induction heater failure in humidity / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

induction heater failure in humidity

1 2 next

Move Thread

LAN_403

IamSmooth

Fri May 27 2011, 02:02AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

my induction heater was in high humidity and I was cooling the Celem capacitor and mosfets with iced water. I had condensation dripping all over. eventually some water got between the exterior bars of the capacitor that are used to connect the hoses. A short resulted.

How do I deal with the condensation? I've sprayed my board with Shellac. I'm planning to do the same with the capacitor, or dip it in paraffin. Is the approach reasonable? How do industrial units deal with condensation with the cooling units?

Inducktion

Fri May 27 2011, 03:09AM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

I'd use a dehumidifier...

Or, cover EVERYTHING with something, to prevent condensation from creating shorts. I don't know what else can be done.

IamSmooth

Fri May 27 2011, 04:33AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Dehumidifier is not an option for the environment the unit will be used in. I am open to ideas that others have used to deal with high levels of humidity, or what is done in the industry when there is high voltage and humidity.

Dr. ISOTOP

Fri May 27 2011, 07:28AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

You're not supposed to be cooling your components to below ambient, seeing as they are spec'd to something like 80C.

Ash Small

Fri May 27 2011, 09:32AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Maybe a non-conductive coolant? Pure ethylene glycol? fluoro-inerts might be a bit extreme here. oil might do the job.

ConKbot of Doom

Fri May 27 2011, 11:30AM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

PC guys like neoprene all over everything around the CPU socket when they do the crazy DICE/LN2/phase change stuff, and depending on how easy you need to access stuff to service it, something like RTV could work. Or if you want to make sure it doesnt stick, use something like

, and mix it up, mash it in good, and let it cure, if you need to get into the stuff later, you should be able to peel it off. $40 for the trial size is a bit pricy, but they are decent sized containers and you wont need a ton of it. The stuff you peel off to access the electronics would retain the same form, and you could probably just put it back down, since you just need it as insulation to keep the humid air away from the electronics, not for sealing.

IamSmooth

Fri May 27 2011, 12:20PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Ash Small wrote ...

Maybe a non-conductive coolant? Pure ethylene glycol? fluoro-inerts might be a bit extreme here. oil might do the job.

It's not the water coolant that's the problem. .It's the condensation that is the issue.

bwang wrote ...

You're not supposed to be cooling your components to below ambient, seeing as they are spec'd to something like 80C.

We were testing it in a blacksmith's shop that is open to the outside. Ambient temperature was about 95F. I don't think I want to operate the mosfets at this temperature.

So, is industry using very cold coolant, or is is using 70F fluid? Even the latter would have caused a significant collection of condensation on this day given the 100% humidity.

I do have to say that I had an ultrafast fuse set at 50A that saved two out of the four mosfets, and left the circuit board completely unharmed. Without this fuse I would have lost everything. I will have to take a picture and add it to my tutorial page.

Fraggle

Fri May 27 2011, 01:44PM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

put the whole sub-ambient section under oil

Dr. ISOTOP

Fri May 27 2011, 02:07PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

IamSmooth wrote ...

We were testing it in a blacksmith's shop that is open to the outside. Ambient temperature was about 95F. I don't think I want to operate the mosfets at this temperature.

35C is nothing to MOSFETS so long as you derate appropriately; i.e. if they weren't scorching hot to begin with, a 15C rise in ambient should matter too much.

ConKbot of Doom

Fri May 27 2011, 04:14PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

<- overclockers method of condensation prevention explained with pics

But as stated, sub ambient cooling may not be needed, how hard are you running the mosfets, and is your water cooling high flow or low flow? in a high flow, the temp difference from inlet to outlet isnt that much, so ambient temps for the radiator could be fine, where a low flow may take in 40F water and spit out 90F water, (or 95F and 145F in your hot environment), and items being cooled by the water thats hotter might be overstressed, so if ambient water wont do the job, up your flow rate and run with a closed loop system.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob