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Rewind a Power Transformer

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Mosfet

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Hello everyone,
I want to rewind a large iron/steel transformer.
It has 'E I' plates that measure 5.5 x 4.5 x 2.5 inches.
It has a 4 to 1 ratio [2" - 0.5"] spacing on the "E".
The old windings are coated copper ribbon 1/16 inch thick,
essentially solid copper bar with no resistance.
I want 50 v - 0 - 50 v [100v center tapped] on a 120vac primary.
What wire size and turns-length would I need?
Thank you kindly.

This very simplyfied formula work for me about 20 years...
The iron core carry about 870VA (A=29.5qcm)
Turns of primary 155 (1/16inch, enough for 7.5A)
Turns of secondary 2x71 (center tapped) 1/16 inch

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• trafo.GIF
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Thank you Sebi,
I am painting my house and cannot find any of my electronics books.
A search on the internet gave me too much information.
I hate to throw away such a large transformer
Your experience was just what I needed.
Dave [mosfet]

After many calculations I determined my transformer core was not suitable for rewinding at the voltage/amperage levels wanted. ['A' was too small]

I also found a great program that makes this process much easier:

Transformer design

Thanks rebottex,

The core [or "A" in Sebi's diagram] is 1.125 x 2.625 inches.

My calculations give me about 350 watts to work with.

Too little for the 100 volt AC center tapped 6 amp windings I wanted.

I could get 80vac CT at 3.8 A or 76vac CT at 4 A.

I think the original purpose was spot welding 10 volts at 30+ amps.

mosfet,

try this formula. i'm using this for almost 10 years.

Example: Core Size = 1 ¼ X ¾

Formula 1:
Convert first into decimal:
thickness X center tapped = Core Area

1.25 X .75 = 0.9375 (Core Area)

Formula 2:
Compute power watts:
Power=Core Area (5.58 ) 2

0.9375 (5.58 ) =(5.23125) 2
Power =27.365977 Watts

Formula 3:
Compute number of turns:
Turn / Volts = 5.775 / Core Area

5.775 / 0.9375 = 6.16 Turn over volts

Primary winding:
6.16 X 220 Volts = 1,355 Turns

Secondary winding:
6.16 X 6 Volts = 37 + 37 turns for full wave design
6.16 X 6 volts = 37 turns for haft ware design

Formula 4:
Compute for Primary & Secondary Current:
Current = Power / Volts (I= P/V)

For primary current:
I = 27.365977 / 220 Volts = 0.124308 Amp.

For secondary current:
I = 27.365977 / 6 Volts = 4.5609962 Amp. For haft wave design
I = 27.365977 / 6 Volts = 4.5609962 / 2 = 2.2804981 Amp. For full wave design

Formula 5:
Compute for Circular Miles AWG:

Current X 680 or 700 recommended 680 for normal heat

For primary winding:
0.124308 (680) = 84.59 Cir. Mil.
AWG # = 31
(Please refer the nearest value to AWG standard table)

For secondary winding:
2.2804981 (680) = 1551 Cir. Mil.
AWG # = 18
(Please refer the nearest value to AWG standard table)

You have now designed:

220 volts primary
6 volts full wave secondary
2 Amps.
27 Watts

Formula 2:
Compute power watts:
Power=Core Area (5.58 ) 2
where it came from? (5.58)2Formula 3:

Compute number of turns:
Turn / Volts = 5.775 / Core Area
where it came from 5.775

formula to rewind ferrite power transformer

Hi.
i want to wind center taped ferrite core transformer. my requirement is 12-0-12vac and out put 220vac.kind tell me formula i.e no. of turns for primery winding,no. of turns for seconday winding. area of core and thickness of wire to be used.

It sounds like you want to run this transformer at 50/60Hz?

Ferrite isn't suitable for low frequency operation, you should use laminated iron at power line frequencies.

Hi
Please send formula to built up a step uptransformer center taped 12-0-12 out put 220 for inverter. please send formula :
no. primary turns
no. of secondary turns
core area

Fakeeeeeeeee

Thats all the bulshit above, never ever transformer will work on these configurations or calculation.The turn ratio was totally wrong.Attaching a excel sheet for calculation but let me tell you a thing it is 80 % correct OK.

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• transformers.zip
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