Tweaking an industrial ozone generator help (HV)

[Grazzje]

Hi everyone, I'm new here and I have an exciting challenge on my hands.

I have an ozone generator from China, will be used for water disinfection. Its rated at generating 10 grams of ozone per hour. I would like to reduce this by 10 or 20 fold (0.5 - 1 gram/hour).

http://www.banggood.com/220V-10g-Oz...ble-Sheet-for-Chemical-Factory-p-1070789.html

Ozone Output: 10g
Input Voltage: AC 220V
High Voltage: 3.1kv-3.5kv
Power Consumption: 50W
Gas Feeding: Dry Air or Oxygen
Ozone Generating Method: Corona Discharge
Cooling Method: Ambient Air Cooling

This is the internal circuit at a glance:

So there it all is. I can see the mains coming into a bridge, then through a LC circuit creating the high frequency for the primary flyback windings.



My solution:

I was thinking about using a resistor, calculated by ohms law in series with the corona discharge plates to reduce the overall current going into the circuit. With the information; 3.5kv @ 50w provided by the manufacturer.

My question:

Will this work? Can you think of a better method?

The goal:

Reduce both noise & ozone output.


Thanks in advance
Grazj

 

[Grazzje]

Sorry for double post; from previous electronic education I can find:

Primary side: V=220v P = 50W Therefore: I=50/220 = 0.227A or 227mA @ 220v

Secondary HV side: V=3500v P=50w Therefore I=50/3500 = 0.01428A or 14.2mA @3500v

If I factor in a %25 electrical loss I would have around 10 - 12mA current @ 3500v

Aiming for 2mA @ V=3.5kv Therefore R=3500v / 0.002A = 1750000 ohm or 1.75 mega ohm.

So I am intending to buy 1 mega ohm resistors rated at 10W each and use them in series/paralell to bring this electronic device down to %5 power or so.

Any input is much appreciated. Been a while

 

[BobK]

That will not work, the voltage would be reduced drastically and it would not operate.

Easiest way to make it produce 1/10 of the ozone would be to operate it 1 /10 of the time.

Bob

 

[Grazzje]

That will not work, the voltage would be reduced drastically and it would not operate.

Easiest way to make it produce 1/10 of the ozone would be to operate it 1 /10 of the time.

Bob

THanks for reply bob. I thought that at first, until I saw how loud this thing is. Sounds like burger in a pan frying when it works. I can hear it in the whole house.

If the voltage gap is that sensitive, then maybe much less of a resistance will have a much greater effect at reducing overall noise?

I took a few kilo/mega ohm 3W resistors out of an old TV now. I'm going to try different ones to see its impact on sound levels.

Or will I have to sketch out the circuit and modify it / rebuild an entirely new circuit for the flyback? I'm more than capable of doing so but it seems like there could be an easier way.

There must be a way of doing this without rebuilding the entire thing

 

[duke37]

That will not work, the voltage would be reduced drastically and it would not operate.

Easiest way to make it produce 1/10 of the ozone would be to operate it 1 /10 of the time.

Bob

Bob is right. How are you going to make a silent corona discharge?

 

[Grazzje]

Bob is right. How are you going to make a silent corona discharge?

Hard to avoid the high pitched whine. But the crackling arc lightning can only crackle if it has the current to do so, right? More the current, more it crackles. I see a current-sound relationship here

Just for some chit chat, heres what happened with the resistors:
10 mega ohm - the circuit made a sound like a starter clicking
333 kilo ohm - high pitched mosquito sound
57k - higher pitch
25k - i saw corona arc on one location and the resistor was quickly fried (I didn't expect it to last)

So this thing has a lot of power if it can fry a 3w resistor in about 1 second. Need to reduce that

What if I found the specifications of those transistors and used a resistor on the base or gate to keep them from letting all the current through? It wouldn't work with a transistor but it would with a voltage gated component like mosfet?

Meh, been years since I tinkered. lol

 

[BobK]

You are missing the point. You cannot reduce the current while maintaining the voltage.

Bob

 

[Grazzje]

You are missing the point. You cannot reduce the current while maintaining the voltage.

Bob

Thats a really annoying problem, I half don't want to let go but I'm going to have to.Thank you so much for shining light on this issue.

I did a bit of research, it goes as high frequency sound is easier to block than low frequency sounds. I put the unit in a cardboard box and its a decent reduction.. Perhaps some 'convoluted egg profile' acoustic insulation foam will work spot on.

I have an OMRON solid state relay so I can work this thing on and off periodically. By using a much longer pipe, I can make sure there is always ozone present in the air flow during its off time.

Thanks again Bob, love this forum!

Grazj

 

[hevans1944]

Corona discharges are fun to play with. Perhaps the simplest solution to reducing the ozone production is to reduce the area available for the corona discharge. Maybe remove one of the two ozone-generating plates to reduce it by half and then attach some Teflon sheet material over some of the "holes" the ozone is created in?

 

[Grazzje]

Corona discharges are fun to play with. Perhaps the simplest solution to reducing the ozone production is to reduce the area available for the corona discharge. Maybe remove one of the two ozone-generating plates to reduce it by half and then attach some Teflon sheet material over some of the "holes" the ozone is created in?

Hevans you made the breakthrough for me, just run a test.

I just stuck some cellotape on the top plate and gave it a 2 second run. The corona on the cellotaped plate is reduced by around %90 but its still visible underneath the cello.

The idea is great. However, sticking the teflon down completely will be very difficult.

So I imagine I need something like glue. A very strong dielectric, fireproof, corrosion resistant glue. It doesn't have to be transparent but it has to be very tough.

Any thoughts? Or do you think, the arcing under the teflon will not cause any problems whatsoever. I mean what actually happens if the corona is isolated in a small space (under the teflon) and trapped away from airflow. Will it cause damage under the teflon secretly, without me being able to see?


I like the glue idea, let me know what you think Hev.

p.s Araldite is apparently temperature resistant, good chemical resistance too. But once I use it, there will be no going back. I guess I will have 2 plates giving me 2 tries at solving this problem.

Regards
Grazj

 

[hevans1944]

AFAIK Teflon cannot be glued by ordinary human beings. You would have to use a pressure plate to secure it, maybe use the corner posts and cut an aperture in the sheet of Teflon: Teflon backed with aluminum, stainless steel, or fiberglass circuit board material to hold it in place might work without arcing. I don't know what a continuous trapped corona discharge will do. It will get hot, certainly. Ozone is also highly reactive, so it may eventually break down the Teflon. Perhaps you could substitute polycarbonate (Lexan) for Teflon. But at least you now have a method to reduce the amount of ozone generated. The rest is just mechanics!

There are many ways to generate voluminous quantities of ozone. Ultra-violet lamps and high-pressure arc lamps with quartz tubes are pretty standard but arc tubes are a bear to work with. I like small, sharp, tungsten wires for generating corona discharges. You get a streamer of discharges in air that produce ozone like crazy. I forget what DC polarity works best, probably negative. Electrons are field-emitted by the intense electrical field at the wire tips and ionize air molecules. Some of these then combine to form O3 with adjacent O2 molecules. You can smell the ozone when it's working well. You can also play around with the other power supply lead, attaching it to a "ground" plate or cylinder enclosing the tungsten wires. You just need to avoid arcs, which a fast-moving flow of air can help prevent.

I have never used Araldite adhesive. But you might want to visit this link before trying to bond Teflon to anything. The ozone generating plates look inexpensive enough (US$26 with free shipping) to allow for "sacrificing" a couple of them in the name of scientific discovery.

Hop

 

[Grazzje]

AFAIK Teflon cannot be glued by ordinary human beings. You would have to use a pressure plate to secure it, maybe use the corner posts and cut an aperture in the sheet of Teflon: Teflon backed with aluminum, stainless steel, or fiberglass circuit board material to hold it in place might work without arcing. I don't know what a continuous trapped corona discharge will do. It will get hot, certainly. Ozone is also highly reactive, so it may eventually break down the Teflon. Perhaps you could substitute polycarbonate (Lexan) for Teflon. But at least you now have a method to reduce the amount of ozone generated. The rest is just mechanics!

There are many ways to generate voluminous quantities of ozone. Ultra-violet lamps and high-pressure arc lamps with quartz tubes are pretty standard but arc tubes are a bear to work with. I like small, sharp, tungsten wires for generating corona discharges. You get a streamer of discharges in air that produce ozone like crazy. I forget what DC polarity works best, probably negative. Electrons are field-emitted by the intense electrical field at the wire tips and ionize air molecules. Some of these then combine to form O3 with adjacent O2 molecules. You can smell the ozone when it's working well. You can also play around with the other power supply lead, attaching it to a "ground" plate or cylinder enclosing the tungsten wires. You just need to avoid arcs, which a fast-moving flow of air can help prevent.

I have never used Araldite adhesive. But you might want to visit this link before trying to bond Teflon to anything. The ozone generating plates look inexpensive enough (US$26 with free shipping) to allow for "sacrificing" a couple of them in the name of scientific discovery.

Hop

Good information here. Hevans don't get me wrong I would never in my wildest dreams believe I could glue teflon. lol. I was thinking of using only araldite as a big layer because the corona plate has 0.1 or 0.2mm high indentations on it, that bee-hive like structure seen in the picture. By sticking a teflon plate, we are still leaving those pores open to arc under the plate. If I used an adhesive, it would seep into those pores and better insulate the corona discharge.

Yes it would perhaps get hot under the plate. But if we attached a heatsink on the bottom of the plate, with some cheap thermal gel, the only problem left would be the potential corrosiveness of ozone itself.

The device is 50W. With losses, call it 40W. So thats 20W per plate? In terms of cooling challenges, should be an easy one.

To be honest I don't like the plates, tungsten wire would be much better.

So now, we have 3 outcomes:

1)Use the first plate with teflon or polycarbonate plates reducing surface area, screwed onto the device tightly with adequate heatsinks and active cooling.

2)Use some kind of glue (the picture is a stock picture, but on the generator I have, there is a big blob of white glue on each of the HV lines soldered to the corona plates. So that glue does have corona under it and it survives 2000 hours. It MUST be possible

Its deffinately got corona under it. Which glue is that? The plate is rated at 2000 hours so that glue must be able to last 2000 hours. It would be much easier than cutting and screwing a plate on. Big blob of glue.

3)Buying tungsten wire to create new corona discharge plates for the generator and propably using the same power supply (backup plan).


So I have 2 plates, one for glue, one for the plastic sheet. And if it all messes up, I can wind a tungsten electrode up.


Sounds good! Thank you for shining your bright light over here Hev

 

[Grazzje]

Hevans I disconnected one plate and covered half the other one with araldite epoxy resin. I was hoping it would generate 1/4 or %25 of the ozone or 2.5 grams per hour. What I failed to realise is that the power available would be %400 increased, on that area.

It starts arcing over the ceramic plate to the aluminium layer underneath it, from the side of the corona plate (looks cool to the eye) So the epoxy worked (at least in the short term) however the machine now has too much juice and is malfunctioning.

To be honest, if its arcing over itself at %25, even if we reduced this thing all the way down to %10 while keeping it durable, it would propably burn its own plate out because the plate is rated at 2000 hours... If its %25 surface area, and therefore about 4 times more power concentrated, it would burn the plate out more than 4 times faster I'm sure. 2000 hours is only 3 months anyway. At power like that this would be gone in days with the best DIY attempts ever.

I think the only way forward, is to build a custom ozone plate. Not plate based, but electrode based.

The biggest problem faced here is having the confidence to work this thing unsupervised.

Meh, project aborted. Here on, I would be better off buying a neon sign transformer and building the whole thing from scratch.

THANK YOU TO ALL for helping me on this project and I hope anybody reading can learn something from it

Peace out
Grazj

 

[hevans1944]

A neon sign transformer is overkill for ozone production. Try cutting the plate you Araldited in half with a ceramic-cutting abrasive disk. Use plenty of water for lubricant and cooling. Try out the smaller plate to see if it arcs over at the cut end. Your epoxy may not be a good insulator at high voltages. As for reducing the power to accommodate the smaller area... perhaps a few power resistors in series with the high-voltage lead will help. I would start with one megohm total series resistance (rectal extraction provided that value), maybe ten 100 kΩ 2 watt resistors in series. Decrease (or increase) number of resistors until satisfactory ozone production occurs.

The white blobs appear to be ordinary room-temperature vulcanizing (RTV) silicone cement.

The biggest problem faced here is having the confidence to work this thing unsupervised.

Yeah, stay out of the high voltage and make sure power is removed before making adjustments. Keep one hand in your pocket to avoid accidentally completing a high-voltage circuit across your chest. It's always a good idea to have a friend nearby to resuscitate and/or call for help if something untoward occurs.

Hop