AC_Hacker, I will probably look into a better speed control. Perhaps, once I build refrigerator, or something like that, I will be more interested in variable speed. I am mainly interested in the small size, and at 80 watt input power, I don't need to turn it down anymore! An electronically controlled feedback loop that set the speed to match the load might be fascinating, but beyond my level of interest at this time. Another idea for the variable speed, is to give the operator of say, a refrigerator, some information about the power consumption of the unit, along with the run times and duty cycles; they could then turn up or down the the compressor speed, depending on their desires to gain efficiency or for faster cool down. Most people probably wouldn't care, but I think it would be neat.
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Originally Posted by TechShop
That sure is a neat little unit.
It looks like the board that comes with it can run a complete system including the fans.
That must have an original application in RV refrigerators, portable coolers, etc.
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Yes, the board will run a condenser fan, evaporator fan, accept some digital signals for run speed, has a temp sensor for compressor overheat, has a shunt for overcurrent protection, and of course has the little pot for manually adjusting speed.
I don't know of too many appliances that are using these compressors specifically. I've seen some pics of appliances that include refrigerators, freezers, dehumidifiers, portable refrigerators, liquid chillers, and more.
The company Purswave makes a very similar compressor to the one I have; so similar that it may be the same manufacturer, I'm not sure. Here's some of the products they make. Some of the compressors are larger, but many are DC.
Refrigeration Appliance -
Compressors this small and smaller, are being utilized a lot in personal cooling for people who must wear environmental protection suits of some sort. The US company Aspen has a military contract to produce tiny 1.9 cc rotary compressors for this purpose.
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How are you detecting oil migration??
-AC
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So, the oil thing is interesting. I don't have much experience changing oil in hermetic compressors; by that I mean none. I wasn't sure how much oil was in the compressor from factory, so I emptied it and charged 50 mL of POE with a syringe and needle. The copper lines I brazed on the compressor were going to make it difficult to check the oil level at a later time, but I figured it out. I utilized flare fittings in my system, since it is experimental, and they allow me to make quick changes, or do things like check the oil charge in the compressor.
The first time I pulled the refrigerant charge out, a good bit of oil came with it, from the suction line. I unhooked the compressor, an flipped it upside down. To force the oil out of the discharge line, I had to force air into the shell with a piece of wire insulation stuck to the needle of the syringe. Measuring the remaining oil, I found I had lost about 10 mL of oil; probably not enough to cause damage, but definitely oil migration. How this might play out in the long run, I don't know.
I have since moved the suction service valve, and I find I do not lose as much oil when recovering refrigerant. Whether or not it is returning to the compressor during operation, is another question. I must look into oil retun methods like traps, and wicks.
That is all for now, time for dinner.
Tomorrow night, I'll be adding some features, and nailing down the proper length of capillary tubing.
-Marx