[NWBEST]

Hi,

Newbie here with a stepper motor question.

I have 2 Vexta Nema 34 (Unipolar 6 wire) motors that I would like to connect to a Gecko G540 using the "half coil" method.

The voltage/amp/inductance ratings appear to be within the G540 guidelines

I can't run them full coil, since the inductance is way too high (24)

I planned on using them for my dual Y ballscrew axis...so the loss of torque will be acceptable.

Has anyone had any experience with this?

Any advice is appreciated :-)

according to the Oriental motors website...it looks like the all the Unipolar specifications are exactly the same as half coil configuration.

I've been researching this for a while already...I really want to run the G540

link:

Customer Service and Technical Support

I'm really hoping to use these motors...(budget constraints)

Holding Torque
Bipolar (Series) 880 oz-in
Unipolar 620 oz-in

Connection Type
Bipolar (Series)
Unipolar

Current per Phase (A/phase)
2.1 [Bipolar (Series)]
3 [Unipolar]

Lead Wires 6

Voltage (VDC)
6 [Bipolar (Series)]
4.2 [Unipolar]

Resistance (Ω/phase)
3 [Bipolar (Series)]
1.5 [Unipolar]

Inductance (mH/phase)
24 [Bipolar (Series)]
6 [Unipolar]






They are Heavy duty steppers, and planned on using them for my DIY Router/Mill build (Machine 75% done)

I picked them up a few months ago (local surplus), and would really like to use them...if it's realistic.


Machine build (28x32 cutting area)
THK HSR35 rails for X,Y,
dual NSK ballscrews for Y.
NSK screw & THK SHS25 for Z (haven't assembled the Z yet)

Rest of machine is built out of 1/2" aluminum plate & extrusion (very heavy/sturdy)

I plan on primarily working with wood, but I'm hoping My build will have the tolerance to do light milling/engraving also.

[H500]

The half coil performance will be the same as unipolar. The match is not ideal. 6 uH of inductance is quite high. The ideal should be closer to 2.

6 uH of inductance is high. The ideal should be closer to 2 because speed is more useful than high torque. I'm using 283 oz-in steppers for my sx3 mill, which has a 120lb head and dovetail slides.

[NWBEST]

Thanks for the feedback.

I realized that 24 uH was crazy high, but I didn't think 6 was unrealistic.

I factored this in using the Keling Nema 34 465 oz as a guide (4.2 uH) from Automation Technologies

These were "specifically designed" for use with the Gecko G540, so I didn't think going up to 6 was a huge deal.

At this point I would like to get the 'beast' to move...without doing any immediate upgrades (well over a yr long project already )

I am willing to sacrifice speed for torque (for now...budget), but I just don't want to do anything stupid that will cause an electronics failure.

I can always upgrade the motors down the road(maybe servo if I win the lottery ;-), but I've already set it up for Nema 34 mounts regardless of the initial motor selection.

Thanks again,

Jeff

[Toinvd]

If speed is not the most important, go for these motors . They will do the job, and like you said, later on you can always update the motors. The Gecko drivers will accept many motors.
This way you will get your project running. Connect them using the "halfcoil" way and the electronics will work fine.

[H500]

Some unipolar motors can be rewired (internally) as bipolar parallel. That will give you around 40% more torque, assuming the drivers can handle the higher current. However, you will most likely not need the extra.

[NWBEST]

I appreciate the advice!

I think I will use the Older Vexta PK299-02BA unipolar motors for now, and upgrade later...if needed.

I have actually already researched the option of re-wiring the unipolar motors to use as bipolar, but I found little info on this procedure

It didn't look to be too difficult, after removing the caps

Anyone done this with a Vexta motor?

Thanks in advance!

[H500]

It's easily done as long as the wires are accessible after the end cap is off. You will see the point where 2 enamel wires are joined together and brought out as one. Simply break the joint and add an extra wire to each phase.

But don't pull the rotor out or it will lose part of its magnetism.

[NWBEST]

Ok...I will pop off the cap of one this weekend, and take a look. If I decide to re-wire it, I'll post a couple of pictures for others interested in modding a unipolar motor. Thanks!