Re: Meissner oscillator - inductance problem

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Original poster: "Qndre Qndre" <qndre_encrypt@xxxxxxxxxxx>

Hello Ed,

thanks for your reply.

The oscillator circuit is from a flourescent lamp inverter which is 
similar to this one ( 
http://www.elektronik-kompendium.de/forum/upload/20050607095524.gif ) 
but has different capacitances/inductances.

The differences from the circuit displayed are: There is no capacitor 
C1. The winding W1 is known to have an inductance of 22.5 uH from the 
center tap to one end or 2 * 22.5 uH = 45 uH total inductance and a 
resistance of 0.15 Ohms from the center tap to one end or 2 * 0.15 = 
0.3 Ohms total resistance. The capacitor C2 in the primary LC circuit 
is known to have a capacitance of 47 nF. The feedback winding W2 is 
known to have an inductance of 1.3 uH and a resistance of 45 
milliOhms. The winding W3 being the coil in the secondary circuit is 
known to have an inductance of 242 mH as well as a resistance of 310 
Ohms. The coupling coefficient of the windings W1, W2 and W3 is known 
to be 0.78 . The capacitance in the secondary circuit is known to be 
25 pF. All the other values are the same as in the schematic.

The whole circuit's resonant frequency with the choke "Dr" calculates 
to 62.2 kiloHertz using a PSpice model which is somewhat low. Without 
the choke it's at about 104 kiloHertz which comes closer to the 
calculated resonant frequency using Thomson's equation which is about 
155 kiloHertz for the primary LC circuit and about 64.7 kiloHertz for 
the secondary LC circuit. I don't know why the two resonant 
frequencies don't match but this can be corrected relatively easy by 
replacing the secondary circuit's capacitor with one with a lower value.

After these changes, stop making the choke for current limiting 
interfer with the primary circuit somehow, possibly by replacing it 
with a resistor, and making the secondary capacitance smaller, the 
circuit may be a quite useful high frequency low power source.

Regards, Q.