My output voltage is quite low on hand wound toroid transformer. I did match the frequency to source AC, used proper core, and both wound in same direction. What is efficiency "percentage difference" of primary not wound exactly over secondary, just wound separate on core? It just looks visually better with 2 different colors insulation.,at separate placements on core.
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Even with a toroid, you cannot escape the basic laws of physic: the leakage inductance, which is likely to cause your problem doesn't depend on the core, just on the geometric configuration.
It would remain ~the same if you used a wooden core. Of course, such a core would lead to impossibly high magnetizing currents, which is why a high permeabilty core is desirable.
If you want to minimize the leakage, you need to place the two windings as close as possible: bifilar, P/S sandwiching, etc. but this this may not be compatible with safety requirements
It would remain ~the same if you used a wooden core. Of course, such a core would lead to impossibly high magnetizing currents, which is why a high permeabilty core is desirable.
If you want to minimize the leakage, you need to place the two windings as close as possible: bifilar, P/S sandwiching, etc. but this this may not be compatible with safety requirements
Equally .. don't forget that the leakage inductance is a useful thing if what you want is a measure of inherent filtering against pass-through of all the HF noise, on the incoming Mains supply.
People pay a premium for R-core transformers, which essentially what @russwr asks about. the core is toroidal, but the windings physically-separated; the power transfer efficiency-loss remains near-zero, but the slight added leakage inductance, and greatly-reduced coupling capacitance between PRI:SEC windings put them in a sweet-spot for both electrical efficiency - yet natural added filtration of HF noise on the AC main supply, comparable with a split-bobbin E-I style transformer.
Pick your compromises : )
People pay a premium for R-core transformers, which essentially what @russwr asks about. the core is toroidal, but the windings physically-separated; the power transfer efficiency-loss remains near-zero, but the slight added leakage inductance, and greatly-reduced coupling capacitance between PRI:SEC windings put them in a sweet-spot for both electrical efficiency - yet natural added filtration of HF noise on the AC main supply, comparable with a split-bobbin E-I style transformer.
Pick your compromises : )
No percentage efficiency difference, core is the "unifying/joining" element between windings, as long as both are wound around same core (which they are), it´s the same.
Capacitance and parasitic inductance are minor side effects compared to the main job: transferring power/energy from one winding to the other.
Main mechanism, by far, is that one winding induces a varying magnetic field in the core, which is then uniform and available "everywhere" around that core, whether it´s EI, Toroid, or any fancy shape.
Then said variable flux around that varying magnetic circuit induces a varying Voltage in any other coil wound around that core.
When in doubt, it´s always good and safe to go back to "basic principles".
Besides that main mechanism, there is some slight (by comparison) direct coil to coil coupling, but its contribution is minimal.
There is also some capacitive coupling, same comment.
Existing and measurable phenomena, but small an not significantly affecting efficiency.
Russ probably means "regulation" when he writes "efficiency". Leakage does not affect efficiency, but the end result at the load looks similar.
Leakage can be compensated by a series cap in the secondary circuit. For low voltages, it is not practical due to the large value (unpolarized) required, and it is only compatible with bridge rectifiers.
Leakage can be compensated by a series cap in the secondary circuit. For low voltages, it is not practical due to the large value (unpolarized) required, and it is only compatible with bridge rectifiers.
