Bipolar Series or Parallel Modifications


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Thread: Bipolar Series or Parallel Modifications

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    Default Bipolar Series or Parallel Modifications

    I realize that you can buy an 8 wire motor and wire it in series or parallel, but has anyone ever taken a 4 wire motor and opened it up and been able to change it to a parallel configuration? Assuming of course, that it was wired in series to begin with?

    I'm looking to see if anyone has done this, hopefully with pictures, and what estimations were used about how this would change the performance graph of torque vs speed, also required current, voltage, etc.

    Is possible? Is not possible?

    Any feedback would be appreciated!

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    Default Re: Bipolar Series or Parallel Modifications

    just take the end off and leave the magnatised multipole rotor inside the laminated body so it acts as a keeper
    (I have read with some motors, the rotor will loose some of its magnetism if you remove it !)

    as for being easy to rewire the coils It depends on the stepper motor
    and how the coils are connected

    The one motor I replace the connecting wires had a printed circuit board that would of made it easy as all the ends of the coils was soldered to the PCB

    if its like this picture found on the web
    Bipolar Series or Parallel Modifications-wiring-inside-stepper-motor-jpg
    it does not look like its that easy

    John

    PS





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    Default Re: Bipolar Series or Parallel Modifications

    Thank you for the reply!

    No, it doesn't look easy, but it also doesn't look impossible. A couple of snips here and there and rewiring the connections between the windings......I don't know. I have to think that some one has done this?

    I was watching an old video on youtube yesterday, where someone said that the rotor would loose 2/3 of it's magnetism if you removed it. I just find that really hard to believe. I'd have to look to see if I can find that video again. Of course, if it can be done, I don't see why you'd have to remove the rotor as you suggest, leaving the rotor in place for the rewiring.

    Thanks again for the reply. Hopefully someone will know of an example where this has been done, or know of an easy way to splice the thin coated wires that go between the windings. Perhaps there are specific connectors that can be crimped in place?



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    Default Re: Bipolar Series or Parallel Modifications

    I had motor with bad bearing so I took it apart and fixed the bearing. After it turned but lost all its power so it was a fail.
    I had 3 6 wire motors and I locked the shaft in a vise with wooden jaws so when I removed the back plate the spindle was locked in and could not move.
    I then found the center tap and unwound it to get 2 coils. I used heat shrink tubing to reconnect and insulate the wires. There is not enough room to use connectors.
    I also used electrical varnish to insulate and lock in the wires.
    I put the back plate on without ever moving the motor.
    These motors were faster in bipolar parallel than they were prior in serial ( the only option with 6 wire motors)

    I would say you are gambling to do this and I was willing to except failure.

    What makes you think your motor has 4 coils and is wired in series.

    To see the effects if you can do this find an 8 wire motor that has the same specs as yours in serial and look to see what it is in parallel.

    George



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    Default Re: Bipolar Series or Parallel Modifications

    It's hard to find the graphs. I sent an email to longs motor and asked them for the graphs for some of their 8 wire Nema 34's wired in parallel. Let's see if they respond.......

    Do you know of any graphs that show an 8 wire motor wired in series and also in parallel?

    I assume that it's wired in series based on the characteristics of the torque vs speed graph. I don't actually know. I'm just looking for general options to reduce the torque at low RPMs and increase the torque at high RPMs as well as maximum speed.

    Yes, it's a risk. I could destroy the motor I try this with. Perhaps I should try this with a cruddy old cheap motor that no one wants from somewhere.



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    Default Re: Bipolar Series or Parallel Modifications

    Gerry

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    Default Re: Bipolar Series or Parallel Modifications

    Quote Originally Posted by ger21 View Post
    Check Oriental Motor, they may have some.
    That's a good tip! They post all their graphs. I like that. Thank you.

    3.35 in. (85 mm) NEMA 34 PKP Series 2-Phase Bipolar Stepper Motors On Oriental Motor U.S.A. Corp.

    I have to wonder if some of those motors are the same, but one wired in series and one in parallel? They are all 4 wire. But some of them are very fast running on 80V with a higher current draw, when the graph for the lower speed motor is run on 24V, but lists a different current/phase and has a different part number.

    Still, Oriental motor has some fast stepper motors. Their 906 oz-in PKP299D63AA looks like quite a versatile motor.

    Quote Originally Posted by ger21 View Post
    I've always assumed that 4 wire motors were the same as parallel, but could be wrong.
    I don't think so. I think it depends on the motor. 4 wires could be either or. I had a look at primopal. They list the differences in mH and Amps when wired in parallel or series for their 8 wire motors. I send them a message requesting some graphs. Long's motor never bothered to reply to me.

    That 1600 ozin motor that people often buy from EBay with an inductance over 20mH. I'm pretty sure that one is wired in series. Looking at primopal, they have a similar one, and the inductance changes to about 5mH wired in parallel.

    I have no idea which one is more common, but I assumed it was series based on the fact that they all seem to end at 1000 RPM, whereas some stepper motors can push over 2000 RPM, like the one I mentioned from Oriental motor, so I again assumed this was wired in parallel.



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    Default Re: Bipolar Series or Parallel Modifications

    Quote Originally Posted by ger21 View Post
    I've always assumed that 4 wire motors were the same as parallel, but could be wrong.
    Quote Originally Posted by NIC 77 View Post
    I have no idea which one is more common, but I assumed it was series based on the fact that they all seem to end at 1000 RPM, whereas some stepper motors can push over 2000 RPM, like the one I mentioned from Oriental motor, so I again assumed this was wired in parallel.
    I've found some graphs of 8 wire in parallel. I believe that you are correct, and they are almost all wired in parallel. If it is wired in series it will have a very high mH value, like the 1600 oz in one mentioned previously. That's probably series, but it looks like the other 99% of 4 wire steppers are probably bipolar parallel to begin with.

    The graphs of the 8 wire wired in parallel that I've been looking at, well, most end at 1000 RPM or so. It looks like the key to speed is a very low inductance value.

    The fast oriental motor stepper, PKP299D63AA

    Item # PKP299D63AA, 3.35 in. (85mm) 2-Phase Bipolar Stepper Motor On Oriental Motor U.S.A. Corp.

    has an inductance of 2.6 mH / phase and a resistance of 0.32 Ohms / phase. Also, the graph for that motor can be found on this page:

    3.35 in. (85 mm) NEMA 34 PKP Series 2-Phase Bipolar Stepper Motors On Oriental Motor U.S.A. Corp.

    And the graph shows it being run at 80VDC. Well, that flies in the face of the Gecko step motor basics max voltage = 32*sqrt(inductance). That would give a max voltage of 51 Volts. So, I'm super not impressed with Gecko's step motor basics at the moment. Where does this maximum voltage come from? Oriental Motor is running this stepper at 80 Volts! Who is correct?

    Well I actually have some CNCRP Nema 34 motors, and those have an inductance of 2mH and a resistance of 0.32 Ohms / phase. I wasn't actually thinking of trying to modify those motors, but;

    Can I run those at 80V and expect similar performance?



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    Default Re: Bipolar Series or Parallel Modifications

    Gecko's formula was created by them, based on many years of experience.

    If you read Gecko's white paper, they mention that when increasing the voltage, you'll reach a point where you can no longer keep the motor cool. Keeping the motor cool is the issue here.
    Larger motors can dissipate heat better than small ones, so can usually run safely at higher voltages. And mounting motors to a large aluminum plate also helps draw the heat from the motors.
    And finally, the drive plays a large role here. Better drives keep motors cooler.
    My 570oz Nema 23 is 2.5mH, which gives 50V with Gecko's formula. I have a 60V power supply. I've had the motor powered up for over 30 minutes, and it's only gotten slightly warm. I have the current reduction set to 30%, to help keep it cool.

    Gerry

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    Default Re: Bipolar Series or Parallel Modifications

    Quote Originally Posted by ger21 View Post
    Gecko's formula was created by them, based on many years of experience.

    If you read Gecko's white paper, they mention that when increasing the voltage, you'll reach a point where you can no longer keep the motor cool. Keeping the motor cool is the issue here.
    Larger motors can dissipate heat better than small ones, so can usually run safely at higher voltages. And mounting motors to a large aluminum plate also helps draw the heat from the motors.
    It seems like such a wag of an equation from Gecko that everyone (including myself) has taken as gospel truth. Oriental Motor is fine with it at 80Volts according to their graphs. Also a Nema 34. I also was emailed some graphs from Primopal. They have a motor on one one graph with 110 VDC input, but the gecko equation says it should be maxed at around 70V. I don't know. Still not impressed with Gecko. I may just try an 80V power supply, oh wait, hmmm, not sure at exactly what voltage a G201X will pop. It says up to 80VDC, not sure if it will destroy right at 80 or if there is some leeway. Also looking at some leadshine products.

    It just seems kind of stupid to me that I was thinking of buying some Oriental Motor steppers, but I probably have the exact same thing sitting beside me, but I never considered it before based on Gecko's equation.

    Quote Originally Posted by ger21 View Post
    And finally, the drive plays a large role here. Better drives keep motors cooler.
    My 570oz Nema 23 is 2.5mH, which gives 50V with Gecko's formula. I have a 60V power supply. I've had the motor powered up for over 30 minutes, and it's only gotten slightly warm. I have the current reduction set to 30%, to help keep it cool.
    That's a good point. Thanks for posting! It sounds like I can push the voltage higher.



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    Default Re: Bipolar Series or Parallel Modifications

    Geckos should be fine at their rated voltage. I seem to recall that the components they use are good to 100V. And if you blow one up, they'll replace it for free.
    Gecko's have always been considered the top brand in the hobby community, until the Leadshine digital drives arrived on the scene, and gave them some competition.


    Remember that torque charts are made using a specific drive, at a specific voltage, and a specific microstep setting.
    Change any one of those, and the graph changes.
    I think of a torque curve chart as a ballpark number, and actual results may vary.

    Gerry

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