Years ago I started using this simplified model.
It can give an average idea of HF transformer behaviour. But transformers have their parasitic components distributed in a lot of variety, giving lots of varying by values and connections RLC small networks. Depending on the interleaving, you can mimic an overall HF behaviors with filters of different orders, resonance behaviours and the amount of resonances.
IMHO to simulate properly, each interleaved section should be treated as a separate transformer with its own parasitics and neighboring ones.
But it's still a useful sim. Especially playing around with the Cs to Ls+Ls2 ratio or even Cp/Cs to Ls+Ls2 would prevent you doing some catastrophic interleaving hence transformers for the trash bin.
It can give an average idea of HF transformer behaviour. But transformers have their parasitic components distributed in a lot of variety, giving lots of varying by values and connections RLC small networks. Depending on the interleaving, you can mimic an overall HF behaviors with filters of different orders, resonance behaviours and the amount of resonances.
IMHO to simulate properly, each interleaved section should be treated as a separate transformer with its own parasitics and neighboring ones.
But it's still a useful sim. Especially playing around with the Cs to Ls+Ls2 ratio or even Cp/Cs to Ls+Ls2 would prevent you doing some catastrophic interleaving hence transformers for the trash bin.
These things are so complicated.
May I tell a little story -
Of course
I have to say I know nothing.
May I tell a little story -
I bought a Chinese 10K-10K amorphous transformer double-C with two discrete winding stacks; it came with centre taps. But it rung extraordinarily. Still, I tested as a choke (all windings in series), no ringing, bandwidth to 150kHz! 210 Henries measured. 45 mA capability. So that way, unintended, a great anode load (10Y..). So what was wrong? couldn't find out. Put aside.
Some time ago I thought, can I use it as 10K-2K5 1/2 transformer? or in fact 2K5 to 15K (1/3) to use it as driver? So I opened the transformer winding to get to the solder patch. I took the two parts apart, and tested.
Behold, with one section (1:2. 2:1) it was beautiful, as soon as I attached the second secondary (in series with that of the other winding) it went crazy, big disparity in the bandwidth, big phase difference even at 500 Hz as I did the sweep, between the prim and the sec. winding. Loaded with some reasonable load. Is it because I did the stupid thing of going across the bobins? But 1:2 was good.
Some time ago I thought, can I use it as 10K-2K5 1/2 transformer? or in fact 2K5 to 15K (1/3) to use it as driver? So I opened the transformer winding to get to the solder patch. I took the two parts apart, and tested.
Behold, with one section (1:2. 2:1) it was beautiful, as soon as I attached the second secondary (in series with that of the other winding) it went crazy, big disparity in the bandwidth, big phase difference even at 500 Hz as I did the sweep, between the prim and the sec. winding. Loaded with some reasonable load. Is it because I did the stupid thing of going across the bobins? But 1:2 was good.
Of course
I have to say I know nothing.
These things are so complicated.
Alexander, May I tell a little story -
Of course
I have to say I know nothing.
Alexander, May I tell a little story -
I bought a Chinese 10K-10K amorphous transformer double-C with two discrete winding stacks; it came with centre taps. But it rung extraordinarily. Still, I tested as a choke (all windings in series), no ringing, bandwidth to 150kHz! 210 Henries measured. 45 mA capability. So that way, unintended, a great anode load (10Y..). So what was wrong? couldn't find out. Put aside.
Some time ago I thought, can I use it as 10K-2K5 1/2 transformer? or in fact 2K5 to 15K (1/3) to use it as driver? So I opened the transformer winding to get to the solder patch. I took the two parts apart, and tested.
Behold, with one section it was beautiful, as soon as I attached the second secondary (in series with that of the other winding) it went crazy, big disparity in the bandwidth, big phase difference even at 500 Hz as I did the sweep, between the prim and the sec. winding. Loaded with some reasonable load.
Some time ago I thought, can I use it as 10K-2K5 1/2 transformer? or in fact 2K5 to 15K (1/3) to use it as driver? So I opened the transformer winding to get to the solder patch. I took the two parts apart, and tested.
Behold, with one section it was beautiful, as soon as I attached the second secondary (in series with that of the other winding) it went crazy, big disparity in the bandwidth, big phase difference even at 500 Hz as I did the sweep, between the prim and the sec. winding. Loaded with some reasonable load.
Of course
I have to say I know nothing.
These are a bit dark tunnel situations. Without being aware of the interleaving pattern, I cannot give you conclusive reasons. Here a few examples could be helpful for you:
-Separate windings connected the wrong way could give heavy ringing close to audio or within audio range. For example two big primary sections physically far away, but quite capacitively coupled will ring badly due to high primary to primary leakage interconnected with high capacitance. This usually brings a dipping resonance. Such capacitance can even occur from core to bobbin or section to section.
-Series connection of secondaries will distribute the capacitance differently. Beginner audio transformer designers tend to prefer all parallel secondaries due to the equal voltage gradient and turn ratio for all layers. Yes, switching secondaries from parallel to series can wreck a specific transformer's HF performance.
-Sequence of winding connections is paramount as well. One must especially study the capacitance distribution and its effects on HF response.
Short conclusion. By simply connecting windings of an audio transformer without further knowledge of its construction, you're wildly guessing.
-Separate windings connected the wrong way could give heavy ringing close to audio or within audio range. For example two big primary sections physically far away, but quite capacitively coupled will ring badly due to high primary to primary leakage interconnected with high capacitance. This usually brings a dipping resonance. Such capacitance can even occur from core to bobbin or section to section.
-Series connection of secondaries will distribute the capacitance differently. Beginner audio transformer designers tend to prefer all parallel secondaries due to the equal voltage gradient and turn ratio for all layers. Yes, switching secondaries from parallel to series can wreck a specific transformer's HF performance.
-Sequence of winding connections is paramount as well. One must especially study the capacitance distribution and its effects on HF response.
Short conclusion. By simply connecting windings of an audio transformer without further knowledge of its construction, you're wildly guessing.
Thanks, very instructive. Yes it could only have been capacitative via the core (as the two halves are on separate legs).
My take away. Only trust a good designer!
My take away. Only trust a good designer!
With double bobbins single C-core geometry, even bobbin to bobbin capacitance can significantly play, together with sleeper leakage between the two legs. If it is a multitap choke, even separate choke windings can act as pseudo secondaries and can ring badly if their neighboring surroundings interlink them with a high capacitance factor. It's a classical example why one should treat each department as a separate transformer. And every situation has specific requirements. For example you might get good performance with a specific windings connection for a Push-pull transformer, but not for SE and vice-versa.