Step Down Transformer (Foysal1271)

Thread Starter


Joined Feb 22, 2016
Hay guys I need yours help. I want built a step dawon 12-0-12, 10 amps transformer. But problem is I don't know the formula. So any buddy can be help me


Joined Nov 4, 2013
The simplest way would be to get an already made off the shelf unit from an old 12 volt automotive battery charger.

The vast majority of them are designed around a simple 12 - 0 - 12 secondary winding.


Joined Jul 18, 2013
For modifying your best bet is a Toroidal of the required Va, they are very simple to wind a secondary on if you have one with one with a primary suitable for your local power.
You can find the Turns/v from a secondary already present.


Joined Nov 30, 2010
This job is a gigantic PIB. You have to start with the qualities of the core material, figure how many pounds of core you need for the watts, the number of turns in the primary for your local voltage, allowing for the power line to be +/- 5%, then the secondary turns allowing for efficiency losses in the core, and wire gauge. It takes a lot more than one formula to do all this. Do you even know where to buy the core? I don't.

Either get a transformer made for this job or at least get a core that has the right primary on it.