I What Specifications Are Needed for a Plasma Device Power Supply?

[naviakam]

TL;DR Summary

What are the specifications for a power supply to be used in a plasma device?

In a plasma device, the plasma is generated by applying high voltage in a gas. What are the specifications for the power supply producing such plasma?
The output must be AC or DC? Pulsed or not? What are the current, voltage, etc...?

 

[artis]

@naviakam Well I think you should first state what device you have in mind as there are different devices that produce plasmas of various kinds.
From your short description I take that you are thinking about the most simple of them all , called the "Fusor"
Or more broadly the Hirsch-Farnsworth Fusor
https://en.wikipedia.org/wiki/Fusor

 

[naviakam]

@naviakam Well I think you should first state what device you have in mind as there are different devices that produce plasmas of various kinds.
From your short description I take that you are thinking about the most simple of them all , called the "Fusor"
Or more broadly the Hirsch-Farnsworth Fusor
https://en.wikipedia.org/wiki/Fusor

The question is from power supply (PS) point of view, for example, if the PS is AC, pulsed and with specified V and I, can it produce plasma or what if it is DC? What would be the difference for the plasma if either AC or DC is used?
What will be affected if AC or DC is used? Being pulsed or non-pulsed, affects what? how about the influence of the I and V?

 

[artis]

A pulsed supply is an AC supply, the voltage can be pulsed without changing polarity or changing polarity.
DC supply gives non-pulsed steady value of Voltage , at least in theory.

A AC supply can produce plasma , any voltage DC or AC across a gas that is sufficiently high to produce an electric discharge through the gas can produce a plasma, but the conditions will vary , in AC the plasma might get produced and then cool off back to a gas during the part where the voltage/current decreases.
Gas discharge lamps work this way, which is why they flicker at the frequency of AC.

Normally you would want a DC supply to not let the plasma cool during moments of no voltage/current.

What exactly is it that you are trying to understand?

 

[naviakam]

A pulsed supply is an AC supply, the voltage can be pulsed without changing polarity or changing polarity.
DC supply gives non-pulsed steady value of Voltage , at least in theory.

A AC supply can produce plasma , any voltage DC or AC across a gas that is sufficiently high to produce an electric discharge through the gas can produce a plasma, but the conditions will vary , in AC the plasma might get produced and then cool off back to a gas during the part where the voltage/current decreases.
Gas discharge lamps work this way, which is why they flicker at the frequency of AC.

Normally you would want a DC supply to not let the plasma cool during moments of no voltage/current.

What exactly is it that you are trying to understand?

1. (non-pulsed): Thus both AC and DC can produce plasma as long as the supply is on? what would be difference between AC made plasma and DC made?

2. How it could be made pulsed? Only AC can be pulsed or DC too?

We may take DBD plasma, is it AC or DC? Pulsed or non? what would be affected in plasma if it uses other way around?

 

[artis]

@naviakam I think you first need to learn about different types of AC waveforms and DC and power supplies in general and only then try to understand them in terms of plasma physics and how they are used in various devices.

Let me just say that plasma is plasma , plasma has certain characteristics such as polarized or neutral (more ions or electrons or both in balance) , plasma has temperature which is the value of the average kinetic energy of a plasma particle (ion or electron), plasma has pressure with which it presses against a wall or a magnetic field and this is proportional to plasma density (how many particles are within a given volume) , plasma has some other more complicated characteristics but these few ones are enough to describe any plasma. You can try to think of how various electric waveforms if passed through a plasma would influence it.
Yes plasma is conductive which is why you can pass electricity through it and influence it by electricity in the first place. Electricity is just the passage of charge under a potential difference, plasma is just a volume of free charges + neutral particles if there are any like neutrons.

 

[DaveE]

I think you're looking at this backwards. First figure out why you want a plasma, the physics will then create requirements for the power supply. But, yes, AC, DC, RF, pulsed, constant, these are all valid possibilities. I don't know which one you want either. But in my experience (I've worked with all of these combinations in gas lasers*), the power supply designer NEVER gets to choose which type.

* edit: Oops, wrong. I've never made an AC power supply for plasmas, although I've played a bit with neon sign transformers. These would normally be for low cost applications, like the fluorescent room lighting.

 

[naviakam]

@naviakam I think you first need to learn about different types of AC waveforms and DC and power supplies in general and only then try to understand them in terms of plasma physics and how they are used in various devices.

Let me just say that plasma is plasma , plasma has certain characteristics such as polarized or neutral (more ions or electrons or both in balance) , plasma has temperature which is the value of the average kinetic energy of a plasma particle (ion or electron), plasma has pressure with which it presses against a wall or a magnetic field and this is proportional to plasma density (how many particles are within a given volume) , plasma has some other more complicated characteristics but these few ones are enough to describe any plasma. You can try to think of how various electric waveforms if passed through a plasma would influence it.
Yes plasma is conductive which is why you can pass electricity through it and influence it by electricity in the first place. Electricity is just the passage of charge under a potential difference, plasma is just a volume of free charges + neutral particles if there are any like neutrons.

Just I want to understand physically that what are the criteria to choose either AC or DC power supply (eg for DBD). And what are the benefit of pulsed AC or DC. How we make them to be pulsed.

 

[naviakam]

I think you're looking at this backwards. First figure out why you want a plasma, the physics will then create requirements for the power supply. But, yes, AC, DC, RF, pulsed, constant, these are all valid possibilities. I don't know which one you want either. But in my experience (I've worked with all of these combinations in gas lasers*), the power supply designer NEVER gets to choose which type.

* edit: Oops, wrong. I've never made an AC power supply for plasmas, although I've played a bit with neon sign transformers. These would normally be for low cost applications, like the fluorescent room lighting.

Just I want to understand physically that what are the criteria to choose either AC or DC power supply (eg for DBD). And what are the benefit of pulsed AC or DC. How we make them to be pulsed.

 

[naviakam]

I saw in a few papers that for DBD, AC power supply is used. What are AC benefits over DC here?
And what would be the result if it is pulsed (AC or DC) over non-pulsed?

 

[artis]

@naviakam Well you should have been more clear from the beginning, if you are talking specifically about DBD which I suppose is meant "dielectric barrier discharge".

Well have you read enough about the method? Do you understand how it works? I think if you would these questions you ask would answer themselves.
https://en.wikipedia.org/wiki/Dielectric_barrier_discharge

So explain why do you think for typical DBD a DC power supply doesn't work but instead AC of high frequency is used ?

 

[naviakam]

@naviakam Well you should have been more clear from the beginning, if you are talking specifically about DBD which I suppose is meant "dielectric barrier discharge".

Well have you read enough about the method? Do you understand how it works? I think if you would these questions you ask would answer themselves.
https://en.wikipedia.org/wiki/Dielectric_barrier_discharge

So explain why do you think for typical DBD a DC power supply doesn't work but instead AC of high frequency is used ?

In the reference provided, AC is used (DC also used) and pulsed has higher efficiency. The question is why mostly AC is used and why pulsed has higher efficiency?
Next question is how to make it pulsed?
In simple physics words please.

 

[artis]

In the reference provided, AC is used (DC also used) and pulsed has higher efficiency. The question is why mostly AC is used and why pulsed has higher efficiency?
Next question is how to make it pulsed?

These questions require multiple lessons in electronics I'm afraid it cannot be done , you have to start reading yourself the fundamentals and then build from there.
These are rather simple matters if you have problems understanding them then I suggest start from one level below with simpler stuff.

I asked you to explain yourself how you think the DBD in AC works , you did not do that , instead just repeated the questions.
Did you read the wikipedia article at least fully?
Do you understand how a DBD device is made and how it works , and if the plates have an insulating layer why DC in that case doesn't work?

 

[naviakam]

These questions require multiple lessons in electronics I'm afraid it cannot be done , you have to start reading yourself the fundamentals and then build from there.
These are rather simple matters if you have problems understanding them then I suggest start from one level below with simpler stuff.

I asked you to explain yourself how you think the DBD in AC works , you did not do that , instead just repeated the questions.
Did you read the wikipedia article at least fully?
Do you understand how a DBD device is made and how it works , and if the plates have an insulating layer why DC in that case doesn't work?

With DC, gas breaks down, but charges are accumulated on insulator and opposite electric field is generated, then no plasma! But AC, polarity changes and this problem resolved.

 

[naviakam]

With DC, gas breaks down, but charges are accumulated on insulator and opposite electric field is generated, then no plasma! But AC, polarity changes and this problem resolved.

If correct, then how pulsed increases the efficiency?

 

[artis]

With DC, gas breaks down, but charges are accumulated on insulator and opposite electric field is generated, then no plasma! But AC, polarity changes and this problem resolved.

Why would there be an opposite electric field? Think of a capacitor because this is essentially a capacitor with an increased air gap and two insulating layers instead of one.
There are opposite charges but E field direction is the same. You can do a simple test for this take a piece of paper and drawn 4 vertical lines. two outer ones are electrodes as in a capacitor, two inner ones are insulators.
Place + and - on the outer plates , you will see that for the + plate the insulator that faces it get's a - charge, then the other side of that insulator becomes +, then the next insulator facing that is again - and the other side again + and then finally the outer electrode becomes -

The gas breaks down after enough charge has accumulated and a E field is established not before.
With DC the only way to make continuous plasma is by arc discharge through such plasma , with AC one can use induction as used in tokamaks or varying charge and E field as in the DBD case.

Do you understand what pulsed means? Pulsed as opposed to what , sine wave ?
One needs to compare specific examples not just generic words as they mean nothing.
There can be various pulses , square wave, sawtooth, sine wave etc.
Just mentioning pulsed doesn't say a lot and so no meaningful answer can be given.

But as I said you need to use google and read about pulse waveforms , current etc to further understand a device like DBD. Unlike other plasma devices , DBD has much more to do with electrical engineering than plasma physics, apart from the fact that an electrical arc through a gas creates a plasma.

 

[naviakam]

Why would there be an opposite electric field? Think of a capacitor because this is essentially a capacitor with an increased air gap and two insulating layers instead of one.
There are opposite charges but E field direction is the same. You can do a simple test for this take a piece of paper and drawn 4 vertical lines. two outer ones are electrodes as in a capacitor, two inner ones are insulators.
Place + and - on the outer plates , you will see that for the + plate the insulator that faces it get's a - charge, then the other side of that insulator becomes +, then the next insulator facing that is again - and the other side again + and then finally the outer electrode becomes -

The gas breaks down after enough charge has accumulated and a E field is established not before.
With DC the only way to make continuous plasma is by arc discharge through such plasma , with AC one can use induction as used in tokamaks or varying charge and E field as in the DBD case.

Do you understand what pulsed means? Pulsed as opposed to what , sine wave ?
One needs to compare specific examples not just generic words as they mean nothing.
There can be various pulses , square wave, sawtooth, sine wave etc.
Just mentioning pulsed doesn't say a lot and so no meaningful answer can be given.

But as I said you need to use google and read about pulse waveforms , current etc to further understand a device like DBD. Unlike other plasma devices , DBD has much more to do with electrical engineering than plasma physics, apart from the fact that an electrical arc through a gas creates a plasma.

Pulsed as opposed to continues. Apply voltage with specified repetition rate.

 

[Tom.G]

The OP messaged me as below (no idea why I was chosen!)

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?

@naviakam , I am putting your message here, where it belongs, in your main thread so others can learn from it and also so others can help answer it.

High voltage supplies usually have a very low current rating.
The 6kV reading is most likely because the oscilloscope is loading (drawing to much current from) the power supply.

You can use Ohms Law (Google it if needed) to find out how much the oscilloscope is loading the supply. You will need the current rating of the supply and the impedance (resistance) of the oscilloscope probe you are using.

Solution is to use a higher impedance probe or a higher current 30kV supply. Or move the plates of the plasma generator closer together.

Cheers,
Tom

 

[DaveE]

Me too. I ignored it. I have no comment for anyone working with 30KV spark gaps. Especially if their question doesn't sound well formed. How am I supposed to know why they're measurement was off, anyway?

PS: No. I won't help you make rockets, bombs, poisons, giant batteries, computer viruses, real viruses, things with whirling blades, or HV circuits. Especially if I have no idea who you are.

 

[naviakam]

The OP messaged me as below (no idea why I was chosen!)

@naviakam , I am putting your message here, where it belongs, in your main thread so others can learn from it and also so others can help answer it.

High voltage supplies usually have a very low current rating.
The 6kV reading is most likely because the oscilloscope is loading (drawing to much current from) the power supply.

You can use Ohms Law (Google it if needed) to find out how much the oscilloscope is loading the supply. You will need the current rating of the supply and the impedance (resistance) of the oscilloscope probe you are using.

Solution is to use a higher impedance probe or a higher current 30kV supply. Or move the plates of the plasma generator closer together.

Cheers,
Tom

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.

 

[Tom.G]

Then disconnect the oscilloscope and see if you get a discharge.

 

[naviakam]

Then disconnect the oscilloscope and see if you get a discharge.

If worked, then the probe has problem and must be changed? If still didn't discharge, power supply has problem?

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!

 

[naviakam]

This is so offensive. I want this thread to be completely removed please.

 

[anorlunda]

This is so offensive. I want this thread to be completely removed please.

Click on report and pass your request to mentors.

 

[berkeman]

This is so offensive. I want this thread to be completely removed please.

Not removed, locked. It is apparent that you do not have the background to do this project, let alone safely. Please find a local expert who can work with you and Mentor you in person. Thread is done.