[CNC] Has anyone any experience with 5 phase steppers?

E

Erx

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A local garage sale netted me some large stepper motors - but they are 5 phase (5 sets of windings). This seems pretty unusual, so I wonder if anyone has ever used something similar or seen an application, or drivers, or even software written for a 5 phase stepper? If the model number matters, I'll list them, but a web search only returns a few hits.

Thanks,
rex
 
Rex,
Stepper motors are brushless, so the use energized poles to move the rotor. I would suggest that you read a document on steppers called "Jones on Steppers" available all over the web and at the Univ of Iowa site also. The number of poles in a stepper determines the resolution that you can gain by lessening the movement of the rotor for each energized pole. Once you have read the article on steppers and still have questions do not hesitate to ask and we will get you turned the right was pretty easilly.
Bob
 
As far as software goes, I believe mach3 would be able to handle the math. I'm not sure about controllers though, which i believe is the more pertinent question. The software just figures out steps per table movement, the controller needs to relay that to the 5 poles. I'm not up on the capabilities of controllers.
 
If it has 5 wires, that sounds like a unipolar stepper motor. They're the easiest to drive. Simply find that wire that reads a resistance to all of the other ones. That's the common. That can be tied to your supply voltage (or to ground). The remaining four wires are connected to the other supply (+ or ground depending on what you've connected your common wire to). Each wire get's connected (only one at a time) 1,2,3,4 to the other supply to step the motor. Doing the same thing 4,3,2,1 runs the motor the other way.

A 5 wire motor (really only 4 phases) is the same as a 6 wire motor except two wires are connected internally to bring 5 out.

See here. http://www.stepperworld.com/Tutorials/pgUnipolarTutorial.htm

The other main type (apart from three phase steppers - not normally seen in commercial applications) is the Bipolar (AKA two phase, sine-cosine, or 4 wire stepper motor). These need to commutated by connecting each wire to positive or negative in a specific sequence. This is normally done with a circuit called an H-bridge. Bipolars offer the advantage of more torque in a given size, and the ability to be microstepped. Microstepping offers the ability to position the motor in between detents (as long as power is on).

Unipolars can not be microstepped easily if at all. They are also larger for a given torque because only 1/4 of the available copper is used at any time. There is a way to get 1.4 times the torque, but the motor will step in between detents and power must be retained to maintain position. The big advantage to unipolars is the ease of commutation.

My company designs and builds custom brushless DC and stepper motors for space applications and I design the motion controllers for these radiation filled environments. Stepper motor drivers and applications are my area of expertese.

If it has 5 sets of windings (ten wires) that's a horse of a different color. It could actually be a 5 phase motor (VERY uncommon) or two unipolar motors sharing one rotor. These can be used individually for reliability by redundancy or connected in parallel or series for higher voltage or higher current applications (usually seen only with Biploar motors)

John
 
If there are 10 wires coming out, take a voltmeter and try to figure out which wires are connected to which. If you have 5 pairs of wires connected, then yep, you probably have a 5 phase motor, something I didn't even know existed...

In that case, I think you are going to have a problem finding an off the shelf controller to handle that. If you are handy with electronics, you could probably put a controller together. Its a bit of work, but doable.

If the motor has 5 wires coming out, it's probably not a 5 phase motor. More likely it is a regular unipolar stepper motor with the center taps tied together. Recall that in a unipolar motor you typically tie the center tap to ground, so it doesn't matter that they are tied together. I don't think you could run a motor of that type with a bipolar driver.
 
A unipolar motor does require a different driver then a bi-polar. Both are readilly available on the net and from Spark Fun and other hobby vendors. The key to steppers is pulse sequence and speed. Remember that steppers lose a lot of torque at higher RPM which is counter intuitive when working with electric motors. The stepper motors strongest point is the ability to move a certain number of steps and hold that position. Most specs on steppers that say 1054 inch pounds or whatever are giving you the holding torque of a fully energized motor and NOT the actual torque the motor will develop. Gecko makes a very good drop in controller with great tech support and the pres of that co. answers his own phone when you call. They have probably the best cust service I have ever encountered in an electronic/electrical supplier. Geck also has a site at Yahoo groups.com that will assist with resolution of issues prior to calling tech support. The Gecko co. owns that list and monitors it as well. I use steppers on my CNC plasma table and my automated Z axis and have a plan in the works right now to add a stepper drive to my 3-n-1 machine for long travels and slow repeatable surface finishes.
Bob
 
Rbeckett said:
A unipolar motor does require a different driver then a bi-polar. Both are readilly available on the net and from Spark Fun and other hobby vendors. The key to steppers is pulse sequence and speed. Remember that steppers lose a lot of torque at higher RPM which is counter intuitive when working with electric motors. The stepper motors strongest point is the ability to move a certain number of steps and hold that position. Most specs on steppers that say 1054 inch pounds or whatever are giving you the holding torque of a fully energized motor and NOT the actual torque the motor will develop. Gecko makes a very good drop in controller with great tech support and the pres of that co. answers his own phone when you call. They have probably the best cust service I have ever encountered in an electronic/electrical supplier. Geck also has a site at Yahoo groups.com that will assist with resolution of issues prior to calling tech support. The Gecko co. owns that list and monitors it as well. I use steppers on my CNC plasma table and my automated Z axis and have a plan in the works right now to add a stepper drive to my 3-n-1 machine for long travels and slow repeatable surface finishes.
Bob
Click to expand...

Good point Bob. The advertised value for torque is usually the powered holding torque. All motors have a torque speed curve where available torque falls off as some function of speed (ideally linearly, but other effects enter in to make it non-linear).

For a stepper motor, the torque falls to zero and the motor fails to run "in sync" at the speed where torque generated by the windings are unable to overcome the detent torque + hysteresis + viscous damping + friction. All of the above losses are speed independant except for viscous friction. That's why strange things happen when the motor loses sync and it jumps around, runs, runs backwards (when the commutation sequence comes back around).

The torque constant (Kt) is usually also specified: where torque is motor current times Kt. This is only true with a stepper motor at the beginning of a step however.

Do you have a picture of this motor?

John
 
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I have to ask fellas. Where was this info when we were going over stepper motors in the Basic CNC Thread.

"Billy G" :banghead::headscratch:
 
i wonder if the extra 2 wires may be a temp sensor/thermal limit like some dc motors have?
steve
 
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