How to wind a transformer

[MaXiZ]

Hi to all i knowt that my question may appera asreally stupid but it's not for me!
Ok my question is:
What's the correct way to wind a transformer?
Secondary2-Primary2-Secondary1-Primary1-Core-Primary1-Seccondary1-Primary2-Secondary2

Secondary2/1-Primary2/1-Core-Primary2/1-Secondary2/1
(in this case i mean that the primary are winded on the core in the same sense... Start to winding, center tap, continue do winding, end. This for primary and secondary)

[leroy]

It depends on what the transformer is used for (welding transformer, power transformer, audio transformer)

I won't recommend winding a power transformer yourself since this can lead to dangerous situations. Isolation material, -thickness and distances must be respected!

Please specify for what purpose the transformer is needed.

[MaXiZ]

It will be used on a Push Pull SMPS for a car amp.

[leroy]

I think it was in the Elektor magazine about a decade ago where a car-booster amp was detailed out, together with transformer winding instructions. See if you can get one of those magazines.

For SMPS transformers it is important to get good coupling between primary and secondary together with low stray inductance. This is achieved best with a so called 'sandwich' configuration. In case of a car booster amp the primary (low voltage-high current) would probably be a copper foil winding or thick litze-wire. In my opinion the half secondary - primary - half secondary is the best solution for this.

I recommend to search for SMPS transformer winding literature to be sure about this.

Good luck!

[MaXiZ]

the half secondary - primary - half secondary

Probably u're refferign to this..
Secondary2/1-Primary2/1-Core-Primary2/1-Secondary2/1
But this mean...
SECONDARY WINDING1-CENTER TAP-SECONDARY WINDING2
PRIMARY WINDING 1 -CENTER TAP-PRIMARY WINDING 2
C O R E
C O R E
C O R E
PRIMARY WINDING 1 - -PRIMARY WINDING 2
SECONDARY WINDING1- -SECONDARY WINDING2
Is it clear?
Do u mean this?

[MaXiZ]

no one can/want give me an help?

[leroy]

I don't understand why you use center tapped primary winding. There's only 12Vdc plus and neutral available (on board voltage) so the SMPS converter topology will probably be a full bridge, right?
The secondary winding will be center tapped to get output voltage plus-neutral-minus. I think it is possible to use the connection between the two secondary coils as center tap. Let me try to put this out:

secondary secondary secondary
=======================
primary primary primary primary
=======================
secondary secondary secondary
=======================
core core core core core core core
core core core core core core core

[soren]

I assume you want centertapped primary because of use of push-pull primary topology (which is quite convinient with 12V supply voltage)?

What about:

Second sekundary
=============
Sekond primary

First primary
=============
First Sekundary

CORE CORE CORE

= is isolation between vindings if mains isolation is required (3*0.1 mm mylar foil), but for use in a carstereo it might be left out.

Arrange the windings in such a way that the two "First" windings will be used together. This will reduce leakage inductance, which is quite bad for SMPS design.

You could also use a single secondary and a bridge rectifier, much simpler transformer, and better performance from this, but an extra diode drop on the sec.

By the way, wouldn't +/- 10V output voltage from an amplifier be far sufficiant in a car? This you can get just with a full bridge on the car's 12V. Personally I would get a headacke and loose my attention to driving if I fired off a 100W+ amp in a car...

[MaXiZ]

Infact i'm using a push-pull topology and i need around +/-45V@5A. So soren u suggest to wind the two primary and make them center tapped and then only one secondary? Is the same thing as two secondary center tapped?

[soren]

Originally posted by MaXiZ
Infact i'm using a push-pull topology and i need around +/-45V@5A. So soren u suggest to wind the two primary and make them center tapped and then only one secondary? Is the same thing as two secondary center tapped?

Well, I was thinking about a full-bridge amplifier topology (which definately is to be considerede over half bridge topology at high output powers, at least for switching amps). Since you need +/- 45V, you do have to have a centertapped secondary.

Please pay attention to the issue of supply pumping, if you are making a half bridge switching amp, it makes the control circuitry a bit more complicated.

The amplifier you want to use, is it a linear or a switching amp?