Hi there,
I'm trying to figure out the current waveform of my surge generator discharging through some pieces of wire. It's a 235uF 1200V capacitor bank with a 1000A dics thyristor as the main switch. I can monitor the bank voltage through a high voltage divider (ratio 100:1) but not the discharge current. I tried to hook up the probe to a 2mm dia, 13cm copper wire in series with the capacitors and obtained the following waveform. Ch1 was the probe hooked to the wire, while Ch2 was the one connected to the voltage divider, which was connected directly to the capacitors.
Using Ohms law's U=i*r we quickly ended up with a result of 24453 Amps peak current, but there was 4 strands of wire in total (I only hooked the probe up to one) so we ends up with 97815 Amps through my capacitor. At this current the thyristor would had gone already, but it still functioning fine so there must be an hidden factor that make the calculation pointless.
I tried to calculate the inductance of the copper wire and ended up with a value 125nH, given that the initial oscillation lasted for 12.5us or so and the current rise rate must be less than 200A/us or the thyristor will be killed, then we can see that this inductance could induce on the wire a maximum voltage of 25V! This means that the inductance is considerable in this situation, so the Ohms Law's now become U=L*d^2(i)/dt^2 + R*i. How could we accurately measure the current in this situation, when we had no special equipment other than a oscilloscope?
I'm trying to figure out the current waveform of my surge generator discharging through some pieces of wire. It's a 235uF 1200V capacitor bank with a 1000A dics thyristor as the main switch. I can monitor the bank voltage through a high voltage divider (ratio 100:1) but not the discharge current. I tried to hook up the probe to a 2mm dia, 13cm copper wire in series with the capacitors and obtained the following waveform. Ch1 was the probe hooked to the wire, while Ch2 was the one connected to the voltage divider, which was connected directly to the capacitors.
Using Ohms law's U=i*r we quickly ended up with a result of 24453 Amps peak current, but there was 4 strands of wire in total (I only hooked the probe up to one) so we ends up with 97815 Amps through my capacitor. At this current the thyristor would had gone already, but it still functioning fine so there must be an hidden factor that make the calculation pointless.
I tried to calculate the inductance of the copper wire and ended up with a value 125nH, given that the initial oscillation lasted for 12.5us or so and the current rise rate must be less than 200A/us or the thyristor will be killed, then we can see that this inductance could induce on the wire a maximum voltage of 25V! This means that the inductance is considerable in this situation, so the Ohms Law's now become U=L*d^2(i)/dt^2 + R*i. How could we accurately measure the current in this situation, when we had no special equipment other than a oscilloscope?
