Thor primary circuit measurements

The primary circuit is composed by 9.5 turns of copper pipe (primary coil) and a 0.1 μF pulse capacitor. Coil and capacitor were connected in parallel and driven by a HP33120 waveform generator. The injected current was monitored for maximums in order to find the values of the circuit resonance frequencies. The results are reported in Table 1, for different coil tap positions.

Subsequently, in order to calculate the coupling coefficient, the inductance of the primary coil tapped at 9.5 turns was measured using a Fluke PM6306 RLC meter (at 1 kHz and 1 VAC): after subtracting the cables inductance, the value obtained was 99.1 μH. Primary and secondary coils were then connected in series and the resulting inductance L_t was measured using the same instrumentation; the elevation of the primary coil in respect of the secondary coil was varied as much as allowed by the mechanics. The mutual inductance M and the coupling coefficient k were calculated according to the following equations, assuming L₂ = 80.22 mH

In Table 2 below, the primary coil elevation is defined as the distance from the underlying PVC table, but also the distance from the secondary coil base turn is given, for reference.

Figure 2: Primary and secondary coils coupling coefficient vs. primary elevation.

The value of the primary capacitor was measured using a Fluke PM6306 RLC meter (at 65 kHz and 1 VAC); the reading was 0.09678 μF, with an equivalent parallel resistance of 5.97 kohms. Based on this capacitance value and the measurements in Table 1, the primary inductance vs. the tap position could be calculated with the following relation