Thor secondary circuit measurements

The inductance of the secondary coil (neglecting the non-uniform current distribution) was measured using a Fluke PM6306 RLC meter (at 1 kHz and 1 VAC). After subtracting the cables’ inductance, the value obtained was 80.22 mH. Then the following setup was arranged in order to measure the secondary circuit resonance frequencies:

1. The secondary coil base was connected to ground through a HP33120 waveform generator.
2. The top toroid was left into place and connected.
3. One end of the primary coil was grounded, the other end was left open.
4. A distance of at least 3 meters was ensured between Thor and any nearby object .
5. The oscillation amplitude was read from an oscilloscope with its input probe left unconnected.

The frequencies where the oscilloscope reading was at a maximum are reported below:

• f_a = 65.56 kHz
• f_b = 220.2 kHz
• f_c = 344 kHz

In order to estimate the secondary circuit quality factor Q, also the two frequencies where the oscillation amplitude was halved were measured: their values were f_a’ = 65.3 kHz and f_a’’ = 65.82 kHz. Then

The circuit resistive loss R₂ was calculated as

The correct value of Q was then found by subtracting the HP33120 output impedance value (50 ohms) from R₂ and recalculating the quality factor with the obtained value