On Fri, Mar 26, 2021 at 07:08 AM, alan victor wrote:
Many simulators apply default series R to L and perhaps C to prevent creating
a singularity matrix. In some cases you can over ride the default.
I use the now free Micro-Cap 12:
This is my Micro-Cap file ¡°Parallel LC resonans - Current Cancel 888453 Hz, LC res 918881 Hz - remade from scratch.cir¡±:
Micro-Cap does apply a default high impedance R to connect parts of the circuit to prevent creating a singularity matrix, and it tells me when it does. I did not get a warning when I just remade this circuit to see if I would get a warning.
Reactance at LC Resonance frequency 918881 Hz is 86.603 Ohms. At 888453 Hz XC = 89.569 Ohms, XL = 83.735 Ohms. The Q-factor is 4174.
The small RS 10 mOhms in the coil and capacitor doesn¡¯t seem to do much to do much to the current curves, except create beats on top of the 888630 Hz waves when I put RS in the coil and capacitor to 0 Ohms. Possibly being modulated by the 918881 LC-resonance frequency ??
[ ?IMAGE 0 ]
Seemingly no parallel Ohm from the Current Source, as I get the exact same result with a 1000 Mega Ohms resistor in series.
Input at frequency where Current Cancel, at 888453 Hz:
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?[ ?IMAGE 1, 2 and 3 ]
Input at LC-Resonance frequency 918881 Hz:
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[ ?IMAGE 3, 5 and 6 ]?
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Note that on the LC resonance frequency the two Currents have mismatching amplitudes = NOT cancelling.
In real life I don¡¯t recall any sign of a resonance / rise in voltage amplitude on a frequency right below the LC resonance frequency, but I do see some kind of resonance on the nanoVNA with the phase angle being 0 and hte reflex coefficient (imaginary) being 0 at that frequency.
It started out with me pondering why I have a problem achieving cancellation at the Self Resonant Frequency of coils, where it is very easy to locate the LC-resonance point as the Current is 0 degrees phase shifted related to the Voltage. But it is a problem getting the current flat.
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Simen Tobiassen
