Free 186 More Best Homemade Tools eBook:  
Get 2,000+ tool plans, full site access, and more.

User Tag List

Page 16 of 23 FirstFirst 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 LastLast
Results 151 to 160 of 227

Thread: Rotary Phase Converter (Create 3-phase power from a single phase source)

  1. #151
    Supporting Member
    Join Date
    Oct 2016
    Posts
    1,113
    Thanks
    25
    Thanked 345 Times in 242 Posts

    old kodger's Tools
    Junker2
    I'll take your points one at a time (as far as possible)
    (1) I have contacted the manufacturers of the welder, AND IT IS THEY who said that the machine is simply three individual transformers of 240 volts, and that they
    use 3 phase supply to reduce cabling and contactor sizes
    (2) It happens that I DO know what a power factor is And in this instant, it's value. I simply forgot to include it in my post (.8)
    (3) If it pleases you to attempt to intimidate me, then I bow to junker2, God of electricity.

    186 More Best Homemade Tools eBook

  2. #152

    Join Date
    Feb 2017
    Posts
    23
    Thanks
    0
    Thanked 0 Times in 0 Posts
    If you can wire the welder in a 240 volt three phase delta configuration you should have an economically feasible solution to build an RPC using a 240 volt delta motor as the idler. That is what your original complaint was about right? This does not require the unnecessary expense of a transformer. If it were me building it, I would use a bank of start capacitors and drop out relay instead of a "pony" motor for starting the idler. Reason being no extraneous moving parts, no belts/pulleys, and no fabrication expense for mounting it.

    2000 Tool Plans

  3. #153

    Join Date
    Feb 2017
    Posts
    23
    Thanks
    0
    Thanked 0 Times in 0 Posts
    i thought u quit nhengineer
    did u study engineering or business at that eastern college?
    cause all u want to do is sell me your inferior plans. I might review your plans for a nominal fee. coming from a REAL engineer
    It seems you do not want to discuss any of the technical problems
    Gee , i wonder why?
    Last edited by Junker2; Mar 18, 2017 at 01:18 AM.

  4. #154

    Join Date
    Feb 2017
    Posts
    23
    Thanks
    0
    Thanked 0 Times in 0 Posts
    nhengineer is not a REAL engineer

  5. #155

    Join Date
    Feb 2017
    Posts
    23
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Apparently he is a dumb ass
    Last edited by Junker2; Mar 18, 2017 at 07:55 AM.

  6. #156
    Supporting Member
    Join Date
    Feb 2016
    Posts
    122
    Thanks
    22
    Thanked 21 Times in 19 Posts
    Junker2
    I fully agree any one bragging about there titles are just wanna be's or maybe he needs the money

  7. #157
    Supporting Member Paul Alciatore's Avatar
    Join Date
    Mar 2014
    Location
    Beaumont, TX
    Posts
    303
    Thanks
    9
    Thanked 155 Times in 82 Posts

    Paul Alciatore's Tools
    This is quite true, but, as has been pounded into me several times, transformers, at least at this power level, are apparently very expensive in Australia.

    AND, this is a discussion about converting 240V, SINGLE phase power to run a three phase motor, not using TWO 240V phases/lines for that purpose. If, as was shown above, you connect a single, SINGLE PHASE line to two of the phase inputs (A-B and B-C for example) of a three phase motor, you will either have a short circuit (you would never actually do this) or ZERO Volts across the combination (A-C), not 480 Volts. In either case, the three phase motor will not run, even if you start it with a pony motor or rope. This is clearly not a possibility.

    Since Australian single phase power is 240 Volts, I would think that their three phase power MAY be three of those single phase lines or three, 240 Volt lines that are 120 degrees out of phase with each other. If that is the case, then wouldn't the most popular Voltage for a relatively small three phase motor there be 240V, three phase? With zero experience in Australia, I may have that wrong so any Australians please feel free to correct me on it. But if that is true, then Y connected, three phase motors found there would be expecting no more than about 416 Volts across any two terminals. And I would think that delta connected ones would also expect about 416 Volts. In either case a single, 240 Volt phase could safely be connected to any of them. if it does not run, I would remove power after a few seconds to prevent heat build-up, but other wise it will be safe; no insulation breakdown, no arcing. In fact, the hard part may be finding a three phase motor that will run on a lower Voltage, not a higher Voltage one.

    Also, I may not completely agree with everything that nhengineer has said, but I do not think it is helpful to use personal attacks. I don't recall exactly what he may have said his educational background was, but a degree is not everything. Experience is a big factor, probably a more important one. In my case, I do have a degree, but not an engineering one. It is in physics, which includes electricity and magnetism. So I do understand E-M at a very fundamental level. And I also have a career of experience in TV engineering which may be oriented towards electronics, but many of my employers expected me to design, install, and fix almost anything that was the least bit technical in the building or around it. I once had to solve a problem with rain water getting into the boss's office. Repaired door openers. Did roof work. I even had to fix toilets in some places. And perhaps more pertinent, HVAC work was present in every job I ever had; sometimes only on an emergency basis, but always there. Ever try to get an AC technician up a mountain on a Sunday? Heck, you couldn't even get them on the phone.

    One thing that my experience has taught me is that I CAN be wrong. And I try to watch for it all the time.

    Anyway, give the guy a break. Do give your arguments here, but also listen to his and to others. And think about them before answering.

    I can't resist another comment on that transformer expense thing. Someone above said that it would be better to buy a motor-generator instead of using a transformer. Is this really the case? How, at the SAME power level, can a motor-generator cost less than a transformer? In the motor-generator, BOTH the motor and the generator would have to have at least as much and probably more copper and other metals than a transformer with the same power rating would have. And there are moving parts that require things like bearings. There are more parts in the motor-generator and it's assembly is more involved. That easily adds up to more than twice the metal and therefore should be more than twice the cost of the transformer. Doesn't it? Is there a special tax on transformers in Australia? Or was that poster ill informed? Or is this the business opportunity of the century for an Australian entrepreneur to make or import transformers?



    Quote Originally Posted by old kodger View Post
    nhengineer,
    I couldn't help myself!

    Junker2,
    It might be a good idea for you to go back and read all the previous posts. this particular part of the discussion is referring to AUSTRALIA, stop thinking America. We have a minimum of 240volt motors, and three phase motors are ALL 415volt (read Paul's post about vector maths) two 240 volt phases 120 degrees out of phase will produce 415 across L1 and L2, jeesh!

    Rob.
    Last edited by Paul Alciatore; Mar 18, 2017 at 03:03 PM.
    Paul A.

  8. #158
    Supporting Member
    Join Date
    Oct 2016
    Posts
    1,113
    Thanks
    25
    Thanked 345 Times in 242 Posts

    old kodger's Tools
    Paul A.

    It was I who made those comments, and I will agree, without verification.
    So, without emotion, here are the answers to your queries. I did this research only two or three days ago. a transformer to give 480 volts center tapped and capable of 8kva,(I asked for a ball park figure) was at least, and upward of $1650.
    Some three months ago I bought a second hand, 5kva unity pf diesel generator for $450. now I'll be the first to agree that these two things are not quite the same, but upping the generator output to 8kva is not so big a jump, so whilst I cannot give you hard and fast costs (they are after all second hand), you can see why I might have made those comments.

    Rob.

  9. #159
    Supporting Member
    Join Date
    Oct 2016
    Posts
    1,113
    Thanks
    25
    Thanked 345 Times in 242 Posts

    old kodger's Tools
    Paul,

    Oh, by the way, I'd have to buy the idler motor as well. Checked that one out as well, nobody wants to give one away, if it works,they want to sell it as a going concern.

    Rob.

  10. #160
    Supporting Member smithdoor's Avatar
    Join Date
    Feb 2016
    Location
    Clovis CA
    Posts
    59
    Thanks
    0
    Thanked 16 Times in 9 Posts
    I know the way the draw shows is simple use sign phase motor to turn a three phase motor after up to speed give power the main motor and disconnect the sign phase motor.
    I do not know if he ever had any engineering ???. He does not sound like a engineer.

    Dave

    Quote Originally Posted by Junker2 View Post
    nhengineer is not a REAL engineer

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •