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Help with Transformer

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vertexdr

New Member
hello
I have a transformer with a power (Input: 230 VAC Output: 42 VAC, 6 A)
I want to reduce the power to 20VAC or 20VDC
please help
 
hi,
If you can access the secondary winding, usually the outer winding of an 'EI' type transformer, it should be possible to remove some turns from the secondary winding.

At 6A, the wire will be thick, so easy to handle.

Remove 10 turns, measure the voltage, this will give you a rough guide how many turns/volt.
When you know the turns/volt you can calculate how many turns you need to remove for 20Vac.

Its best if you measure the secondary voltage when the transformer is loaded, say about 1Amp.

Always under estimate the turns that need to be removed, you can always easily fine tune the output down by removing an odd turn or two.
 
What you have is what you have. Short of hacking the transformer there is no way to reduce the output voltage. You can add a 2:1 transformer which should be common. Take a 230/240 VAC to 115/120 transformer and use it to drive the transformer you have. That or take the 42 VAC out and drive a 2:1 ratio transformer. The first method requiring a more conventional lower current rated transformer. Another option is to rectify the 42 volts and then regulate it down which is not a great way to go. The best solution would be to get a transformer designed for what you want to do.

Ron
 
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If you can get a 20VDC output SMPS it might be happy running from a 42VAC supply.
 
Reloadron
I need this transformer for charge battery 12V 7ah using charger PS100

Does it have dual primarys?
i think not



Filament transformer (15123) Id-No. 00.15123.242000
to power the heating pf precipitation sensors
(1507 H), (1509 H), (1518 H3), (15188 H)

Input: 230 VAC
Output: 42 VAC, 6 A, 250 VA
Housing/ Weight: polycarbonate-housing · RAL 7035 (light-grey)
241 x 194 x 107 mm · IP 55 · 6.0 kg
Cable entrances 2x PG 11 · 1x PG 13.5

**broken link removed**
 

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hi vert,
Its a nice looking transformer, but the bottom line its not suitable for your application.

By the time you have built a suitable rectifier/smoothing/step down and regulation circuit it will have cost you more than to buy an off the shelf 12V SLA charger.

Also if you built such a charger, using linear techniques it would very inefficient, ~75% wasted as heat.
 
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Take Eric's advise. Also, a 12 volt SLA battery is not charged with 12 volts but closer to 14 volts. You can also charge using 500 mA and don't need 6 amps as long as you have a little time. Twelve volt small SLA chargers can be had very i9nexpensive. I have seen them for $10 USD.

Ron
 
cant he use a voltage divider? What if he got a 42V transformer to power up several equipments eg.an amplifier(it contains, preamp,power amp,etc)that needs different voltages to different circuits.eg.18V to preamp,35V to power amp..etc then must he buy different kinds of transformers for each circuits?!! Just a doubt.
 
cant he use a voltage divider? What if he got a 42V transformer to power up several equipments eg.an amplifier(it contains, preamp,power amp,etc)that needs different voltages to different circuits.eg.18V to preamp,35V to power amp..etc then must he buy different kinds of transformers for each circuits?!! Just a doubt.
If you are interested in efficiency then you can buy different transformers, or alternately use switching-type regulators to get the different voltages.

In this case, for a battery charger, a switching regulator is rather expensive for the task, and a simple linear regulator (is that what you mean by voltage divider?) would waste a lot of power. So the best thing here is to get a transformer that has the proper output voltage.
 
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