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zilog 21st December 2005 10:43 PM

smps transformer winding
 
I am about to start winding the bobin for my smps transformer. The transformer is an ETD49 (I had one already), that will have double primary center-tapped windings of 3 turns, 8 wire 0.7mm litzed each. My problem is that I want each of the primaries to go from one side of the bobin to the other, but with this wire I will only cover half of the length with each primary, what do you recommend me to do? Should I wind both primaries in series and take the tap in the middle and route it out to the edge of the bobin?

Additionally, there will be a double, centre tapped secondary side with 2x15, double litz-wired 0.7mm. This wont fill an integer layer either (you can squeeze ~45 turns on each layer), how is this best spread over the bobin?

mzzj 21st December 2005 11:25 PM

Re: smps transformer winding
 
Quote:

Originally posted by zilog
I am about to start winding the bobin for my smps transformer. The transformer is an ETD49 (I had one already), that will have double primary center-tapped windings of 3 turns, 8 wire 0.7mm litzed each. My problem is that I want each of the primaries to go from one side of the bobin to the other, but with this wire I will only cover half of the length with each primary, what do you recommend me to do? Should I wind both primaries in series and take the tap in the middle and route it out to the edge of the bobin?

Additionally, there will be a double, centre tapped secondary side with 2x15, double litz-wired 0.7mm. This wont fill an integer layer either (you can squeeze ~45 turns on each layer), how is this best spread over the bobin?

How about not twisting wire bundle but keep it flat? And interleave both primaries in same layer(though it may be super-difficult to wind 16 wires parallei flat)
This would result 33 millimeter winding widht, does it fit on your bobbin?

--
And 7 wires twisted together would result more neat bundle than 8

For optimum results i would recommend copper foil for primary.

zilog 22nd December 2005 07:35 AM

I think Im pushing the limits already, what current density can be tolerated in primary windings in a push-pull 12V var amplifier topology? the plan is to power a pair of class D half-brigde amplifiers that will be able to use full rail voltage of +-45V into a load of 4 and ultimately 2 ohm at 60-65% modulation. I know that peak-to-average ratio for music is quite high, but is there any rule of thumb regarding the design? The amplifiers will probably be powering woofers.

Eva 22nd December 2005 08:21 AM

It's not a matter of current density (irrelevant) but a matter of wire dissipation. Depending on size, shape and cooling you can tolerate 3, 5 or even 7 watts per winding (numbers obtained empirically). Lower ir obviously is better.


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