Unexpected inner wiring in stepper motor
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Hello my friends,
Ive recieved new "bipolar" 4-wired stepper motors for my Z axis upgrade and it seems theyve got their inner coils all connected. My Duet 3 which im using cant drive them and prints out message "short-to-ground on drivers: xx".Ive tried to connect only one coil (2 connected wires) and it did one step, but obviously cant continue without second stepper coil. So I looked up online and from what i found it seems the stepper might be unipolar cause of its all together connected coils. Circuit diagrams with bipolar steppers only appear to be connected between two wires = one coil. I dont have stepper grounded to main frame so im probably missing something. Or can it be that it really isnt bipolar as they have said me? I got 4 and they are all the same. Same resistance across any two wires.. around few to nothing ohms...
This is the motor:
https://www.omc-stepperonline.com/nema-24-stepper-motor/dual-shaft-nema-24-stepper-motor-42a-4nm-566-ozin-60x60x100mm-4-wires-24hs39-4204d.html -
@sidsm
Maybe that's the reason, why they were in the 'clearance' section? It's not unusual for big steppers to have upto 8 wires, (2 coils with separate center wires). Maybe they mixed them up the wrong way?
Ask OMC for clarification, if they are able to replace them...if not, open them and inspect the wiring. We can help finding a solution. -
@sidsm That page says they're bipolar steppers, so there should be two independent coils.
I like stepperonline, and I think they will help you out if you contact them with this information.
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@alankilian @o_lampe All right guys, we tore the stepper apart and found this surprise (pic below). Looks like someone (or something?) drilled a hole into the coil. Odd thing is that every one of them is like that. Must have been done by machine? The thing is that we shorten one shaft before we knew so Im not sure about a refund. What a great day :DD
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Update: We fucked up. The threaded hole was without the bottom and was pointing directly to the coils... we over-tighten them and destoryed them. Nevermind xD
But still cant understand such a bad design. Who would do it like this??
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@sidsm Oh NO!
That's a shame.
I've certainly done stuff like that.
One time I was adding a handle onto a brand-new double-pane window and when I screwed it in, the screw was too long, AND was a little too high, and it screwed right into the glass and BANG! I had a US$400 repair before I even used the darn thing.
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@sidsm
It's a first time for everything...
I'd take it as an opportunity to rewind the coils, but I've done that as a hobby and later as a profession.
Maybe you digg the challenge? -
Done this twice on a 1K high output alternator ..... with the screw that holds on the temperature probe. Just a tad too long
Didn't realize what had happened until after the alternator was repaired and the dang thing failed a second time. I think this was my most expensive screw up (pun intended)
In my case there was no neat evidence after the fact. The screw shorted something but when removed for repair there was no evidence other than the blown diode stack. -
@sidsm can you show the motor faceplate? I’m confused, because the picture on the stepperonline page doesn’t show any hole over the coils. Did you drill those yourself?
Ian
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@sidsm said in Unexpected inner wiring in stepper motor:
Update: We fucked up. The threaded hole was without the bottom and was pointing directly to the coils... we over-tighten them and destoryed them. Nevermind xD
But still cant understand such a bad design. Who would do it like this??
What were you trying to attach to the back of the stepper?
