[swarfmacdaddy]

HELP!!!! Someone please! I have a Harbour freight mill that i cnc retro'ed and here are the specs. Sanyo Denki Step syn motors, model# 103-845-6741 nema 34 frame, 12 to 300 volts,6.7 amp, 8wire, holding torque 486 oz/inch. rotor inertia=21.5 oz/inch, winding inductance=2 mh. They are wired in series unipolar mode for a current winding value of 6.7x0.707=4.74 amps. I am using Gecko drives G-201's. And a lambda regulated power supply model# lq-532 That has a max output or 40 volts, 5 amps.(It list for $1300. on their website, but i got it on ebay for $100.) The computer is a e-machine with amd k6-2/300mhz with 3-d now. 32mb sync DRAM/512 kb l2 pb cache,2.4 gb hard drive,ati rageIIc agp graphic card with 4 mb sdram. And a 98 works bundled O.S. I am also using Turbo cnc V.4 The problem is low torque. I have tried parallel wiring and series. I have tried every different current set resistor. I have tried every possible pulse width in turbo cnc. As well as every parameter in turbo. When i say low torque, i dont mean it wont move the table. I can lean against the table while jogging the mill and cant stop it. BUT if i grab the handwheel it locks up and the rotors just chatter away. Mind you its not missing steps or anything like that, but i know thats not right. Everyone keeps telling me "If it works, What do you care!" But the point is, 486 once/inch motors are not printer motors and you should not be able to stop them with LIGHT pressure on the hand wheels. I would be eternally greatfull to anyone that can help me solve this problem.

[MrBean]

Looks to me like your power supply does not have enough AMPs. If 1 phase of 1 motor draws 4.74 Amps, you're near the 5 Amp limit of the PS without any other motors spinning.

[swarfmacdaddy]

One other thing i thought strange, The lable on the motor states,12/300 volts. ???? Thats a pretty big range. Anyone know whazzup witdat?

[MrBean]

You can run motors at very high voltages, (many times the rated voltage), but to aviod burning the windings out you must limit the current to that stated on the label.

If a motor is rated 5v 1A. Then it will pull 1A @ 5V. If you run 50V it will pull enough Amps to melt the winding, which is why you must limit the current to 1A.

[swarfmacdaddy]

Thanks Mr Bean, Ive heard that from more than one person. But a friend that helped me to finally helped me make the thing move said that now that its wired in series, each allowable current through each winding is half that of the parallel rated current. Here is the part thats got me confused, The documentation that can with the motors states"as a general rule the allowable current through each each winding is:for bi-polar series6.7a.x0.707=4.74 amps. For bi-polar parallel 6.7A x 1.414=9.47A were 6.7A is the unipolar rating.

[fyffe555]

Mac daddy,
Have a look at this; http://www.automotsys.com.au/SD34.pdf page two gives the torque curves for your motor at 75 and 130v. It also says they are 9.5a per phase. You'll see that to get 486oz-in you need to wire it in bipolar parallel and give them 9.5a.

Also you didn't mention at what speeds you're running these at, but the curves show the motors torque drop off fairly quickly with speed.

On the power supply Gecko recommend not using a switched power supply which is what your Lamda is.. Check the gecko site for the support documents - his stuff is some of the best. Do you notice a difference in power with one or two motors running? I think your supply is undersized..

[ger21]

Mac daddy,
Have a look at this; http://www.automotsys.com.au/SD34.pdf page two gives the torque curves for your motor at 75 and 130v. It also says they are 9.5a per phase. You'll see that to get 486oz-in you need to wire it in bipolar parallel and give them 9.5a.

You can wire it bipolar parallel OR series and still get the full torque (Well, according to the link you posted, pretty close to full torque).
You can't wire them unipolar with a Gecko, and if you look at the charts, series will give you very little torque once the motors start spinning. Usually the best performance will always be bipolar parallel wiring.

If you read the White Papers at Gecko's website, you'll see you need 2/3 of 9.5a for EACH motor, or 6.333a x 3 = ~19amps. So your 5a supply is probably only giving you 1/4 of full torque. And if you need higher speeds, you need higher voltage. Wired parallel, your motors are rated 4.27V. Series wired would be 8.54V. Gecko recommends 10x the rated voltage minimum, up to 20-25X. Your'e only running at 5x. So what you really need is a 70V, 20amp power supply to get the performance your probably expecting.You can't go much bigger because of the Gecko Max of 80V. It looks like those motors would run really good at 175V

[swarfmacdaddy]

Thanks Fyffe55, I have put the info on my motor labels into every search engine on the web,and come up short.Was that a doc you had? Also those sure are my motors,butwhy do the specs on mine not match those on the ams site? They show my motors as as having 9.5 per phase. And the labels on mine clearly read 6.7 amps. Im not running them to fast and im only cutting plastic,but id like to do it right so as to not prematureley kill my motors. How hard would it be to build a 70v 20 amp power supply? Thanks

[swarfmacdaddy]

Oh! I forget to say that im not moving any of the 3 motors at the same time.

[ger21]

The 6.7a on your label is the unipolar rating. Since the Gecko is a bipolar drive, you can't wire them that way. Your options are 9.5a parallel, or 4.75a series. If all 3 motors are connected, they're still drawing current. Steppers produce full torque without spinning. So they still draw current.

What I didn't think of earlier is that you can't supply 9.5a with Geckos. Your limited to 7a, right? That would only give you roughly 73% of full torque, or around 350 oz-in. That's before they start spinning. Then you'll have less.