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3 Phase Converter Schematic. (Miller system)

Discussion in 'RE Projects' started by tcmtech, Nov 27, 2009.

  1. april

    april Member

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    You Know if Old Les concentrated less on selling his plans or motor or whatever he is trying to sell via this thread, the discussion might be more constructive.

    My result was 46uF and 10 uF with 460uF as start cap .

    I have found I can reduce the start cap when the motor is not loaded but I have left it there to ensure no damage when I put it on the load.
    I also wondered what will happen to voltages on each line if I reduce the 46uF and increase the 10uF - whether they will still balance out or whether it will throw the whole lot out. When I get back to putting a load on this I will test that too.

    As a capacitor in the line changes the phase angle by 90 degrees only and the phases in 3 phase motors are normally 120 degrees apart , I must admit I am at a loss to understand why this works at all. However work it does.
    I suppose that 90 degrees is 3/4 's of 120 so its close enough

    Obviously each motor is different and each winding is a different resistance so the tank circuit created is different for each.
    I might experiment also with swapping the same value caps to the opposite lines and see what happens.
    The video posted by that guy in New Zealand on my thread shows him switching to delta from star while the motor is running and the voltages on each phase jumping to 500V so I am intrigued what will happen if I do the same with my motor
     
    Last edited: Apr 28, 2013
  2. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Well I made this thread just so that people could get the schematics for a good and adaptable phase converter design for free and so that those who are selling designs would get less sales. :p

    As far as the rest of your questions go the first few posts cover most them.
     
  3. april

    april Member

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    No they wern't questions just musings .,deliberations . Merely wondering why
     
  4. dave

    Dave New Member

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  5. OldLes

    OldLes New Member

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    April, in my last message, I contrasted the significant C1:C2 ratio that TCM's original circuit predicts with those I found. If you look at those values, and those you yourself have just listed, you will see the same anomaly, but then TCM does advice "tuning" your own setup for optimum.

    I suppose it is worthwhile making the point here that not only are we comparing apples and oranges (Star and delta connections) but we are also bringing in bananas (RPCs as well as statics)

    April, sorry if my blatant advertising upsets you.
    Maybe you would find something more in what I have written here if you put that part out of your mind and study the content.
    About 5 years ago I spent some time optimising a 230v to 230v delta connected RPC, which I freely placed in the public domain. Last year however, I spent some months of my time developing my current working system providing a 230v single to 415v three phase WITHOUT the need for a transformer. It took me so much time because I met so many unforeseen problems, which had me ready to abandon the project and spend money on a commercial unit a few times. However, being a bloody minded and persistent "so and so", I neglected my Cagiva Alazzurra and kept at it. It took so much of my time that I thought I was justified in attempting to get some financial "payback". I have yet to have any dissatisfaction expressed by my customers, for whom I provide ongoing advice with a view to further improvements.
     
  6. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    In the US based power systems most three phase motors use two sets of Wye windings and either use them in parallel for the lower input voltage or stack the second set on the ends of the first set for the higher input voltage.

    Because of this it's easy to make a 240 volt single phase input to 480 volt three phase output converter without any extra parts.

    All that is needed is to tie into the mid points of the phases on the 480 volt configuration to feed the 240 VAC to the unit while using the 480 VAC end leads as the higher voltage output making what is basically a 240:480 step up rotary autotransformer.

    I wasn't aware there was much of a demand for such converters but I think that now justifies me adding some new schematics to this thread or perhaps just making a whole new second thread dedicated to other RPC designs! :D
     
  7. OldLes

    OldLes New Member

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    Interesting. I was aware that there were differences (other than simply voltage), but was unaware of the complexity.
    Here in the UK, most motors are now supplied as six terminal ones for use with 230v (delta connecte0 or 415v (star connected).
    Most older motors were supplied as three terminal, 415v star connected types. Some (generally higher power) motors were three terminal star connected. Occasionally there were six terminal motors (again usually higher powered ones) which could be used in star / delta run / start mode, for example on large fans.
    I have a six terminal 2HP motor which is a two speed motor as used on a Colchester lathe.
    Les.
     
  8. Rotarymaker

    Rotarymaker New Member

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    Very interesting indeed ..... cannot wait for your upcoming posts on this Tcmtech!
    A little while back I joined this great site and started a new thread requesting info on an old (UK 230V) commercially built 15HP 230V to 415V converter. ..... a RM Trident 15. I got no replies, but a lot of people were interested enough to read it.
    At present, I have it all stripped down and am in the process of reverse engineering it's circuitry (for future fault-finding of course, as there isn't an ounce of info out there on it!..... and the original company, as far as I know, is no longer in exsistance and therefore unable to supply me with support.)
    It has a massive toroidal step up auto transformer inside which produces 415V from the 230V input and a 9 bank of 50uF 450Vac oil filled capacitors, all switched in as necessary (I guess, according to startup / load conditions, via seven 4 pole heavy contactors)
    There is a pcb circuit board controlling these contactors via seven smaller relays, driven with approx 15 very common CMOS logic and Linear integrated circuits, from which I intend to trace out the schematic, with my future intention of perhaps modifying the circuitry to total modern solid state operation. (SCR / IGBT/MOSFET switching.
    I thought that OldLes would have read my old post and would have chirped in by now, but his info / knowledge is hard to prise out and seems to be top secret.
    Sharing and discussing has always been my way of thinking, so no matter what time I spend, I'll let all know how my project goes.
    ..... hopefully it may be of some help to Rotary DIYers and complement Tcmtech's up and coming converter schematics.
    anyone interested???
    cheers,
    Rotarymaker
     
  9. OldLes

    OldLes New Member

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    It seems to be "moan about OldLes" week, maybe I should simply withdraw from this forum? Your choice!
    Rotarymaker. I have not seen any message from you, so am in no position to comment one way or the other, so don't complain I have not helped you!!!!!
    Unless of course, you have changed your identity, and transformed a Trident 30 into a Trident 15??
    When GEDW asked about his Trident 30, I replied to the best of my knowledge.
    I joined this forum in March last year. At that time my knowledge of RPCs was limited to a 230v delta unit I created a few years before. My interest was re-kindled when I saw a crude Utube experiment which produced a 415v supply from a 230v input without transformer. I decided to look into this as a way to drive my new (but old) lathe, and it was about September when I finally completed it. Whether or not members here approve, I made the decision to try to recoup something following four months of patient development. As to "being secretive", I have given many people help, here and elsewhere, but knowing how long it took me to develop this (and consider I am a septuagenarian with experience in many fields but excluding industrial electricity. I don't think simple "how to"s would be much use to most people. I have produced 10 heavily condensed A4 pages, and I urge its recipients to read it many times before commencing a build or asking questions (to which I readily reply). Nobody has yet complained of being "short changed", other than people HERE whose only input seems to be easily accomplished computer keystrokes. Just give the word and I will exit the forum, which I may decide to do in a day or so in any event. OldLes.
     
  10. Rotarymaker

    Rotarymaker New Member

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    Aghh come on OldLes,

    Nobody is asking for your resignation from this site, can you not accept just a little ribbing for your sales pitch of your rotary converter?
    If not, then please accept my apology for offending you......sorry.
    I know you've helped others, please don't take it all to heart, ...... please stay, I totally welcome your input / criticism and advice on my up and coming hacked and modded 15hp rotary converter.

    now eating humble pie, :eek: :eek:
    Rotarymaker

    PS. When you do get a spare moment, please do have a look at my old unanswered Feb 20th thread named RM Trident 15 (15hp?) .... your comments are most welcome.
     
  11. OldLes

    OldLes New Member

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    Rotarymaker, apology accepted. I joined this forum after a google link to this (TCM's) thread, and have not explored any other threads. Will you give a link to your message, then I (and maybe others) will follow it.
    OldLes.
     
  12. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    I will see about working up a bit more info while I can.

    Given that this thread is somewhere past 36,500 views I suspect that more than just a few people have been putting the designs here to work so that's motivation enough for me to work on some new additions while I have free time this summer. :D

    As far as who can make money off of anything they can find here I don't mind and could care less.
    Same goes with other providing additional info. If it relevant and could be useful to people in other locations other than where I am from I don't mind seeing it one bit. :p

    As far as my design goes its well proven and to be honest the very first version of it was created by me back when I got into college just out of high school somewhere near 20 years ago now.
    I had a electric motors theory and lab class where someone asked the instructor if three phase motors could be ran on single phase. He said yes but wouldn't give any details other than it's not efficient or practical.
    From there I set out to prove him and the general consensus wrong! :p
     
  13. Rotarymaker

    Rotarymaker New Member

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    No probs OldLes,

    Here's the link as requested.....a bit of a long one!

    Code (text):
    http://www.electro-tech-online.com/threads/rmk-trident-15-15hp-rotary-3-phase-converter-info-required.133035/
    I must get a few photos up onsite to perhaps raise your/others interest levels.

    appreciate your acceptance of my apology .... glad you're sticking around.

    cheers,
    Rotarymaker.
     
  14. OldLes

    OldLes New Member

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    Attn GEDW

    GEDW, if you are still visiting this thread.
    I have just responded to Rotarymaker in his own thread, where he reproduced my original reply to you on July 7th last year. At the top of the message, it seems to imply that you contacted me through Skype. Maybe I am misunderstanding that, but I can say that I do not recall ever having a Skype conversation with you, and you don't appear in my contacts list.
    How are you progressing with your project?
    OldLes.
     
  15. Rotarymaker

    Rotarymaker New Member

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    Hi all,

    To save confusion and constant forward and backward searching, and not to try and take anything away from Tcmtech's info, I've moved / continued my thread on my Trident 15 Rotary Converter project, to my first request info page here....

    Code (text):
     http://www.electro-tech-online.com/threads/rmk-trident-15-15hp-rotary-3-phase-converter-info-required.133035/
    hope you all don't mind,
    Rotarymaker
     
  16. OldLes

    OldLes New Member

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    Getting back to "conventional" phase converters (in this case static not rotary), a pal of mine had the remnants of a Westinghouse single to three phase converter. All I got to see was the remains of the box it came in, but there were instructions and general info stuck inside it. I took some rather poor photos, and later tidied them up a bit, without any colour. Down at the bottom, a little printer's style mark suggested that they were printed in Nov. 1945.
    The other point of interest was that they were rated for a maximum continuous out put of 4kVA for a 400/440v input supply, but only 3kVA when supplied by a 200/250v supply.
    In other words, they were DUAL VOLTAGE supply. I suppose any (edit. NO! Most) inverter incorporating an auto transformer could be dual voltage, just like my 230/415v Citringham welder!
    I think the Westinghouse would take a bit of "driving", as there are many adjustments (alternative connections) to make.
    To give you a flavour, I am attaching a couple of JPGs. I must confess I have never sat down and tried to put all the JPG parts together to "reverse engineer" exactly what it is/does.
    OldLes.
     
  17. OldLes

    OldLes New Member

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    I will try again with the attachments.
    OldLes
     

    Attached Files:

  18. mk1wideboy

    mk1wideboy New Member

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    Hi all.

    After many months contemplating it, I finally got around to building an RPC (a very basic one I may add). I didn’t want to spend a lot of money until I was sure it was going to do the job I need it to do. All I’ve had to buy so far is the motor (230/400v, 7.5kw).

    I’m based in the UK.

    The item I wanted it to power is a three phase roller brake tester. The only parts that need 3 phase are the x2 pit rollers (415v star, 3kw each), all the rest works at 240v single phase.

    The issue I’m having is the large volt drop when I switch the rollers on. See below:

    No load:

    · 9.7 amps on incoming 240v single phase supply
    · L1-L2 401 volts
    · L2-L3 401 volts
    · L1-L3 390 volts

    1 roller motor running:

    · 24 amps on incoming 240v single phase supply
    · L1-L2 375 volts
    · L2-L3 361 volts
    · L1-L3 373 volts

    2 roller motors running:

    · 34 amps on incoming 240v single phase supply
    · L1-L2 360 volts
    · L2-L3 336 volts
    · L1-L3 360 volts


    Although the item works, I’m not happy with the large volt drop, and it can’t be good for the motors. On some occasions the RPC motor stalls when I switch the 2nd roller motor on.

    The system I am using doesn’t use a transformer to step the voltage up. Instead I’m using a duel voltage motor 230/400v set-up, with a capacitor between L2 and L3. I also don’t have a start capacitor. I just spin it up with a drill, then switch it on.

    Can anyone suggest any solutions? Would I have more success with the transformer set-up? Or is this the best I can expect trying to get 415v 3 phase out of 240v single phase with an RPC?
     
  19. OldLes

    OldLes New Member

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    Rpc

    If your incoming power supply is "hard enough", and your slave motor big enough, then your capacitors are probably too small.
    Your motor is clearly marked 230/400v is it?
    Les
    p.s., Really this is not a "Miller system", so probably should not be here.
     
    Last edited: Jun 17, 2013
  20. mk1wideboy

    mk1wideboy New Member

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    Didn't know where to post it. Had read through this thread and their seemed alot of interest.

    The incoming supply is good and the slave motor should be big enough, at least for only 1 motor running.

    Yes the motor is marked 230/400v, has 6 terminals and a diagram showing how to connect in star or delta.

    When you say the capacitors are to small, do you mean in capacitance or voltage rating?
     
  21. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Sounds like you don't have anywhere near enough capacitance and the converter is not running with a balanced phase setup either.

    The formulas I have given in this thread should get your phase balancing close enough to keep your phase to phase voltages within the normal working ranges of all of the motors when powered up.

    For a rough guess assuming you are using the standard 220 -240 VAC 50 Hz power source the two run capacitors should be around 80 - 120 uf for the main converter motor and around 30 -50 uf for each driven motor.

    It may not be exactly correct but anything in these ranges should get your voltages much closer to where they should be.
     

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