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  1. #1
    Join Date
    Oct 2007
    Location
    Sydney
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    3,112

    Default Hercus 3 phase lathe, single phase supply

    G'day Guys, I FINALLY got my lathe, an ex high school Hercus. I don't have 3 phase to my property, and after investigation found it too expensive to consider. So with the lathe I could either put a single phase motor on it or I believe I can get a VFD off ebay and use that.

    I have plenty of experience with electrons but absolutely zero with VFD. Is there any tips or advice available on using a VFD as a single to 3 phase converter on a lathe like this? I'm also wondering about the ability to reverse the lathe as it's imperial and any thread cutting I'd do would be metric.

    Thanks,
    Pete

  2. #2
    Join Date
    Feb 2007
    Location
    Katherine ,Northern Territory
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    69
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    736

    Default

    I am in the same situation at my place ,as far as 3 phase goes. I have been looking at a rotary 3 phase converter. It would be better to keep the lathe 3 phase from what I under stand they are smoother running with less vibration than a single phase ,some thing to do with phase balance or some thing.
    I don't think a VFD is is the right device.
    I have done some reading online regarding rotary phase converters and they are also commercially available .Not being a sparky ,I haven't really fully understood the concept.
    I'm not into electrickety so I might be spouting BS here
    What I have gathered is you feed 240 volt power into the 3 phase motor and use a single phase motor to get it spinning and the 3 phase motor out puts 3 phase.

    There are discussions and instructions online to build them and how they work , some wiring diagrams as well.
    Some one on this forum has also built one if I recall correctly .
    Just do a Google for phase converter.

    Kev.
    "Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
    Groucho Marx

  3. #3
    Join Date
    Jun 2007
    Location
    sydney ( st marys )
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    64
    Posts
    4,887

    Default

    Not knowing the cost of phase convertors or VFD's why not just go with the single phase motor and reverseing drum switch.

    In regards to the mention of vibration of 3 phase / single phase wouldn't have a clue either.

    In my opinion I would go for the cheapest allternative,but would try to have at least 1HP.

  4. #4
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    As I understand it, the VFD converts either single or 3 phase input (depending on the model) to DC then back to 3 phase AC with variable frequency to control the speed. So I can't see any reason why not to use a VFD for 3 phase power.

    I'm uncertain about whether the motor fitted will be suitable however. It looks to be the original, branded GMF. I have no clue about star and delta windings but the 3 wires from the "guts" of the motor into the terminal box on the motor simply terminate at standoffs, ie there is no possibility to change connections there that I can see.

    As for the motor size, they are remarkably small, the standard motor is 0.5 hp

    Cheers,
    Pete

  5. #5
    Join Date
    Aug 2003
    Location
    Conder, ACT
    Age
    77
    Posts
    2,803

    Default

    If it is only 1/2hp then the cheapest option would be a 3/4 hp single phase motor with reverse.

    (3 phase has more torque than single phase so you need a bit bigger motor)

    Other options are as given above and the old faithful, a seperate 3 phase generator which is always useful.

  6. #6
    Join Date
    Jan 2007
    Location
    Katoomba NSW
    Posts
    209

    Default

    Not all motors are suitable to use with a single to 3 phase VFD conversion.
    In this case the cost of either a VFD or a rotary phase converter would be significantly more than a 3/4 or 1 HP single phase motor.
    If possible find a motor that has the same size shaft as the old motor so you can reuse the pulley.
    Built: a Bench,a Desk,an Archery Display,

    Those were the droids I was looking for.

  7. #7
    Join Date
    Jun 2008
    Location
    Lindenow
    Age
    50
    Posts
    869

    Default

    Hi there,Phase changers are the way to go.As mentioned above the best choice is a rotary phase converter.These range in price according to the size you buy. I have just bought one and the costwas $4800 this includes having a sparky come and wire it in.My pase converter will run my lathe and mill as well as my 350 amp welder.the best place to go is phase change converters australia they have a good website with all you will need to get started.I hope this helps you a little
    Warning Disclaimer

  8. #8
    Join Date
    Jul 2008
    Location
    Beveridge Vic
    Posts
    5

    Default go for the single phase

    G'day all
    Agreed the Phase Changer rotary converter is good, and gives approx 415 volts per phase, so standard 3 phase motors can be used. As I understand it, VFDs put out 240v per phase, so the motor needs to be 415/240. However, unless you will be using several machines with 3 ph motors the price of the converter probably is a bit much. I would go with the single phase, my old Model A has a half horsepower and will slip the belts before the motor is distressed. The belts flapping around and runout on the pulleys will give far more vibration than the single phase motor.

    Evan

  9. #9
    Join Date
    Jul 2003
    Location
    The Fabulous Gold-plated Coast.
    Age
    69
    Posts
    2,251

    Default

    I have a homemade 7.5kw rotary phase converter...less than $500 to make yourself which is of course illegal here or something. Plenty of plans and info online.

    Three phase power on a lathe or any machine tool is a good thing. You do get better surface finishes because the torque is more evenly produced as the shaft rotates...kind of like a three cylinder radial engine compared to a one cylinder engine, if you pardon the crude analogy.

    VFDs seem to me to be the best way, hands down, of converting single phase to three. The current biggest three phase that you can power with an easily purchased VFD is 3 hp, although Polyspede in the US have 5 hp and greater models.

    Phase converting VFDs come in 240v single phase input. This you need a 240v three phase motor. (A motor that is 415volt star connected can be configured 240 volts via the delta windings. The biggest motor that you are likely to find in Australia connected 415 star is maybe 5 hp or so. (Not a factor for you).

    Since the modern VFDs can drive a motor at very slow speeds some alternate cooling method for the motor must be provided...the shaft driven fan obviously does not do an adequate job at low speeds. Hence the point that not all motors can be used with a VFD. They can't, but fitting a separate fan takes care of that.

    VFDs also allow you to select speeds via a potentiometer which can be mounted in a convenient place. Reversing can be done using any old low voltage switch wired through the vfd's control terminals. They also have provisions for variable stopping time on the spindle...a nice thing to have with a screw-on chuck.

    I am in the process of restoring a toolroom lathe and I have to use a VFD for reasons unrelated to this topic. So far the best prices are ex-USA (even shipped) I find it difficult and stupidly, wildly expensive to find a 240v VFD here.

    Some brands that I would consider are: Teco (Westinghouse) Ac Tech (Lenze) and Hitachi. Sometimes eBay will yield a Danfoss, Allen Bradley or Sew Eurodrive. SEW make very good units.

    It won't be a factor for you, but other readers should note that when powering higher power motors you need an over sized circuit because the inrush current is higher than nameplate current owing to capacitor charging requirements internal to the VFD. Those same capacitors dislike sitting on a shelf for years. If you purchase an old unused VFD it pays to Google "reshaping capacitors". Generally giving power to the unit for 12 hours or so without running the motor will do it.

    Good luck with your decision!

    Greg
    Last edited by Greg Q; 23rd Jul 2008 at 12:19 AM. Reason: to remove innapropriate apostrophe from plural nouns

  10. #10
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    G'day Greg, I took a chance and purchased a SEW single to 3 phase VFD. The specs suggest matching VFD to motor size so this 0.5hp one should fit the bill. However I'm just got a bad feeling it won't be that easy

    The motor is the original and have confirmed it is definitely star configured (with no option for delta). The output from the VFD is quoted as 3 x input voltage ie 230V

    I'd definitely like VFD with not only the variable speed part but soft start/reversing etc. I'd much rather do that electronically than starting and stopping a motor at full voltage as I'm sure it must put a strain on not only the motor but also the gear chain etc etc. Bit like taking off from the lights with your foot flat to the floor, sure the car can do it but would you .... hmmm, I take that back, I live in Sydney and the answer is definitely YES from the way some people drive here :P

    Cheers,
    Pete

  11. #11
    Join Date
    Jan 2006
    Location
    Blue Mountains NSW Australia
    Posts
    408

    Default

    Hi Pete.

    Your little motor will be 415v star I suppose.
    I also assume your vfd will output 240v 3~ which means that your .5hp motor will not run in it's current config.
    Don't despair though. You will need to pull the motor apart and dig out the star connection. Solder three separately wires to these three and bring out to the terminal box. You now have the six wires necessary to wire it up as 240v delta 3~

    I built a 4kw phase converter last year for my lathe, saw drill press etc. I wired my .5hp drill press motor as described above, and it works beautifully.

    Here is a link to a thread discussing the build of the unit.
    http://www.woodworkforums.ubeaut.com...ahes+converter
    Please read carefully though, and disregard some information that I posted that was incorrect. It was huge learning process for me, and I had a few teething problems with the technical side that were clarified by another forum member later in the thread.

    I have recently upgraded the final unit as shown in the thread. I now run a 4kw 3~ motor from this unit to my bench saw. I installed another contactor in the unit, and controlled the cappacitance to start it from the starter at the saw. The extra caps only switch in to the curcuit while the saw is running, and the converter runs without these extra caps for my smaller machines. This way, I have balanced power over all three phases for each machine.... within 3% phase to phase.

    Good luck.

  12. #12
    Join Date
    Jan 2006
    Location
    Blue Mountains NSW Australia
    Posts
    408

    Default

    Hi again,

    Below is a quote from Chris on another board. The instructions he gives in this quote is very close to how I went about the brain surgery on my drill press motor.

    Hi Tim,

    I've done this twice too (or once on a dual-wound two-speed machine in
    fact). Firstly, you need to make sure that you have a machine which is
    star connected for 415 V. If your machine is delta connected for 415 V,
    you can't convert it to 240 V operation, but I'm sure that you already
    knew this. Usually the star point is fairly visible once you've removed
    the end bells and rotor. It will normally be inside some glass fibre
    sleeving, tied and varnished to the windings at one end of the stator.
    Get the motor off the machine and into a comfortable, well lit
    location. When you've got plenty of time and are feeling patient,
    carefully cut the cords which tie the windings together and identify
    which length of sleeving has three wires leaving it (two from one end
    of the sleeve and one from the other). This will be the star point.
    Carefully slit the sleeving with a sharp knife and remove it to reveal
    the soldered joint. You may or may not be able to neatly desolder the
    joint. If you can't, cut the lacquered wire as close to the joint as
    you can. Try not to nick the windings with your knife or nippers,
    although if you do it isn't a complete disaster because you can paint
    over the nicks with insulating varnish. Now take some emery paper and
    draw it along the ends of the wires to remove the lacquer. Be very
    careful not to bend the wire, or it may break. I broke a wire doing
    this and only just had enough to solder onto. If it breaks near where
    it enters the windings you'll have to get a rewind, so it's worth
    taking your time here. Now tin some lengths of stranded wire to use as
    your lead-outs. I used 105 C equipment wire from Farnell, but I
    understand that the temperature rating should officially be higher. It
    worked fine for me, though. I'd attach one lead-out to each of the
    three wires at the star point, and take all six wires out of the motor.
    I don't think it's worth trying to create a delta connection internally
    when you can just attach two wires to each of the three terminals in
    the terminal box. I fitted heat-shrink sleeving over my soldered
    joints, tied everything together with thick cotton and painted it with
    a bit of glass fibre resin. You can get proper insulating varnish from
    Farnell if you want. My motor probably isn't quite standards-compliant
    but it has been working fine for six years now. The whole job took me
    about 3 to 4 hours as I remember.

    Good luck!

    Best wishes,

    Chris

  13. #13
    Join Date
    Oct 2006
    Location
    Armidale NSW
    Age
    52
    Posts
    915

    Default

    Hi Pete,
    I also responded in your other thread in the reno forums. I assumed the VFD outputted 3 x 240V (240V phase to neutral) and Fossil is assuming it's 240V 3~ (240V phase to phase). I'm not sure who is right, but I think you will need to check out the VFD specs a bit more closely to determine what they mean by "3 x 240V".

    If my assumption is correct then the motor will work without modification. If Fossil is correct then it will need to be modified as he mentioned.

    As an aside (and as everyone else is mentioning phase converters) - I built a static phase converter for my workshop that cost much less than $100 (I had a lot of the parts). It runs off 240V split phase (480V) and can run my saw (7.5HP) scriber blade (1HP) and dust extraction blower (3HP) all at the same time ... and I didn't need to reconfigure the motors to run 240V 3~.
    Cheers.

    Vernon.
    __________________________________________________
    Bite off more than you can chew and then chew like crazy.

  14. #14
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    Yeah exactly, I think it's quite confusing. As I read it, the VFD outputs 3x230V measured phase to neutral, which as I understand it, bit grey in these areas is just standard 3 phase????

    Here is a link to the operating instructions http://sew-eurodrive.com/download/pdf/1056411x.pdf

    The unit I have ordered is MC 07 A004-2B1-4-00 ie the smallest VFD they do.

    Thanks for your time guys, much appreciate the input.

    Pete

  15. #15
    Join Date
    Sep 2006
    Location
    A.C.T
    Age
    89
    Posts
    190

    Default Hi Pete from Peter

    I fitted a VSpeed controller to a 2 1/2 hp motor on my Woodfast Lathe, great, easy,Adjacent to the Lathe I had a 20 amp circuit 240 volt so it was uncertain what the start run current would be so I measured it at 7.5 amps start and run.
    A single phase normal motor on start gives a short but nasty surge of thirty to forty amps ie a 21/2 hp one. The VS unit has a soft start that enables that frugal current on startup.
    Now in America two things are different single phase is 110 and also 60 cycles, now a single phase motor run on 240 volts 50 cycles can be used on 60 cycles however a 60 cycles motor used here will overheat very quickly.
    Two considerations when buying from the great USA then are current ratings and then cycles.
    Another requirement in Aussie Law is a form of suppressor that is now included in the price here but not always to prevent a trouble locator knocking on your door with an irate neighbor with them to locate the souce of interference on their appliences such as Radios and T.Vs interference is against the law, mine cost me an additional 80 bucks at the time.
    Have fun Peter

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