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Author Topic: Effects of perm. magnets on bifilar toroid transformer output  (Read 15886 times)

Offline baroutologos

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Re: Effects of perm. magnets on bifilar toroid transformer output
« Reply #15 on: June 03, 2010, 12:27:58 AM »
This is confusing to me.  Placing the magnet near the toroid, as has been measured, lowers the inductance.  Doesn't this also mean that the saturation point is reduced as well, meaning that it reaches saturation sooner?  Would reaching saturation sooner cause doubled output voltage while reducing input current?  Because that is how it appears.

Wouldn't reduced inductance, decrease the opposition to current flow, resulting in higher input current?  Because that is not what I am seeing, I see reduced input current.

In Kapanadze thread, i posted a number of photos showing diminishing inductance of a coil wound over a solenoid with iron core (few laminations), toroid and stacked toroids by applying them a external flux (bias b-flux). In pulsing the setups aforementioned a spectacular increased current consumption is shown.
BUT, i have two large toroids (red, 50mm diam. sorry do not know grade or type) that exhibit the opposite extactly behaviour. Biasing them with neo magnets or electromagnets no matter how strong, their inductunce is spectacular increased and current minimized.

In the link of experimental photos i have proviced i have a folder that is called big toroid anomaly.
I verify your claims void.
Different matterials will behave differently.

Offline exnihiloest

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Re: Effects of perm. magnets on bifilar toroid transformer output
« Reply #16 on: June 03, 2010, 08:56:58 AM »
Hi exnihiloest,

What you propose could be possible but in this particular case we should see some sinusoid voltage waveform at the output instead of the still uggly pulse shape.  LC resonance always involves forming sinusoid or distorted sinusoid waves but not such straight lined pulse shapes.

You are generally right, especially at low frequencies (< 1 Mhz). Nevertheless there are often different modes of resonance at very different and not harmonic frequencies (for example due to capacities between near turns but also between successive layers, or due to L if the wounding is built in several separated blocks...). This is particularly true at HF frequencies, because we are no more in the quasi-stationary regime, there is propagation effect along the wire (the current cannot be considered constant in the whole circuit).
To be sure that the observed signal is not due to such a phenomenon, the only way is to use a sin generator and to scan frequencies up to 20 Mhz. If there is not only one resonant frequency, the observed "ugly" signal is probably due to HF components of the pulse that make "ringing" the coil.