 |
 |
Figure 1: Typical secondary voltage waveform, with four beats. |
Figure 2: Zoomed first two beats from Figure 1. |
 |
 |
Figure 3: Another secondary voltage waveform sample. |
Figure 4: A third secondary waveform sample, with three beats only. |
The secondary voltage waveform is regarded as the most significant indicator to provide an insight into Thor's functionality. Any variation in the primary or secondary circuits components, or of the coupling coefficient, affects noticeably the shape of the voltage generated. Given that, in this context, the voltage absolute magnitude is unimportant, the voltage on the secondary top electrode can be measured by an oscilloscope with its input probe left unconnected. This method is preferred for its intrinsic simplicity and its non-intrusive characteristic. In all of the following measurements the coupling coefficient was set to 0.187 and the rotating spark gap speed was regulated to provide a constant break rate of 300 Hz; the primary coil was tapped at 7.5 turns.
The primary capacitor charging voltage was set about 11-12 kV, as suited to obtain a regular triggering of the rotating spark gap, yet without developing any leaders from the top electrode and, therefore, avoiding to load it. The waveform recorded had a very good repeatability and included a variable number of beats (3 - 4) according to the exact time instant the spark gap stopped conducting (Figure 1 to Figure 4).
|
|
Figure 1: Typical secondary voltage waveform, with four beats. |
Figure 2: Zoomed first two beats from Figure 1. |
|
|
Figure 3: Another secondary voltage waveform sample. |
Figure 4: A third secondary waveform sample, with three beats only. |
The primary capacitor charging voltage was set about 14 kV, resulting in continuous emission of leaders from the top electrode and a noticeable loading of the secondary circuit (Figure 5). The energy originated from the primary capacitor was almost completely dissipated within the first two beats, followed by the spark gap opening and free oscillation in the secondary circuit.
The primary capacitor charging voltage was set about 14 kV and a grounded rod was placed at 50 cm from the top electrode. Thor's operation produced a continuous discharge upon the rod and a typical secondary voltage waveform as reported in Figure 6. The discharge developed within the first beat, resulting in a relatively low impedance loading of the secondary circuit and a complete damping of the oscillations.
 |
 |
| Figure 5: Secondary voltage waveform when leaders are produced. | Figure 6: Secondary voltage waveform with a ground discharge. |
The secondary base current (Figure 8) was measured with a Pearson probe mod. 110A (0.1V/A) driving a 50 ohm load. The reading, correctly halved, results in 50 mV/A. Voltage magnitude (Figure 7) was measured simultaneously with a flying probe. Note that the current reads as high as 16 Apeak.
 |
| Figure 7: Secondary voltage (unloaded). |
 |
| Figure 8: Secondary current (50 mv/A). |