transformer voltage reduction

[goodguys]

Hi And thanks for reading this thread.


Having difficulty finding a toroid transformer with the correct secondary voltage, so am wanting to mod a transformer to lower the secondary voltage. If i remove turns from the secondary winding what will this do to the voltage will it go up or down.

 

[johnego]

It will go down of course.
Primary_Voltage/Secondary_Voltage = Primary_Turn/Secondary_Turn
SV=PV*ST/PT-->Lower ST (Secondary Turns) will lower SV (Secondary voltage)



If the power line input has 220V and 240V, you can choose 240V so the output is a bit lower than if you connect to 220V. This is because the 240V has more turns than the 220V.
SV=PV*ST/PT--> Higher PT (Primary turns) will lower SV (Secondary voltage)

 

[PANN]

DOWN but,

calculate first the ratio between P/S so,
you can estimate the number of the turns need to remove,
turns / volt.
I have done it many times, difficult job because its hard to remove the first E I.
Use a thin knife and be careful dont destroy the core.

 

[johnego]

I have done it many times, difficult job because its hard to remove the first E I.
Use a thin knife and be careful dont destroy the core.

His is a toroid I believe. The secondary turns are on top of the primary turns. It should be easy unless you want to make it look good

 

[zigzagflux]

Consider a small little rectifier transformer connected as an autotransformer in bucking polarity. It will take the primary voltage (if 240) and drop it down to where you want it, perhaps 210V. Use that to feed the toroid. The transformer is really small when connected as an auto with a small step down; works great too.

 

[Mark Tillotson]

Hi And thanks for reading this thread.


Having difficulty finding a toroid transformer with the correct secondary voltage, so am wanting to mod a transformer to lower the secondary voltage. If i remove turns from the secondary winding what will this do to the voltage will it go up or down.

Or you can add extra secondaries on top and connect in opposite phase to the existing secondaries - no damage to original transformer.
You can also ensure the new windings are evenly spaced around the toroid, not possible to guarantee by removing part of an existing winding. You need to derate the VA rating for the whole transformer a little as heat conduction will slightly compromized.