Testing CO2 power supply

[pixpop]

I have a Chinese power supply for sealed CO2 tubes that I bought a couple of years ago, and haven't used. Now I'm finally getting ready, and want to test it without a laser tube.

Anyone have experience with this? I have a pdf with very sketchy instructions, that say not to operate it either shorted or open, so this means I will need to make a dummy load.

Would it be OK to just string a bunch of resistors together?

I'd like to get my control circuit designed and tested without requiring a tube and cooling system. I don't want to buy a tube until everything else is ready.

Thanks,

Neil

[zax15uk]

Neil,

You are dealing with extremely high voltage, at sufficient current to kill. Make no mistake it could be lethal. While open circuit it can easily arc to your cabinet or something else and cause severe damage. I don't recommend trying to run it without a tube in place. Good luck finding suitable resistors with a 22kV voltage rating (typical trigger/arc voltage), although Tesla coil resistors may work.

OK, safety warning over.

I'm not sure why it would be necessary to run the PSU at all, you can design the control circuit and monitor it's low voltage output without actually switching the PSU. Are you using an analog input or PWM?

Zax.

[pixpop]

Thanks, zax.

I'm going to program a microcontroller to handle all the safety interlocks and cooling system. It will also generate a pwm control signal for the laser.

If I put a string of resistors in series, they don't have to handle 22kV. E.g. if I have 100 of them, then each only has to handle 220 volts.

I don't understand why it would be bad to run the PS with no tube. What happens when the tube dies, or a connector falls off? Then there's no current flowing through it, and it's the same as operating with no tube at all. Are they saying that if the tube dies, the PS will be damaged?

(Yes, I understand there will be a tendency to arc, but my question is does it damage the power supply?)

But anyway, my plan was, that if my system is working for a while, and then stops working, I'll immediately be able to test the power supply and know whether the problem is with the tube or the power supply.


Also, I have a question about the power control (potentiometer or pwm): What does it control? The pdf instructions I have seem to imply that it controls current (rather than voltage), is that correct? Is it basically a constant current source with very high compliance?

Thanks,

Neil

[Sadheer]

How many watts of the power supply?

Sadheers

[pixpop]

Originally Posted by Sadheer How many watts of the power supply? Sadheers

Unfortunately, I've lost track of the original order. I seem to remember that it was for either a 25 watt or 35 watt laser. I'm going to bring it to work today so my Chinese colleague can translate the markings on the outside of the box. Maybe that will help, but I suspect they are just safety warnings.

[kewlkiwi]

Originally Posted by pixpop I have a Chinese power supply for sealed CO2 tubes.....Would it be OK to just string a bunch of resistors together

The manual for my machine (80w) includes this pic - showing a test setup for the power supply.

Also, one of the doc files I've accumulated (for a replacement PSU) says:

"5. Protection: with well-grounded enclosure, output circuit of power supply can be
open for short time (but arc between positive pole and enclosure should be avoided)."

This file is for:

"Product: HY-HVC02/X CO2 power supply for laser device.
Model: HY-HVCO2/X,” HY-HV” means family of high voltage power supply of Hongyuan Electric; “CO2” means it is for CO2 laser device; “X” means the length of laser lamp,X=1.2 means the length of laser lamp is 1.2 meter,X=1.6 means 1.6 meter, X=2.0 means 2.0 meter, etc."

Hope that helps!

[Tweakie]

Also, I have a question about the power control (potentiometer or pwm): What does it control? The pdf instructions I have seem to imply that it controls current (rather than voltage), is that correct? Is it basically a constant current source with very high compliance?

It just adjusts the current flowing through the tube and has no effect on the arc strike or run voltages.

Tweakie.

[zax15uk]

Originally Posted by pixpop If I put a string of resistors in series, they don't have to handle 22kV. E.g. if I have 100 of them, then each only has to handle 220 volts.

True...

Originally Posted by pixpop I don't understand why it would be bad to run the PS with no tube. What happens when the tube dies, or a connector falls off? Then there's no current flowing through it, and it's the same as operating with no tube at all. Are they saying that if the tube dies, the PS will be damaged?

The power supply shouldn't be harmed if it is truely open circuit, but there is a possibility it could arc internally (creating a carbon trace) or externally on the PSU itself and cause damage. In theory if the tube fails it won't be a problem.

Zax.