Three Phase Power


Daisy, Daisy

The other day I mentioned that my new convertible runs on three phase electric power. We don’t have 3-phase power here at the farm so what’s a body to do? The electric company wanted $50,000 to upgrade us to 3-phase power because we are a mile and a half out from the main line. That’s a bit too much for my budget.
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We don’t need three phase power often but when we do it makes a big difference. The three phase power makes motors run more smoothly, efficiently and they last longer.

The solution suggested by Bill Powell is a phase converter. So in addition to the combination scalder dehairer, which is the most powerful piece of equipment we’ll have in the butcher shop, I will be getting a powerful phase converter to take our single phase power up to three phase power. Thus I’ve been learning about wiring 3-phase power and working on picking out a rotary phase converter.

There are several different kinds of phase converters and it appears that the rotary variety are better than the digital phase converters. But even there it appears that not all rotary phase converters are created equal, based on reading the literature from the various companies and looking at their warranties.

I’ve googled but not found a lot of real person reviews. I do not count PR snarks leaving fake reviews. I have found a lot of corporate spam about their products – sour taste in the mouth that leaves. Google is polluted well and good.

If you have experience with these beasts I would be delighted to hear from you. So far all I’ve found is manufacturer claims as to why theirs is better and why their competitors produce junk. Real world experiences from other users would be great. If you know of any forums where people have discussed these pointers to them would be appreciated too.

Outdoors: 73°F/57°F Cloudy
Tiny Cottage: 69°F/65°F

Daily Spark: The “Greater Good” is a greedy lie propagated by the powerful against the weak.

Bill Powell is the head of Washington Electric Coop and no relation to Mary Powell head of Green Mountain Power. Both names appear to mean fount of power… Both are presidents of electric companies. In the same state. In a small state. Hmm… That is just too much a set of coincidences. I have a long list that I have gathered of names like this. Evidence is gathering that we’re in a Dirk Gently novel. No conspiracy – just amusing.

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About Walter Jeffries

Tinker, Tailor…

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17 Responses to Three Phase Power

  1. Marilyn says:

    Hubby is an electrician for many years, has done cannery & Gov work in Kodiak AK. So he says a phase converter rotary is the best. An alternative to a phase converter is a variable frequency drive for each motor. These are better for the motor and power consumption on start up. They are more efficient if the largest motor is not used often. If there are more questions email & I will quiz hubby. He does not use computers much!

    Marilyn

  2. mellifera says:

    Good ol’ Dad the Nuke Engineer might know something about this one. Or not. I sent him your link, we’ll see if he’s able to come up with anything.

    • Oh, just the person to ask! Please do.

      Apparently there had been a rumor going around at one point years ago – I didn’t start it – that we were building a nuclear power plant up here on the mountain. The way the story was told to us is that at the one town meeting we missed in the last 20 years someone stood up and asked something to the effect of “What are we going to do about those Jeffries and them building a nuke plant up there on the mountain!?!”

  3. Adam Stevens says:

    Walter,
    I’m a commercial electrician in real life, farmer all other times :-). I have a little experience with both ‘add a phase’ and freak drives. My understanding on the freak drives, is that each motor would need a separate drive, and that might not be possible with a ‘factory’ unit. (I am surprised that on a custom piece of gear they can’t build it with single phase (240v) motors, even if it bumped the cost 15% that would be cheaper than the utility cost, or a phase converter, or freak drive) Although my experience with phase converter’s is typically after they have failed, I would agree that the rotary seem most reliable. I guess the only other question I would ask is if you have the available power to run it (as it will take more than it gives)…

    • We have 200 Amp service and use very little of that right now. In fact, we used to have 30 Amp service and used very little of that. Most of our load is our chest freezer and then when we have to heat water for cleaning equipment on the farm. Thus most of that 200Amps is available. I was told that was plenty, that the machine uses 60Amp breakers. Hopefully this proves true.

      The manual for the dehairer just arrived by email. German words, of course but we’ve got Google so now I’m learning German said Werner von Browne.

      I think it may the the high initial starting torque of the three phase motor that they’re looking for. Flipping 550 lb pigs takes a lot of muscle. I saw Hagrid do a big pig but I won’t try.

      Heizung: 15KW (that’s the water heater)
      15KW ÷ 240 VAC = 62.5 Amps

      Walzenantrieb: 2.2KW (that’s the rotating motor that tumbles the pig in the washing machine)
      2.2KW ÷ 240 VAC = 9.2 Amps

      Hmm… yet they are drawing both of those through the same plug and only requiring a 60Amp circuit breaker. Looking at the wiring diagram they might be turning off the heater element when the motor is running. That helps with power management. It also explains why when the machine is run hard and fast the water temperature drops as I saw happen at Adams.

      Einspeisung: 400VAC (supply voltage – they modify it for us 240VAC60Hz Americans)

      This gives 17.2KW total power consumption. That’s about 143 Amps off of our 200 Amp service.

      Convert that to horse power by dividing by 0.74 and we get 23HP.

      If I allow a 50% overage (reasonable?) because getting the motor started is hard then we get 35HP for the rotary converter. The next closest size up is 40HP.

      Back to amps that means 40 ÷ 0.74 = 54Amps at 240VAC to run the rotary phase converter at maximum draw plus inefficiency in the rotary phase converter.

      Since the majority of the load is the heating which could be simply done on single phase I asked them if they could split the three phase motor from the heating elements with two cords. The answer was that it was difficult. Looking at the wiring diagrams I see why – they’ve balanced the heating elements over each of the three lines – which makes sense if you have three phase power available from the utility. It would be really nice if they offered an option where the loads are separated for customers like us who must generate that third phase since single phase is all that comes from the utility.

      So now the question is how much extra energy is it really going to cost to run the rotary phase converter.

      A phase convert powerful enough for this costs $3,000 to $5,000.

      David’s suggestion of the PTO or other generator for when we need three phase is an interesting one. I saw one for $2,000. Then there is wear and tear on the tractor. I’m looking into what a three phase generator would be like too. I had planned on getting a generator because we get a lot of power outages, especially in the winter. Perhaps a three phase generator would be the best solution. Some of them even run on diesel which can be made from pig manure and pig fat or on propane – methane can be made from pig manure too.

      Thoughts are appreciated. Check the math above.

      • John Barlow says:

        What sort of motor is used ?
        The only reason for 3 phase is to drive motors, if it is only balancing the water heating across 3 phases that coul be converted to single phase (simple re-wiring) – no extra cost involved. If the motor is actually using 3 phase, and it only uses 2.2kw then you could swap the motor over to a single phase unit. least cost, simplest solution ??

        • Converting the resistive load (water heater) to single phase is easy but from looking at the machine specs I think the reason they have the three phase on the motor is to deal with the high starting torque when it must throw a 550 lb pig up in the air at the beginning of the wash cycle. An alternative would be a soft start on the motor.

          The problem is the machine comes with a one year warrantee and costs $40,000. Ergo, I’m hesitant to start hacking it before it is out of warrantee.

          The simplest solution may be a three phase generator. We need a generator to backup our refrigeration during the critical 18 hour pull down period immediately after slaughter. That same generator could also act to provide power during dehairing which would give it weekly exercise. I’m leaning towards this as being the solution. I still have more research to do on it.

  4. David Lloyd Sutton says:

    Walter, I called an old electrical engineer friend (he’s the guy who did the telmetry for the Thematic Mapper satellite) who I know from my time with Hughes. He says your primary consideration is the amperage you have available on site, assuming you have 220 in the first place. Reduction in power to shift to three phase is severe, he guesstimated about 50%, though he was careful to say he’d never actually done such a conversion for anything as big as your convertible. Suggested, however, that you look into acquiring a PTO-run three phase generator to keep on site. Said a neighboring dairy used to use that method. If you are dehairing just an hour or two a week, idling your tractor (rpm setting has to be pretty steady for steady oscillation) to run a generator that costs a couple of thou can’t be as prohibitive as $50 K to bring in commercial three phase!! He suggested that for a worse-case scenario you price such a generator with an outfit named Grainger, as they have the highest prices of anyone. Good luck.

    Lighter note. My little western, Big Hills, is out on Amazon as of two days ago!! Frabjous.

    • Cool, David! Congratulations. And it’s in Kindle too. I will be interested to know how that does. The wave of the future. I have many, many, many paper books and mixed feelings on reading them digitally as well as all the issues that are going on with digital book compatibility and other things. I like your quote: “I was a bloodthirsty child” he says. Hope would approve. She’s going as the bride of Frankenstein for Halloween and has already picked her flowers so they’ll be nice and wilted by the big night.

      The president of our electric company also suggested a PTO generator as one of the things to look into. There are several other pieces of equipment like the grinder and the vacuum sealer that may benefit from three phase power. All of them are only used for a little while, none use as much power as the dehairer and all would only operate when the others are off. I have my research time cut out for me…

      Here is a link to David’s book Big Hills for those who want to go see it on Amazon.

  5. Valerie says:

    I just read in this week’s Seven Days that Pete Johnson thinks the fire that burned down his barn was started by a phase converter. It was at the very end of the article. (Sorry no link, was reading the paper version.) The article was about Pete’s Greens and their new barn. You might ask him (or someone on his farm) for some opinions.

    • Very interesting. I will look for the paper and try and contact him. Wait, I might have found it. Was it back in March that you saw this article or is this a new article you saw?

      In Pete’s case he had a wooden building. We’re building with concrete everywhere with massive fire breaks to stop this sort of problem.

      I would be interested in talking with him.

      • Valerie says:

        Nope, it was just this week. http://www.7dvt.com/2011inch-inch-loan-loan-petes-greens-makes-its-garden-grow-back

        “Although fire investigators never determined the cause of the blaze, Johnson suspects it was a three-phase power converter used to run an industrial-size salad spinner. The new barn is wired for three-phase power, which is used to run larger electric motors, but the old barn wasn’t and required a converter. Johnson says he found the converter blown to pieces in the barn rubble, while items beside it were merely charred. ”

        It sounds like you’re pretty safe from fires, but I bet it would still ruin your day if your phase converter exploded…

        • Valerie, thanks for that link. Yeah, a blown up converter would be a bummer. Especially since it would be in the same room as our refrigeration compressor. Hmm… I’m thinking about this. David’s suggest has given me an idea that I’m exploring. A dedicated backup 240VAC 3-Phase generator which we turn on during processing. It skips the whole need for the three phase converter. I was going to get a generator anyways so this might be the best solution. The weekly runtime for slaughter day will also exercise the generator – something it needs.

  6. mellifera says:

    Here’s the word from The Nuke Engineer. It’s mostly Greek to me so I’ll just C&P.

    “There are two varieties of phase converter: Mechanical (or “inductive” or “rotary”) and static. The Mechanical ones are simply three phase motors that are hooked up to only one phase of power, started up (usually by means of a small “pony motor” or a pull-starter), and then three phases are pulled off of it. These are about as simple as you can get, and they work just fine, particularly if you are turning other motors. If he wants to go cheap, he can find a used 3 phase motor somewhere, hook up the wiring himself, and he’s in business. What he needs to do is get a motor with 3 times the horsepower rating that he needs to run, and make sure that his rural single phase service can provide the Hp.

    The solid state varieties are essentially big rectifiers that take the single phase, convert it to DC, and then invert it into three synthetic sine-wave phases. They vary in sophistication and elaboration… as well as price. These are really flexible because they can easily be adapted for variable speed drives and are widely used in industry when it is desirable to dynamically control the speed of things like production line components. But if you are simply converting single phase to three phase for fixed speed motors, then the rotary type is the most economical and practical.

    I am not personally familiar with actually doing any of these installations, though I did look into it many years ago because it is frequently easier to locate and cheaper to purchase 3-phase equipment than single-phase industrial equipment. If you want a good quality industrial grade table saw or band saw, 3 phase is about the only way to go.

    Here’s the fundamental questions:

    1) What is the available voltage and amperage of his single-phase service?
    2) How much power does he want to run? Include *all* equipment that will be running at once (Hp ratings), lighting (in Watts or KW), any refrigeration loads, etc… a good way to do this is just go to the breaker box(es) and list all the breakers, their ratings, and what are really on the circuits (i.e. typical residential lighting circuits are 15 amps at 110 VAC, but will only have ~200-400 watts drawing only 2-4 amps).

    With these two bits of pieces, it will be a simple matter to determine if he has enough power available to run the loads he wants. After that, sizing the phase converter is pretty simple. Send along my e-mail to the gentleman if you would like, and if he can give me the info above, I can give him some suggestions on whether he’ll be able to power it, and perhaps point him to some plans for making the converter himself.”

    I’ll forward his email to you as well, so you can contact him if that would help.

    • Thank your father for his words of wisdom.

      1) Incoming power is:
      240VAC
      1-Phase
      200Amp

      2) Power consumption
      Dehairer is 17.2KW:
      15KW resistive load for heater
      2.2KW resistive load for motor

      During the time the dehairer is in use there are no other significant loads.
      Refrigeration could be turned off during dehairing.
      Lighting is minimal power consumption.
      A few minor computer equipment functions that are minimal.
      Everything else could be turned off.
      Thus besides dehairer I would put everything else together at less than 10Amps 120VAC or 1.2KW.

      If it were not for the one year warrantee on the dehairer I would take it apart and run a separate power cord for the resistive load that heats the water tank for the scalder leaving just the 2.2KW inductive load of the motor. I have a copy of the wiring diagram (in German) and that looks quite feasible. Basically a wiring harness adjustment. But, there is the warrantee and this is $40,000 machine so I hesitate to hack my brand new convertible while it is still under warrantee. :)

      The rotary phase converter is my next option. I come up with it needing about a 40HP unit. Does that look right? My math is here:
      http://flashweb.com/blog/2011/08/three-phase-power.html#comment-39150
      and I would love to have someone go over it and check it for me. Two big questions I have are about efficiencies during usage and during idle.

      David gave me a third idea I wonder about. He suggested a PTO generator of the tractor. I can’t tie up the tractor or wear it like that so that idea was close. I am intending to get a standby generator anyways because we must have power for the refrigeration during the critical 18 hours of temperature pull down immediately after slaughter each week when the carcasses are cooled from 103°F to 40°F. If we lost power for four hours during that time we could lose our week’s product. This raises the idea that rather than messing with a rotary phase converter I simply turn the generator on each week (runs off of propane, diesel?) and power the dehairer with the generator for the five hours of run time we need and then turn off the generator. This gives the generator a weekly workout which is good for it. It also saves me from having one more piece of equipment (rotary phase converter). Generators and rotary phase converters are about the same cost so it also saves me a large equipment cost. It would run for about five hours a week at about 50% load. I would be very interested in knowing your father’s thoughts on that idea. I have no experience with backup generators, yet.

      All thoughts and feedback are greatly appreciated! Tell your father the moose was watching the tame life carrying their boxes around the mountains – They hide behind the trees so you won’t be scared off.

  7. Marc says:

    Hi Walter,

    re your above maths –
    you say the machine has an “Einspeisung” of 400V originally?
    that would make the power consumption as follows:
    15kw / 400V = 37.5Amps
    2.2kw / 400V = 5.5 Amps
    Total: 43Amps
    maybe that explains why they run it of a 60amps plug?
    Germans would never run a 62.5Amps load through a 60amps plug – knowing coz I’m one myself! ;-)
    Let me know if you need any help with translating the doc.

    Appreciate your blog – 3 weaners on pre-order!
    Thanks,
    Marc

    • Ah-ha. Yes. Thanks. 400V instead of 240V for the division. 43Amps fits with what the salesman said which is that the unit actually uses closer to 35 or 40 Amps in actual use. I thought something must be wrong since I was coming up above the Amp rating of the breaker.

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