Hello.
Please see the attached images which shows our capacitively gas discharge circuit. HV box has single output of 30 kV.
Before thyratron (fast electrical switch) is on, everything looks clear and no need to worry. But after thyratron is on, among 30 kV or 0, which voltage is right on the HV box side? Although this circuit have works so far. I've always confused this.
I guess the best scenario is the HV side becomes 0 zero and I've believed this way but...why and how?
If this circuit is bad, how can HV side be automatically cut when thyratron is on so the box is protected from , for example, huge current drawing from the box to ground by electrical short?
It would be 0V. Observe the ground is connected to the HV Output. As for the HV side protection I cannot think of a simple diode based network. I think you would have to use a second switch for control between HV out and capacitor 0V node. It can however be connected to the thyratron where the gate supply for the second switch is when thyratron-on and the gate opens the junction isolating the HV side. [Sort of like the flyback diode in DC-DC converters]
Thanks for reply.
I've got the idea of inserting strong resistor between capacitor and HV side. With this resistor, current drawn from HV box will be limited to 30 kV/R, where R is resistance of the resistor.
A current-limiting resistor is always recommended in between a HV DC supply and a HV capacitor (and especially in your circuit topology where the DC supply can be shorted by the thyratron), because the initial current when the capacitor is not charged can become very large. So far, the current-limiting circuits of your Glassmann have protected you.
Keep in mind the losses in your charging resistor though! It can become quite hot when not properly dimensioned and you are running your switch at a high repetition rate.
When the thyratron is ON, the voltage on its anode is close to 0. The HV of 30 kV is applied mainly to the charging resistor (or inductance) - inside the HV unit. All is in accordance with Ohm's law. Generally, a limiting resistor (limits the current of HV device) is always present in such systems.
Most probably the high voltage Glassman power supply box is a constant current generator, and the magnitude of this current is such that it is less than the holding current of the Thyratron, so that the Thyratron can shut off,after being switched on.Here the shorting to ground has no problem as even with short, only this current can flow to ground.In case of a voltage source as power supply there must be a resistance between the HV outlet of the power supply and the junction of switch and capacitor.The value of this resistance must be such as to keep the charging current below the holding current.
I hope this will clarify your doubt and will help you out in your work.