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Two Phase???!?

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by RandyWilson, Apr 30, 2017.

  1. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    So I got the new mill home and was cleaning it up some. I found the serial number. And the production date of 1960. And 220V as expected. and Ph = 2. Two. Definitely a 2. So I look at the spindle motor. 220V 2P. We ran this at the sellers place off of a static converter, and it came with a 3 hp RPC.

    I'm about to start tracing wires. I know that in 1890 Ph=2 means I screwed today. But two phase was dead LONG before this machine was built. I'm doing the research, but hopefully someone has a clue what this is about. Did Cincinnati really build 2 ph machines in 1960?
     
  2. Ulma Doctor

    Ulma Doctor Infinitely Curious Active Member

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    first question i gotta ask is how many wires come out of the motor?
     
  3. Superburban

    Superburban United States Active Member Active Member

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  4. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    3. Three plus ground on the lead-in cable. Three from the primary cut-off to the main board, of which there are two blacks and a larger red. Three to each motor, appear to be equal size.

    While traditional 2 phase was done with four wires, they did do it with three. The larger center wire tends to support this.
     
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  5. higgite

    higgite General Manger - Proofreading Dept. Active Member

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    Not doubting your word, but some of those old nameplates are hard to read. Are you sure it's 2 phase, not 2 pole? Can you tell what's the rated RPM?

    Tom
     
  6. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    The name plate on the back of the machine id not fully readable. The stampings are very clear, but the printed part is dulled from being painted over. The spindle motor is absolutely clear, both printing and stamping. Then, there are these two stickers inside the electrics box.




    mill-sticker.jpg
     
  7. JimDawson

    JimDawson Global Moderator Staff Member Director

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    It is possible that it was built as a 2 phase machine in the 60's. I understand that 2 phase is still in use today in some parts of Philadelphia and Hartford, Ct.
     
  8. markba633csi

    markba633csi United States Active Member Active Member

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    I'm guessing that running it from 2 phases of a 3 phase static or rotary is possible but won't give you full power from the motor. True 2 phase requires 90 degree sine waves but 3 phase power is 120 degrees per phase. There's type of transformer called Scott which can convert 3 to 2 phase but it's complicated and expensive.
    Theoretically it would be possible to program a VFD to give two phase output at 90 deg, don't know if any units on the market could do this.
    Changing to a 3 phase motor is probably the most practical thing to do.
    MS
     
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  9. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    It is turning out to be a frustrating subject. It totally stumps das Google, to the point that google doesn't even realize it's giving totally useless 3 phase info. And a search of Scott-T transformers in Ebay gives a page of Travis Scott tee shirts. About the only relevant thing that can be found is various forums where people quote that one wiki paragraph back and forth to each other.

    The original plan was to replace the table motor with a single phase that fit better. The current one has been replaced with a large anchor, and got quite warm when ran on the static converter; replacement was factored into the purchase price. That would free me up to run a VFD on the spindle.. Even though it came with a RPC, I consider those to be bad magic. VFD is good magic. But it looks like I will be trying to tune the RPC to the spindle motor, and running the snot out of it until the dilithiums pack it in.

    Just thinking out lou. It seemed to run fine on the static converter. If the RPC doesn't go well, could it be converter to a static easily? Isn't a RPC just a static in front of an idler motor?
     
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  10. markba633csi

    markba633csi United States Active Member Active Member

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    I'm guessing here again but probably the static converter didn't have enough "tuning" or phase shift on one of the outputs which worked just fine in this case. And/or the motor isn't too fussy about the absolute phase angle. Basically a single capacitor is all you would need: static12x.jpeg You would have to experiment to find the right capacitance value- probably in the neighborhood of 100-150 uF at 330 volt AC? Maybe could borrow caps out of motors you own till you zero in...
    Mark S.
    ps maybe the seller would let you take a peek inside his static converter to read the value?
    pps Capacitor run (also called permanent split-cap) motors all work like this; making 2 phase from single.
     
    Last edited: May 1, 2017
  11. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    The seller is a used equipment dealer. He only ran the machine for testing purposes. He did load it up with some deep cuts into steel, but it wasn't a continuous test.

    It's going to be a while before I have time to play with this in earnest. There's still a rusty '23 firetruck sitting where this mill is going.
     
  12. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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  13. markba633csi

    markba633csi United States Active Member Active Member

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    No problemo- TTYL
    MS
     
  14. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Check out page 23 of the Pdf or page 19 of the original scan.

    Daryl
    MN
     

    Attached Files:

  15. YoungTurner

    YoungTurner United States Iron Registered Member

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    A static converter is "part" of a rotary phase converter. The static converter "kicks" the idler motor to turn which then delivers 3 phase power to run loads. I'm not sure your rotary phase converter will work unless it too is wired for two phase power. I'm not an expert on rotary phase converters by any means though.

    It's quite likely that the static converter the machine was running on would only provide a little less than %50 power. since the way a static converter works is to run on two of three legs. But it would run it.

    If it were me I would replace or rewind the motor.

    I can make a few calls to find out if any VFDs will work in your application, I work with all sorts of VFDs every day.
     
  16. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    YoungTurner,
    You are relatively new to HM.
    I sincerely appreciate your attitude! Thank you.
    Great offer. I hope that we can help you out should you have a time of need/desperation!

    Daryl
    MN
     
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  17. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I do sincerely appreciate the comments and offers of help. But it has not yet been determined how this machine is wired. Only that it was originally 2 phase. I just could not believe something built in 1960 would be 2 phase. But I have found enough evidence, including our estranged brother CincinnatiJA and his 2Ph 1B. I talked to the seller and he did admit that the machine came through a broker/auction (I didn't ask) in York, about 70 miles from Philly.

    I just spent three fright-filled hours, just me, myself, and a H-F engine crane, moving this monster off of the trailer and into the barn. I'm whooppppped with a capital P, and ain't going to be looking at the wiring any tonight. I'll post back when I get the motor cover off and see how it's actually wired.
     
  18. YoungTurner

    YoungTurner United States Iron Registered Member

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    Anything I can do to help. I work in industrial automation, so motor control is a part of that. But Phase converters are a big no in most of the applications I work in so I have poor experience there.
    Plus I'm just lounging around the house sick, banished to the couch as not to get our 3 month old sick. So I'm occupying my time and hopefully helping and not giving bad advice.:D
     
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  19. strantor

    strantor United States Active User Active Member

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    If that's the case then someone out there is probably looking for a spare 2ph motor since they're so uncommon. This rare 2ph motor may be worth money.
    It may be easier AND more cost effective to sell this motor on eBay and buy a 3ph motor and VFD (or a single phase motor).
     
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  20. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Of course I couldn't leave it alone last night. What we have is a 4 pole service box (knife switch) with only three fuses installed and three wires. This leads to the main internal cut off switch (rotary style), again with four poles but only three wired. Then it becomes bundles of wires that I wasn't going to trace last night. So I popped the cover off of the motor. It looks like the wiring connections are up inside the control switch; I don't open it last night. I did notice that the windings have wiring bundles coming out at 36 points around the circle. I am by no means an electric motor expert, but it strikes me that this may be enough that the windings could be bundled in either 90 or 120 degree groups. Add to this the plate doesn't say two phase, it says "two-phase connected". I am wondering if this motor is switchable between 2 and 3 phase by regrouping the windings. Any motor gurus have an idea if this is possible?


    I am strongly suspecting this machine has already been converted to 3 phase.
     
  21. markba633csi

    markba633csi United States Active Member Active Member

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    Do you have an ohmmeter with a low ohms range (x1)?
    Mark S.
    ps try to post some more pictures of motor
     
  22. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    No, all I have is automotive meters with a 200 scale. They are inconsistent with sub-1 ohm tests. Pictures tonight.
     
  23. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Pictures will be coming, if needed. I spent the evening re-wiring the borrowed trailer. It seems I always end up re-wiring any trailer I use. As much as people like to attribute it to old Joey Lucas, Dim-Flicker-Off was invented by 3-M with their damn scotch-lock connectors and developed to a fine art by the trailer wiring industry. A new harness from HF, a dozen FAA approved but splice connectors, and a foot of heat-shrink later.


    This has been an interesting adventure. I learned more today about the 1890 politics of Philly, the city topology, and the battles of Edison, Telsa, and Westinghouse, than I really planned on. I *AM* going to have to dig out that old biography of Tesla I picked up off the bargain table a few decades ago but never got around to reading.


    While Peco offers both five wire and three wire 2 phase, the little bit I found suggests they are mutually exclusive. Since the machine was built to handle four incoming lines, and the motor diagram shows L1-L4, I have to assume it was designed for five wire 2 phase (fifth wire being common neutral).

    The 2 phase diagram on the motor, as others around the web, show 8 connections and four leads coming in. This one has 9 and 3. A few of the wires have the original T-* markings. A few are blank, or too faint for my eyes, anyway. And a few have clear markings of type and manufacturer, obviously not matching the OE wires. Conclusion, the motor itself and been reworked.

    The drum switch has a few wires with non-OE crimp eyelets.

    Ringing out the switch, The connections of two leads to L1 and two leads to L3, which the switch reverses. Bundled wires (with non-OE tape) are two to L2, and the final three ganged together. This does not come close to matching the two phase diagrams, but matches the diagrams I find for low voltage Wye 3ph perfectly.

    Conclusion. The machine has been rewired 3 phase, without correcting the labeling.

    If you want pictures, Mark, I'll dig them off the camera. But at this point I'm 95% positive it's wired 3phase.


    Now my next quandry. Is it permissible to run a VFD off of the quasi-three phase of a RPC? That would save me considerable wiring If I could repurpose the lathe's VFD 220V circuit to the RPC and feed the VFD and mill from the RPC.
     
  24. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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  25. markba633csi

    markba633csi United States Active Member Active Member

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    Hi Randy, yes you should be able to run a variable frequency drive from the output of a rotary phase converter. VFDs rectify and filter the incoming AC to make DC then chop it at high frequency to make the 3 phase output. There may be some distortion of the RPC output because of the loading effect of the VFD however. I can't say how that might affect any other motors that may be connected to the RPC. Or, conversely, if switching other motor loads in parallel with the VFD input might endanger the VFDs input protection circuitry. It might be better to play it safe and buy a dedicated VFD for the mill that takes single phase power in.
    Mark S.
     
  26. Apostle10

    Apostle10 Active User Active Member

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    You're not crazy! Two phase was used (and may still be used) in some parts of PA. Feed from Niagara Falls, I believe. I bought a Sheldon Horizontal Mill (ca. 1950's) which also had a 2 Phase motor. By using a capacitor (trial and error to find correct value) and got it to work fine. If you want to pursue this further, drop me an email and I'll see if I can dig up the information for my hookup. I sold my Sheldon about 2 yrs ago but should still have the paperwork around. Good luck, Mike
     
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  27. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Thanks Mark, I'll figure something out. When I wired this barn not that many months ago, I went all overkill via a 60A sub panel with four 220 and four 110 bays. It's full already, and I haven't even ordered the lift, yet.


    Whether I go VFD or keep the RPC depends on mood, weather, lunar positioning, and what I end up doing with the table motor. It is currently a 3 ph... well some sort of poly-phase motor. I will have to replace it with a single phase to go VFD; which may happen since it's health is suspect.


    I wonder if anyone makes a 240V power strip....
     
    Last edited: May 3, 2017
  28. mksj

    mksj Active User H-M Supporter-Premium

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    VFDs can be used with RPCs, but ones needs to factor in the quality of the wave and voltage stability. Most VFDs have some form of input protection relative to voltage and some have phase loss/distortion, the latter may need to be deactivated if there is a significant phase imbalance. The main limitation of running 3 phase VFD off of single phase is the ripple is the buss greater and thus the input circuity is more vulnerable. Many 3 phase input VFDs can be run on single phase, but they need to be derated as such. The derating factor can be modified to some degree through the use of an input reactor or DC bus choke. One also needs to consider the load on the VFD and if it is going to be pushed to its maximum continuous rating in some applications where the load is continuous. In a mill or lathe, the load is much lighter and usually not continuous so you can get by using a VFD that might be smaller than in other applications. Many VFD manufactures like Yaskawa give two VFD power ratings for a particular model, one for normal duty and one for severe duty. I think you would be fine to run a 3 phase VFD off of your RPC (this is also supported by the RPC manufactures information), you might consider going to the next size up VFD if the price difference is nominal. I have done this in a number of installs with VFDs running off of RPCs and have not had any problems, but the quality of the RPC and the phase/voltage balance may have an affect. My meager understanding of RPCs is that the more motors running off of the RPC tend to stabilize the generated leg power.

    I have not seen any VFDs that are designed for true 2 phase output, and even if it could be configured it would probably be costly. My other concern is the age of the motor, often the insulation becomes a bit more sketchy over time, so you would probably want to operate the VFD pretty conservatively (say 30-60Hz with an overload of 120%) and keep the carrier frequency at the lower end. A motor upgrade may also be a reasonable alternative if there is a suitable modern replacement, but yours seems to be a bit unusual. Interesting discussion, but I have read a few other posts through the years of others having the same experience as you.

    Instead of a 240VAC power strip, just get yourself a 2 gang electrical box and put in two duplex 240 sockets. I did this on my last mill for the axis drives in addition to a 120VAC power strip.
     
    Last edited: May 3, 2017
  29. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Apostl10 -- did your Sheldon have a three wire or a five wire? I'm having trouble visualizing how you would bridge a cap in a five wire (four hot) that is effectively two separate single phase systems chained together.
     
  30. markba633csi

    markba633csi United States Active Member Active Member

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    Randy: you would tie the two windings together in the correct phase- see my schematic above- to give 3 wires from the 4, then use a cap for the phase shift.
    Mark S.
    ps but this is just academic cuz your motor is 3 phase for sure
     
    Last edited: May 3, 2017

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