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Audio and Video Talk
Valves / Vacuum Tubes
EI VS C-Core for PP transformer question
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<blockquote data-quote="Ampdog" data-source="post: 599672" data-attributes="member: 144"><p>It definitely has to do with measuring at zero bias. It also depends on at what ac voltage level and frequency you measure. </p><p></p><p><span style="font-size: 11px">The classic approach is to measure at 5Vac, 50 Hz, which represents a low exitation; i.e. enough inductance for soft music. Inductance increases as the exitation rises up the slope of the core BH curve, to flatten off again as saturation point is reached. But with dc 'in' the core one is already somewhere up the slope.</span></p><p><span style="font-size: 11px"></span></p><p></p><p>It requires a high impedance current source to place dc through the transformer when measuring inductance in SE transformers - quite a set-up. I have not done such measurements on SE-transformers, and Hammond does not state how their measurements are done, viz at what dc on the primary, frequency etc. You found quite a difference; I would expect less. But not knowing the conditons one cannot come to further conclusions.</p><p></p><p><strong>@ Karel:</strong></p><p></p><p>I did not closely inspect your excellent instrument face photos. At what exitation does Yves specify inductance etc.? </p></blockquote><p></p>
[QUOTE="Ampdog, post: 599672, member: 144"] It definitely has to do with measuring at zero bias. It also depends on at what ac voltage level and frequency you measure. [SIZE=11px]The classic approach is to measure at 5Vac, 50 Hz, which represents a low exitation; i.e. enough inductance for soft music. Inductance increases as the exitation rises up the slope of the core BH curve, to flatten off again as saturation point is reached. But with dc 'in' the core one is already somewhere up the slope. [/SIZE] It requires a high impedance current source to place dc through the transformer when measuring inductance in SE transformers - quite a set-up. I have not done such measurements on SE-transformers, and Hammond does not state how their measurements are done, viz at what dc on the primary, frequency etc. You found quite a difference; I would expect less. But not knowing the conditons one cannot come to further conclusions. [b]@ Karel:[/b] I did not closely inspect your excellent instrument face photos. At what exitation does Yves specify inductance etc.? [/QUOTE]
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Valves / Vacuum Tubes
EI VS C-Core for PP transformer question
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