# transformers

Discussion in 'The Projects Forum' started by kumarm, Nov 30, 2013.

1. ### kumarm Thread Starter New Member

Nov 30, 2013
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0
i am trying to modify an existing tranformer for chargig my inverter batteries

i got the tranformer from an existing voltage stabilizer with

input 140-240 volts

and output as upto 300 volts and 250 watts

i ripped of the secondary coil ,it has a metal sheet core
consider there are 50 turns in primary coil (assuming as i dont want to unwind primary also )

to get 20 volt 15 amp output how many turns should i have in secondary

the power input in my house is 240 volts and 5 amp

my inverter battery is 12 volt 42 ah i guess 20 volt and 15 amps will be enough to charge the battery soon enough

or

i can i rip the primary too and start the windings from scratch ?

Jul 18, 2013
10,851
2,522
Put on 10 turns and measure to establish how many turns/volt, a typical number is 2-4T/V.
Wind the final secondary with gauge sufficient for 15A.
You have a 240v service that is rated for 5amps only?
There is no need to rewind the primary.
If you re-install the metal shield between pri & sec, make sure you do not make contact with each end, as it will produce a shorted turn.
Max.

Last edited: Nov 30, 2013
3. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,155
772
I recon 4 or 5 turns will give you 20v if your primary is 50 turns.

4. ### kumarm Thread Starter New Member

Nov 30, 2013
4
0
You have a 240v service that is rated for 5amps only?

yes 240 with 5 amps only

now i can get the volts needed but ampere is still low

8 turns in secondary 18-19 volt and 7-8 amps only how to increase ampere output

Jul 18, 2013
10,851
2,522
If you have a supply (transformer) rated for 1200va (240vx5a) then the secondary current will be inversely proportional, 1200/18 = 66amps.
The secondary conductor sizing would be be capable of carrying this current.
Max.

6. ### kumarm Thread Starter New Member

Nov 30, 2013
4
0
can i use single core copper wire instead of waxed coil

in case of wire will the use of multi core copper wire increase the output in away

more like using a bunch of copper coil connected parallely instead of 1 thick coil of copper

Jul 18, 2013
10,851
2,522
You can used a stranded conductor if you wish, but it is does not make for a compact or neat winding.
The normal is single strand copper conductor enamel coated, motor winding or magnet wire.
Max.

8. ### kumarm Thread Starter New Member

Nov 30, 2013
4
0
thank you i got the require output from transformer and battery is charged

can u guys suggest a simple and easy inverter circuit ...

sorry if i am asking too much i am basically a mechanical engineer so NIL knowledge on electrical circuits but had to do this project to power up my machine with very customized voltage output and i couldnt get it in market

i need an inverter circuit to get 2 hours of 5amp current at 240 volts from 42ah battery