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Everything posted by InPhase

  1. It seems like with all the money spent with boost converters and cordless tool batteries and blow ups and melt downs that you could have just bought some batteries to make a 36 or 48 volt system. A golf cart place near me has a special offer for six Crown 205 Ah 6 V batteries for $655, which would get you 36 V. Or six Crown 165 Ah 8 V batteries for $815, which would be 48 V. Don't get me wrong. I'm all about cobbling things together, but I don't have any critical needs. If I did, I'd bite the bullet and get a good set of batteries and a charge controller as the foundation of my system, and then cobble on top of that.
  2. Windows 98 was a pretty good OS which was destroyed by windows ME. Then Windows XP was awesome, after a couple of service packs. It was too good. It just kept going and going. MS learned their lesson. Never again would they make such a sturdy and long lasting OS. XP still runs my CNC machine. The source code has been leaked but it would be nice if MS would officially release the code so that the amateur community could construct a truly great Windows-like OS.
  3. You can get a decent used molded case breaker on eBay for cheap. I wouldn't use a second hand breaker in a contracted job, but for myself, I would risk it. Here's a 400 amp 2 pole breaker with a 250 VDC rating https://www.ebay.com/p/1428853619
  4. Half the volts means half the amps, which makes it 1/4 power. Use Ohm's Law.
  5. Plenty of smaller wires can indeed handle 300 amps for short periods. But to be in compliance with the standards of permanent electrical wiring, the NEC size is it. Most fuse holders of that size will have a bolt stud connection, meaning you use a ring terminal or mechanical box lug of the appropriate size. I personally would size the wire to the maximum continuous load likely to exist. Size it for that load and to minimize excessive voltage drop at temporary peak loads. For example, if your long term load is 150 amps, you could use 1/0. But at 300 amps, the voltage drop might be excessive, so you might use 2/0 or 3/0 instead.
  6. As far as wire sizing, if you're in the United States, the only source you need is table 310.15(B)(16) of the NEC. It is a good starting point as well as legally enforceable.
  7. There is no such thing as good AND cheap power electronics. You either pay high prices for reputable names, or build it yourself. Cheap charge controllers on eBay can be hacked into decent operation, but it doesn't come out of the box worth diddly and it isn't plug 'n' play.
  8. You can run it on 120 volts and it will use 1/4 the power as it will at 240 volts. But ultimately you won't save anything because it takes the same amount of energy to heat a gallon of water to a given temperature at 500 watts or 10 million watts. What changes is the time that it takes.
  9. The magnetic flux is completely contained within the toroid, at least theoretically. Other types of cores have much greater flux leakage. A toroidal transformer is just about as good as the laws of physics allow a transformer to get. There is only one phase, split in half to produce two voltages. Tying two single phase transformers together still makes a single phase. It is basically what is already going on in the standard transformer: Two transformers on the same core joined together in the middle. I think you'd actually lose something by having two separate transformers because you now have two primaries instead of one. As far as autotransformers go, they are quite a different beast. Autotransformers are a lot more efficient than regular transformers because energy is transferred by conduction as well as induction. For a given size, an autotransformer can be much smaller for the same kVA. But they aren't electrically isolated between input and output. It's just too easy to accidentally put an unintended voltage somewhere it shouldn't be with an autotransformer.
  10. Why not just go straight for the liquid nitrogen coolant loop? He could wind the transformer with a superconductive material and power the cryo equipment straight from the inverter. Also make the core 3 feet wide and 9 inches tall to reduce the stress on it.
  11. Yes, 4 identical breakers riveted together that have a spindle between them to trip them all simultaneously. It isn't just a handle tie. As far as MakeSkyBlue, who knows why the Chinese do what they do. I never owned one, but my now-stolen Epever 40 amp controller had terminals that fit #6 with room to spare. I have a bunch of wire pin reducers that I use when the wire is too big for the terminal that I would crimp on otherwise I suppose. The 6-2 MC from the wholesale, the THHN from Home Desperate, which, unless you're buying thousands of feet, has the best small wire prices. The wholesale can't touch it below 10000 feet. Loss leader etc. You've got some great pricing in these times of skyrocketing materials, or you're buying a chit ton of it. What's lumber cost for you?
  12. I'm guessing you guys haven't bought wire in a while... It's through the roof. The highest I've ever seen it, and I've been letting the smoke out of stuff for a long time🤣 I bought 200 feet of 6-2 MC cable Wednesday for $1100🤬. 500 feet of #12 stranded THHN is over $100. 12-2 Romex was $55 for 250 feet a couple months ago is now $125. It's insanity.
  13. As far as code goes, it doesn't allow paralleling smaller than 1/0. I personally would parallel #10 temporarily until I jiggered a better way. The parallel breakers making up a 200 amp main is different than just using 4 individual breakers because the main will have an internal common trip mechanism. It would probably be best to have a set of lugs sized for a single wire that will handle the full load.
  14. You can try what is called a "hard start kit" on most capacitor-start motors. It is just a bigger start capacitor.
  15. How do people in Arizona install standby generators if they aren't allowed to use a transfer switch?
  16. I have had success protecting circuit boards in damp areas by spraying them with a couple of coats of polyurethane. Start with a light mist coat and let it dry. Then lay it on progressively thicker letting it dry in between coats. If heat dissipation isn't too much of a problem, a NEMA 3 PVC box with a gasketed cover and proper cord grip connectors and silicone works great.
  17. Sir, doubting something the talking head on CNN said about the virus makes you a racist. And there's two things I don't tolerate around me: 1) Racists 2) The Irish
  18. I've done enough roofing to know that it sucks. Besides, I'm not much of a drunk, so I'd never fit in anyway.
  19. What a degree really signifies is that you can sit quietly for years and do what you're told. Unfortunately, most states in the U.S. require some kind of school work in order to offer engineering services. But, a company could certainly employee someone in an engineering role without a degree.
  20. Oh, I just figured you worked as an engineer at a firm somewhere or had your own shingle out. Is the McMansion building a full time gig, or is it just to keeps the bills paid between gigs? I personally am very ADD/ADHD and can't hold a job working for someone else. Not very long anyway. So I've been self employed for going on 20 years.
  21. You mean Sean doesn't have you on full time!? What is your normal job, if you can divulge such info?
  22. I don't think you have much to worry about. Moving reactive current around in your own system costs just about as much as not moving it around. But if you're worried about it, start up a big induction motor to balance it out.
  23. Re: FET resistance vs. load. You are absolutely right about the longer pulse widths. At low load the FETs stay in the linear region longer but the current is minimal. Down to the magnetizing current. However, at high load, they burn watts like a power resistor. Somewhere in between there is an optimum balance where a maximal amount of current is flowing across a minimal voltage drop. Below and beyond which it is more wasteful, and has no obligation to match the transformer maximum efficiency point. Drive and signal problems not withstanding.🤣 Transformer efficiency is pretty intuitive. At zero load, it is still burning watts with magnetizing current. It is 0% efficient at no load. It can only get better from there.... To a point. At some point the resistive losses and steel losses shift the slope the other way. So, like the FETs, there is a point between no load and smoking hot where a maximal number of watts is dissipated in the secondary load with a minimal number of watts wasted in the core. If I were a shady corporate inverter manufacturer, I would find the narrow region where both of those quantities are optimum and use that as my efficiency statement. And if I were a shady Chinese government sponsored manufacturer, I would completely make up a wattage for a substandard inverter and then claim it was 99.99% efficient at 210% load.
  24. I would imagine that there is a "sweet spot" in the efficiency of any inverter. Transformers are most efficient when loaded to near their capacity yet the FETs go down in efficiency with more loading. The point where the lines cross on a graph would be the optimal efficiency. Manufacturers likely state the efficiency at the optimal loading point vs maximum loading.
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