# Boosting transformer current output

Discussion in 'General Electronics Discussion' started by remzy, May 24, 2017.

1. ### remzy

47
1
Jun 12, 2015
As you've already read from the thread title, i need a way to get more current on the transformer output. I need to run a 24V fan for a certain aplication. I've only managed to find one transformer from my junk pile which fits the bill, but it has way too low current output. The voltage drops about 10v when i connect the fan to it. Is there a way to get more current from transformer output withouth sacrifising the voltage? The output of this transformer is about 32 volts after rectification. I'm using LM317 as a voltage regulator, but still the question is the same: is there a way to get more current on secondary coil?

2. ### davennModerator

13,984
2,015
Sep 5, 2009
thicker wire turns ( ie. a larger wire gauge)

3. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
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Jan 21, 2010
Sure, get another transformer rated for the required current.

4. ### remzy

47
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Jun 12, 2015
Yea I could do that but that would be the easy way out

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Well, another method is to unwind the secondary, counting the number of windings,

then unwind the primary, counting the windings,

Now pick a larger size wire for each, capable of carrying the larger current (i.e. twice the cross sectional area for twice the current)

Now take a look at the core. You'll have to get a core which is also larger in proportion to the current.

Then rewind the primary with thicker wire,

And rewind the secondary with thicker wire.

Then you have simply and easily made the transformer capable of more current.

All joking aside, what is the rating of the transformer, and what current do you require to operate the fan. If the transformer is suitably rated, using a switchmode regulator to convert 32V to 24V will give you a little more current than using a linear regulator. However, if you are grossly overloading the transformer, nothing will help.

6. ### remzy

47
1
Jun 12, 2015
Its a tiny fan. It uses about 200mA. Even when I connect the fan directly at 32 volts after the rectifier, the voltage drops to about 20V when the fan is on.

7. ### Minder

3,213
700
Apr 24, 2015
You cannot exceed the Va rating of the transformer, regardless of winding gauge.
This is dependent largely on core size.
M.

8. ### duke37

5,364
772
Jan 9, 2011
A transformer for double the current (power) will be about double the weight.
What is the LM317 for? A fan should work even on unsmoothed rectified AC.

9. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
I think we need to see the circuit. Something sounds fishy

10. ### remzy

47
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Jun 12, 2015
So that I can adjust the speed of it

11. ### remzy

47
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Jun 12, 2015
It's the most basic LM317 circuit. It's not the circuit's problem but the transformer is apparently too weak.

12. ### BobK

7,682
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Jan 5, 2010
If you can't supply the specs of the transformer, at least tell use how large it is. A pic with a ruler would be good.

Bob

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13. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Or problems may be due to how you rectify and filter the AC.

These questions are answered by a good schematic.

If you don't want to help us by answering our questions, then I'll go back to my first answer, get a bigger transformer.

Don't tell anyone I said so, but I might even go so far as to suggest you get yourself a thronomister because it's the only way I know to boost current without affecting voltage.

remzy likes this.