Adding Extra Windings to a Transformer

[Dennis]

If I were to add some extra secondary windings to a 12V 160VA Toroidal
transformer to increase voltage, assuming I use the correct wire and
all, would it increase the VA that the transformer uses or would the
VA stay the same and then give me less usable amps?

I've found that under a high constant load, the voltage drops a bit
too much. Instead of buying a 15V transformer and then having to drop
the voltage with a resistor, I would like to add a couple of extra
windings to give me the extra couple of volts I need. But I still need
close to the 160VA that the transformer puts out, so I don't want to
drop that figure if possible.

Thanks for any input
Dennis

 

[Bushy]

Depends on whether the thickness of the primary winding wire is the limiting
factor. Or the heat that the transformer produces melts the insulation.

Extra winding are common practice and can be good.

Peter

 

[John Crighton]

On 21 Jul 2003 17:43:28 -0700, white_dennis@yahoo.com (Dennis) wrote:

If I were to add some extra secondary windings to a 12V 160VA Toroidal
transformer to increase voltage, assuming I use the correct wire and
all, would it increase the VA that the transformer uses or would the
VA stay the same and then give me less usable amps?

I've found that under a high constant load, the voltage drops a bit
too much. Instead of buying a 15V transformer and then having to drop
the voltage with a resistor, I would like to add a couple of extra
windings to give me the extra couple of volts I need. But I still need
close to the 160VA that the transformer puts out, so I don't want to
drop that figure if possible.

Thanks for any input
Dennis

Hello Dennis,
just for fun, wind on say 10 turns of hook up wire
that you have lying around. With the transformer
load removed from the other secondary winding
measure the voltage from your new 10 turn winding.
From that, you now know the turns per volt ratio.
Wind on enough wire to give the required extra
2 volts that you need when you put the two windings
in series. Start Finish Start Finish.

If your transformer under load becomes too hot because
you have exceeded the VA rating too much, that's a bummer,
you will have to buy a transformer with a higher VA rating.

If "Buy" is a dirty word for you as it is for me. You may be
able to find another smaller transformer and wind a suitable
2 Volt secondary winding on it, then connect the secondary
windings of two transformers in series. I was thinking of a
small transformer with primary and secondary side by side
on a plastic bobbin. Cut off the old secondary winding.
With an assistant, you could easily thread on a few dozen
turns by hand. You doing the holding and guiding of the
wire and your assistant doing the pulling through and
walking to and fro.

Have Fun
John Crighton
Hornsby

 

[Mainlander]

In article <3e63cd14.0307211643.39721b0d@posting.google.com>,
white_dennis@yahoo.com says...

If I were to add some extra secondary windings to a 12V 160VA Toroidal
transformer to increase voltage, assuming I use the correct wire and
all, would it increase the VA that the transformer uses or would the
VA stay the same and then give me less usable amps?

The issue will be the maximum primary current as well, so I think the VA
rating could be the same as before.

I've found that under a high constant load, the voltage drops a bit
too much. Instead of buying a 15V transformer and then having to drop
the voltage with a resistor, I would like to add a couple of extra
windings to give me the extra couple of volts I need. But I still need
close to the 160VA that the transformer puts out, so I don't want to
drop that figure if possible.

Voltage variation is a fact of life and that's why power supply
regulation is used if it is important to get a reasonably constant
voltage. this need not be a three terminal regulator with its associated
voltage drop and consequent high power dissipation.