Troubleshooting 30kV Power Supply: Possible Problems and Solutions

[naviakam]

TL;DR Summary

having problem to get discharge in air

I am using a power supply (30 kV, 20 kHz) to discharge in air between two electrodes separated by an insulator. For 30 kV applied voltage, oscilloscope shows only 6 kV, and no discharge occurs. What are possible problems and solutions?

 

[Baluncore]

The input impedance of an oscilloscope is usually only 1 Megohm, or 10 Megohm on the 10x probe range. Maybe the 30 kV supply is overloaded by the probe.

There are special high voltage probes available for oscilloscopes. How are you using an oscilloscope to view what might be 30 kV ?

 

[naviakam]

The input impedance of an oscilloscope is usually only 1Meg, or 10 Meg on the 10x probe range. Maybe the 30 kV supply is overloaded by the probe.

There are special high voltage probes available for oscilloscopes. How are you using an oscilloscope to view what might be 30 kV ?

Using a high voltage probe.

 

[Baluncore]

Using a high voltage probe.

Does a discharge occur when you do not use the oscilloscope or probe?

 

[naviakam]

The input impedance of an oscilloscope is usually only 1 Megohm, or 10 Megohm on the 10x probe range. Maybe the 30 kV supply is overloaded by the probe.

There are special high voltage probes available for oscilloscopes. How are you using an oscilloscope to view what might be 30 kV ?

The problem is I do not get any discharge, while such voltage must breakdown the gas!
I use a high voltage probe to see the voltage on the oscilloscope. The ampere meter on the power supply does not show anything. The only thing I can see is the manually adjusted (30 kV) voltage on the power supply and the voltage (6 kV) shown on the oscilloscope.

 

[naviakam]

Does a discharge occur when you do not use the oscilloscope or probe?

did not check that really!

 

[naviakam]

Does a discharge occur when you do not use the oscilloscope or probe?

Then what this shows if I disconnect the probe and get discharge? and if I disconnect probe and do not get discharge, what this shows?

 

[Baluncore]

Then what this shows if I disconnect the probe and get discharge? and if I disconnect probe and do not get discharge, what this shows?

It shows if the probe is overloading the EHT supply.
I need a data sheet.
What is the make and model of the EHT power supply?
What is the make and model of the oscilloscope EHT probe?

 

[naviakam]

It shows if the probe is overloading the EHT supply.
I need a data sheet.
What is the make and model of the EHT power supply?
What is the make and model of the oscilloscope EHT probe?

power supply: https://www.amazing1.com/hv-hf-power-supplies.html#HVHF

oscilloscope: Tektronix 4 channel.

then what shall I do to resolve overloading?

 

[Baluncore]

then what shall I do to resolve overloading?

First identify the parts that do work.
Use “divide and conquer” to find the problem.
Reduce the complexity back to the point where all the parts work separately. Then start assembling it, one step at the time.
For example; Eliminate the spark gap and wires, look at the EHT supply output with the probe and oscilloscope only. If that does not work, test them independently. Check the calibration of the oscilloscope with a known test signal.

Take care, 30 kV may generate X-rays when the discharge takes place.

 

[naviakam]

There is a one k ohm resistor between the power supply ground wire and the ground electrode of device. high voltage probe connected to oscilloscope through 50 ohm connector.
the device (plasma jet) made up of: SS 3 mm diameter rod connected to high voltage inserted inside a quartz tube with 4 mm inner and 8 mm outer diameters. Cu tape around quartz at the bottom is the ground. we must have a discharge within the tube between anode tip and the Cu. but it's strange that with such high voltage we can not get any discharge!
If probe overload the power supply, probe has problem? If still didn't discharge, power supply has problem?

 

[Baluncore]

If probe overload the power supply, probe has problem? If still didn't discharge, power supply has problem?

That is as yet indeterminate. It may be the EHT supply that is faulty, the probe, or the discharge tube. Do not overthink the analysis.
1. You can test the CRO with against it's reference, and other sources.
2. You can test the probe with the working CRO on AC voltage. Does the probe have an AC/DC switch?
3. You can then test the EHT supply with all previously tested items.
4. Lastly you can test the discharge tube.
At any point you may need to back-track, or to check cables and connections.

The 1k resistor from ground to "ground electrode of device" is probably there to conduct leakage currents, to prevent voltages floating and breaking down the insulation. I do not have the schematic diagram of your circuit, or know which particular "device" you might be referring to.
You can post a link, or attach a picture to a post.

 

[naviakam]

That is as yet indeterminate. It may be the EHT supply that is faulty, the probe, or the discharge tube. Do not overthink the analysis.
1. You can test the CRO with against it's reference, and other sources.
2. You can test the probe with the working CRO on AC voltage. Does the probe have an AC/DC switch?
3. You can then test the EHT supply with all previously tested items.
4. Lastly you can test the discharge tube.
At any point you may need to back-track, or to check cables and connections.

The 1k resistor from ground to "ground electrode of device" is probably there to conduct leakage currents, to prevent voltages floating and breaking down the insulation. I do not have the schematic diagram of your circuit, or know which particular "device" you might be referring to.
You can post a link, or attach a picture to a post.

 

[Baluncore]

The dimensions of your discharge tube are almost certainly not the problem. There is something more obvious missing. Like, how the generator current is limited.

How is the ground of the generator connected to the discharge tube?
Where in the circuit is the 1k ?

 

[naviakam]

The dimensions of your discharge tube are almost certainly not the problem. There is something more obvious missing. Like, how the generator current is limited.

How is the ground of the generator connected to the discharge tube?
Where in the circuit is the 1k ?

 

[berkeman]

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