Anotherpower.com Forum
Renewable Energy Questions/Discussion => Automation, Controls, Inverters, MPPT, etc => Topic started by: Superscan811 on February 28, 2019, 06:58:17 pm
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Had an idea and probably not a good one,
BUT
Seeing that the main limiting factor for a transformer is heat, why couldn't you use copper tubing, instead of wire, in a transformer?
When the "coils" start to get a bit too warm, circulate a bit of water through them.
You would need to replace the standard fan with a fan/radiator/pump, to cool the tubes during use but it would make for a more compact transformer you would think.
Also, you could get away with the minimal amount of primary windings, as the tube wouldn't be getting as hot.
Thoughts???
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If it were possible, the cooling potential would be awesome
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Many years ago I worked on water cooled electric motors. They were cooling water pumps for power stations. They were wound with pvc coated wire, stranded to be flexible. Water was circulated through the motors and windings to cool them. For their size they were very powerful.
Also some air conditioners in large buildings circulate refrigerant gasses through the windings to cool them, same thing small motor large horsepower. One I saw and worked on would have been around 60 to 100 hp if it were air cooled but was actually 500 hp because of having freon cooling.
Your idea of tube would work, winding the transformer would be problematic. Possibly just the low voltage side could be tube which would also cool the hv side.
Have fun
Pete
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They also make water cooled TIG equipment. Water cools the power cable, then torch head, then returns to rad/fan
via a separate tube.
Used to use one to weld aluminum
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I think a cooling system made for desktop cpu coolers and wrap the outside of the xfmr, wrapping through the hole in the center May invite trouble damaging wires and characteristics of the xfmr, wrap with 5/16-3/8” copper tubing. Find some heat sink adhesive compound (eBay, Amazon)so that the tubing makes positive contact. The adhesive does not set up hard but is flexible and should be able to allow you to remove it later if necessary. Maybe wraps some Mylar tape first. Make sure that the copper tubing connections are made outside the inverter just in case of oops!
The cpu cooling kits are closed loop so I think that’s best really. Another recommendation would be to make your tubing coils on a metal can or piece of wood the same diameter thus avoiding possible damage. I do this with refrigeration coils when I need a consistent coil wrap.
Good luck!
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The really big ones they just immerse in an oil bath. Crude but very effective.
Some of the hydroelectric installations I did a bit of work at, used hydrogen for cooling. Its low density meant it didn't impede the machine (probably helped!), but evidently hydrogen can carry away a lot more heat than air.
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The hydrogen is primarily about drag, while leaving everything "submersed in a cooling fluid". It's not particularly efficient per se vs air, just has better heat transfer to viscosity characteristics, and of course doesn't create as much heat of its own in turn.
And yes, agreed on the oil. Mineral oil has very good characteristics for this. Cheap, readily available, excellent electrical insulation, thermal conductivity, boil/freeze/smoke/non-toxic/etc qualities, and is a go to for anywhere heat needs to be taken away efficiently from electrical equipment that is sensitive to air contaminants and requires near zero maintenance.
Hit Big G images up for "aquarium computer" for how this concept can manifest in the DIY department... Half of them even leave the fans in there in some form as "pumps" ;D
Just... Bring a mop... Lol
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The hydrogen is primarily about drag
Well, not really...
"Air, water and oil have all been used for cooling. But hydrogen's low density, high specific heat and thermal conductivity make it a superior coolant for this application."
and
"Hydrogen gas is 7 times more effective as a heat transfer medium than air"
(Also 1/14th the density, which is an added bonus!)
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Ah yep you're right on that Ross. Mix of 2 ideas got me here... Confusing sp heat of hydrogen/helium combined with having been told however long ago it was mostly because it put up next to no fight for moving parts...
That said, I'm still twitchy about the idea ever since first hearing about it... I'm not a fan of having hydrogen around in any quantity... And I guess neither are they but it obviously has advantages or they wouldn't use it lol... It's only even for these reasons that it even stuck with me as a concept :o
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I had thoughts of water cooling a transformer a while back, too. Heck, just dip the whole thing in a big bucket of water and fire her up. Bring the wiring out the top. Pump the heated water over to a radiator of sorts, release the heat and recirculate it back.
Yeh, yeh I know, crazy right? But wait. What if I said let's use distilled water -- a non conductor. One problem I saw was the need to keep the water from the metal core material (rust). Maybe encapsulate the whole transformer in epoxy?
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Hi Sunnypower, Transformer oil is a much better option.
No problems with rust.
Doesn't conduct electricity
Can use convective cooling. Just look at large transformers the pipes up the outside are so that the warm oil will cool as it rises through the tubes.
Been around a long time and works a treat
Cheerio
Pete
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>Pete: I certainly agree that oil-filled utility/industrial transformers have proven themselves in the field. In such an environment, water cooling, in any form, would be impractical.
On a smaller scale (inverter torroid), water cooling an epoxy capsulated transformer seems practical and relatively inexpensive.
Has anybody out there actually tried it? I believe water is a better, faster conductor of heat than oil; meaning the system could be more efficient and smaller in size. I question whether oil cooling would react fast enough to control heat build-up in an inverter torroid that is suddenly pushed to its limit.
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Hey Sunny
Mineral oil is not much diffufrom transformer oil and fairly inexpensive. I just wouldn’t want to find out that some worker had made a mistake with the epoxy or the epoxy has cracked. Just find an inexpensive cpu radiator, pump and hoses, put the tranny in a large Tupperware with mineral oil. Not baby oil, it has thing added that may conduct electricity. You might even get creative and make it so you can fit a lid on it and put it back in the inverter. Use 2 miniature radiators or peltier setups I’ve seen lately. By the way the radiators come with fans if you didn’t know. If you can run an extremely fast hot running desktop In an aquarium full of mineral oil for weeks and the only problem encountered was a leak in the glass that’s a winner to me.
My 8000w will run 3200w-ish for several minutes and the tranny never gets “hot” your going to have to trick it into giving you more watts. I believe now they have some pots on the board so you can adjust voltage and maybe wattage. Otherwise it’s bypassing the CT so it will give more watts.
Good luck
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Yes, you're putting so much at risk with water with no practical gain.
Also, if the containment scheme is large enough, you don't even need radiating elements. I've even done this with air in smaller equipment, circulating internally, sealed to the outside. Your primary goal (other than the obvious) is to simply increase the cooling surface area with a suitable medium, in this case a liquid. If your transformer isn't marginal, you don't need anything but a liquid tight box to put it in.
Also, any "potting", epoxy was mentioned, would only serve to work against your goal if it was thick enough to make me comfortable enough to use water. Just go oil and save the headaches.
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OK. Some interesting and informative material being offered.
To continue, a couple of follow up points, whether it be oil or water: I'm not sure immersing a typical OEM PowerJack style torroid into either oil or water is a good idea. It was never designed for that environment (think glue, adhesive, wire coating). In theory, either distilled water or mineral oil could serve as a safe, non-conducting medium, though. Off the top of my head, I'm thinking an epoxy coating (2-3mm) should be a decent thermal conductor; so probably not a design impediment.
Then it occurred to me, why aren't we using mineral oil as a coolant in our cars. Doesn't deteriorate, no problem with metal rusting, won't freeze. Long term thermal transfer OK, short term, not so much. Given how quickly these small torroids can heat up, I would think oil is not the best choice. Just a guess, offering no proof.
I personally have no need for liquid cooling, but as to practical info on enhanced air cooling - - read on.
I've been using two PJ8000-24s (2016 version) 24/7 for the past two years where I modified the cooling via enhanced airflow.
Opened up the torroid core to let it breathe, tilted it on to its short side, added a 235 cfm fan to blow through the core in wind tunnel fashion. No need to change any wiring lengths, just some careful bending of the primary wiring. Needed to add a 2 x 18" metal piece on each side to support increasing the case height. The torroid sits on two short lengths of thick wall 1/2" id silicone tubing, currently unsecured; but gravity is my friend.
Heat be gone! This behaves like it could run for hours at 3500-4000 watts, if you've got the continuous 165A to spare from your batteries. I tried 20 minutes at 100A and was then able to grab on to the torroid and hold on for 5 seconds before having to let go. So, pretty scientific measurement . . . . .
Bought a third PJ8000-24 as a spare (late 2018, the new look case with replaceable daughter boards). They added a top mounted fan mostly centered over the torroid. Unfortunately, the torroid core is still is still blocked by the mounting solution they use. From their standpoint, its the only practical way to do it for shipping reasons.
If you need more cooling, though, it's easier to do with this new model. Just remove the mounting bolt and top/bottom core cover pieces to open up the center. To go a step farther, fashion some metal air deflectors to enhance the airflow pattern around and through the torroid. While not as effective as my wind tunnel design, I'd expect you'd see noticeable cooling improvement.
At some point I want to try supplying the inverter air input with cooled air via an evaporative pad during my hot, dry summer season. Could cool moist air be the reasonable compromise in this discussion?
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The words moist and electronics together made me cringe. Cool dry air is always best. Try hunting thru thrift stores, flea markets Ebay etc for the smallest dehumidifier you can find. Refrigeration and HVAC is just one of my expertises. Dehumidifiers are just low btu air conditioners. The could build some flexible duct to the evaporator side to the fan intake. Be sure to duct the heat side outdoors or your defeating the whole process. The fact that the moisture is condensing on the evaporator means that heat is being drawn away and air is cooled. Normally btu In cancels btu out just allowing for moisture removal. This is why you want duct the condenser coil heat outside.
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The big thing with water is that while it may start out non conductive, the moment it makes any kind of contact with any metal (and really much of anything that can dissolve in it), it becomes conductive. This is why it's not used.
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My first thought re using a dehumidifier was that they aren't really designed to put out cold air, just remove moisture from the air.
To cool the torroid, I need cool air and a lot of airflow (235 cfm). While an interesting idea, modifying a small dehumidifier to get me there seems like it would fall short. Maybe a 5000 BTU room AC appropriately modified to direct the air where needed could do it, but the penalty is probably 700-800 watts from the inverter output.
I'm thinking if I keep the relative humidity off an evaporative pad under 60%, I'll be OK. I believe the PJ is good to at least 85% RH. Summer in the SoCal inland areas sees humidity in the 15-20% range. It's pretty easy to get a 15-20 degree F temp drop by misting a cooler pad.
When the outside air and garage gets to 105F, I'd be happy to put 90 degree F air into the inverter located therein for a few hours. Obviously, I don't want water droplets getting into the inverter. And I haven't run any numbers to see what temperature drop correlates with a 40% increase in humidity off the pad. My goal may not be achievable.
Regarding the torroid in distilled water, I hadn't considered that reacting with metal might change its non-conducting properties. If we adequately encapsulate the torroid and attached wires somehow, I guess it really doesn't matter. I drop a small submersible AC outlet plug-in pump into my pool spa when it needs to be emptied. Haven't blown any breakers or tripped a GFI yet. Given the moving parts, that would seem an even greater isolation challenge. Yet they manage to get UL certification.
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they are usually double sealed and oil filled
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My pj is in a room with a window set at 30c and the fan on constantly. Earlier this week I had my daughter’s boyfriend add the 5v6 zener for battery level and a cheat for the ct to allow higher wattage. This added nearly another 1kw to just below 4 kw and it hasn’t shut down due to toroid overheating.
Of course I have helped my daughter to design a schedule to manage use wisely since I’m 10,000 miles away.
My 15kw has 24v fans and they scream and push a lot of air. One was a regular 3wire computer fan for the toroid but I slid that next to the toroid and put a 24v from Amazon in place. Maybe all you need is simply get a fan that’s the same voltage as your battery bank. An example would be:
https://www.amazon.com/gp/aw/d/B077GJNMYP/ref=ppx_yo_mob_b_inactive_ship_o0_img?ie=UTF8&psc=1
It’s 185 cfm and I assure you when I put another one in my 8kw our housemaid quit sleeping in there.
I love to experiment and have bells and whistles but sometimes the k.i.s.s. System is best also.
If your experimenting great, but please don’t tempt fate with water.
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I really don't need to make any changes to my PJs at this point. They do OK in the heat of summer because my microinverters cover the heavy daytime loads. I've got enough extra microinverter output to push back 80A (2000+ charging watts) through the PJ that's mostly dedicated to battery charging. That drops off linearly over a three hour period in the morning before it gets too hot outside.
My Morningstar dump load controller manages FLA battery charging. Does a great job keeping the battery voltage below the PJ's upper limit. Haven't needed the Zener diode mod.
A further attempt at extra cooling would merely be to extend equipment lifespan/reliability. Whether the cost to benefit ratio is favorable is certainly in doubt and I don't underestimate the value of keeping things simple. Often it's best to just let things be. Is there anyone who hasn't learned that lesson the hard way?
I don't need anything close to 4000w from my PJ; but if you've got the battery juice and enhanced cooling, I think 4000w continuous is achievable - - for anyone following this discussion who might have the need.
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Hey Sunny,
Very well said. Hope you didn’t feel I was harsh. The whole thread got my brain thinking of ways to experiment. When I go back to the Philippines I’m bringing a monster pj that I’ve managed to make much more efficient. So the 8kw will be there to play with. I have spare coils boards and mosfets.
I often think about micro inverters and charging. My 15kw is minus the charging board but the 8kw has charging. I ended up with 5.3kw in panels. After spending 5grand on lfp’s not sure if it’s cost effective to spend that money. I would need iq7plus and the envoy with software. Then there’s the landscape wire right? Grounding, no ground there so install a grounding rod that I never can seem to get to.
Well it’s a thought.
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Somebody correct me if I'm wrong, but when using any PJ for back charging batteries from micros; no internal charging circuit is needed or used.
Just connect the total micro output to the PJ output and the micros send the power through your PJ to the battery bank or to your loads. If included on your PJ model, never make any connection to the charging input connections. The micros go to the PJ output to provide the "local grid" which turns the micros on. In this mode, nothing in the PJ prevents overcharging your batteries; however. You have to do that externally via a dump load controller.
I've been using IQ7 plus micros for nine months. They pair well with PJs. You don't need the Envoy monitoring to make the system work. It's all pretty plug and play. Just make sure the micros you buy are preset for your country's power.
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I see what you’re saying. My 15kw has a board inside that’s labeled charging board and the board is not present where it would plug up in other models. Control boards are a complete re-engineer. My 8kw says off grid and I never bothered trying to tie to the grid. I have a ATS that switches to grid when the pj drops out. The pj has a plug for charging but I didn’t see any need for it. I thought if I switched to micros that I would us a 24v 80a intelligent charger or build a a larger one at a higher voltage and current and feed that thru one of the mppt chargers. My current issue is that out of 5.3kw of panels the charge controllers are showing at high noon only around 3.6 to 3.9kw between the two sets. They are set 3 in series for 108v 300w each 3 sets paralleled front roof same on back roof east west orientation. One controller always shows more kw than the other. PV voltage will be the same at noon but the kw will be high on one low on the other. Bad connection? The installer connected more sets on one than the other?
Would micros take all this guess work out of it? As long as I can charge a full tank and run the house?
Hmmm?
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If you want to try micros with your current setup, maybe this approach: Take one group of three series panels out of the parallel configuration. That should allow your current system to work OK at reduced output while you experiment.
Then wire up one (or three) micros to the panel(s) and connect to your PJ8000-24(?) OUTPUT. Fire up the PJ and five minutes later the micros will start producing power. This solar power has to go somewhere, either into the attached loads on the PJ or back through the PJ into your battery bank. It's magic. The micro power output just goes where it needs to go. But, you do need external hardware to protect the batteries from overcharging as part of the total system design. For short periods under supervision, you could test the system without the extras.
If you want more expertise on how to do this, I'd suggest starting a new subject so more in the community can weigh in. We're getting off track on the OPs original subject. Be sure to present the big picture of your current setup and what you ultimately want to do.