a wattage rating.

You said:
I need a transformer which is capable of transforming 12V into 240V ac.

However the 12V side must be cabable of delivering 10A. Preferably without a centre tap.

That's a little bit confusing -- if the 12V side is the primary, then it won't be "delivering" 10 amps...

As a general rule of thumb, a voltage step-up across a transformer produces a similar step-down in current, and vice-versa. If you need to raise 12VAC to 240VAC, you need a step-up of 20:1 (12 x 20 = 240). If desired current output is 10A, this transformer would need to be able to handle 200A on its primary side! On the other hand, if the 10A is your projected input current, you are only talking about 500mA at the secondaries...

So... where does the 10A requirement come in?

Or... are you trying to drop a 240VAC input to a 10A @ 12VAC output?

Give us a little better info if you want some more help.

Hi,

i need to use a transformer in a project to turn 12V into 240. Its an inverter circuit. I wish for a maximum power output of about 100Watts

100/12 = 8.33Amps i need a 10 amp secondary winding which i will swap over and use as the primary. Iam just gonna connect the transformer the other way around and use it as a step up instead of down.

hope that clears something up , thanks for your help

OK -- in that case, the Hammond 266P24 should work though the 266PA24 might be better -- higher VA rating; more room for error.

These are dual primary/dual secondary transformers, rated at 120VAC/240VAC primary and 12V/10A - 24V/5A (266P24) and 12V/12A - 24V/6A (266PA24) secondary. As to connecting this baby up, simply take each pair of windings in series -- see diagram below: