3 wire stepper?
Philldapill
Posts: 1,283
Well, I haven't posted anything in a while so here it is.
I've been into controlling steppers with the propeller lately and it's gotten old. However, recently, I came upon a BIG motor of some kind that looks like a long NEMA 34 size stepper. I applied power to a pair of leads(after finding which ones) and the thing kicked VERY hard into a single position. I've found that only 3 wires form pairs inside the motor by taking it apart a bit. Anyone know anything about this? It looks like it used to have an encoder or something on it as there is a ground to the case, and two clipped wires inside that do nothing. The remaining three are what apparently energize the coils of some kind inside. Very odd.
Once I understand how the coils are configured, then the question is, building a circuit for the prop to control. I have a feeling it's not going to be simple.
I've been into controlling steppers with the propeller lately and it's gotten old. However, recently, I came upon a BIG motor of some kind that looks like a long NEMA 34 size stepper. I applied power to a pair of leads(after finding which ones) and the thing kicked VERY hard into a single position. I've found that only 3 wires form pairs inside the motor by taking it apart a bit. Anyone know anything about this? It looks like it used to have an encoder or something on it as there is a ground to the case, and two clipped wires inside that do nothing. The remaining three are what apparently energize the coils of some kind inside. Very odd.
Once I understand how the coils are configured, then the question is, building a circuit for the prop to control. I have a feeling it's not going to be simple.
Comments
-Phil
I did some testing on it, and it sems that I can get it to step by alternating the series of connections, just like a stepper. Basically, I got it to work like this: Let's call each wire L1, L2, L3. By alternating like the following, it rotates with a VERY strong holding torque.
L1+, L2-, L3-
L1-, L2+, L3-
L1-, L2-, L3+
repeat
I haven't determined the step angle yet, but it seems to be on the order of about 1.8 degrees, just like my other steppers...
So, Phil, back to the question of it being a brushless DC motor... Aren't they kinda the same?
Yes, that is true to a point. But a brush-less motor never gets to rotor lock position, the poles are changed before the armature reaches that point. So from·the control stand point they·are a little different.
The primary way of control is the same, but the timing of steppers vs. 3 phase brush-less is different.· Also, steppers from a voltage stand point are usually controlled all from positive. 3 Phase brush-less on the other hand actually swap the polarity of the windings.
So there are some differences which are subtle, but create a different animal.
James L
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James L
Partner/Designer
Lil Brother LLC (SMT Assembly Services)
If you want to use it as a stepper, I don't see why you couldn't just control it as such. It should work just fine as a stepper. I'm not sure what the angle would be per step (depends on the motor internal design), but I think it would work fine.
I figure you could control with just standard half bridge type setup......
James L
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James L
Partner/Designer
Lil Brother LLC (SMT Assembly Services)
Unless you have a use for driving the motor I would use it as a paper weight.
Graham
Regardless, this thing is a 6Nm motor of some kind and it sure does produce that much torque. If I can just control it, I can sure get alot of use from it.