3 servo motors - What are the actual specs?

[Bloy2004]

I just received these servo motors in the mail and since I have only one power supply(for my Shoptask 3in1)which has gecko320s, I interchanged the y axis motor with one of these and after tuning, the motor seems to run the axis without problem though maybe just a little slower.
I was wondering if I can do this safely(the motor didn't get warm) as these motors are rated at 30.3 volts whereas my power supply is 39 volts from Camtronics. If this works, then I can interchange the controller /drivers by only unpluging from one machine to use the other,while having separate configurations as is available in MACH2.
As long as I don't overload the motors, set limits on the geckos, and keep the rpms up, will there be harm inflicted on the system?

If these ARE 1800 rpm motors, what does that do to the other specifications as listed below in subsequent posts.
I'm feeling I made a good buy for the medium-weight(now that's relative) router that I am collecting parts for...is this true?
..or did I overpay?

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWN%3AIT&rd=1

Any responses welcome

[sendkeys]

hehe no way of knowing. seen some people do it with no problem others fry and die

But if you drop the amps try to keep the watts about the same it should work. This will give you more rpm but less torque so it would only be good if you do a belt ratio

ghetto idea but you can always wire in power diodes in series for .7 voltage drop

got a suprlus store around you migh tbe cheap idea.

[Bloy2004]

I suppose I should have mentioned that I tested it with a 3.5 to 1 belt reduction and a 5tpi screw. The original motor that it replaced on the shoptask's y axis had a 1000 rpm at 39VDC. These "shorter" motors have less power obviously, as it faulted out unless velocity settings were slightly reduced. This is where the slower ipm setting in the tuning of the motor was required. The only way I could get it to fault then was to apply execessive drag to the handwheel attached to the ballscrew.....a vulnerable resistance point.

[Bloy2004]

I have no way of knowing, at this time, of what the oz/in peak torque rating is..... It doesn't match any of the listed motors at the GLOBAL site mentioned in the e-bay auction....
.. so I am wondering what that actually IS....the peak torque.

Here is a spec sheet that has the closest match in red..but the seller says that they are 1800 rpm motors...and the number on the motors is 537A274 ....of which I can find no information.

[Bloy2004]

And here is a diagram of the motor dimensions.
They are fitted with :
Encoders are US digital E2-512-250-P Standard TTL quadrature type with 512 counts per revolution.

Can anyone tell me why these are 1800 rpm motors? and what does that do to the specifications listed above.? Where can I find specs on this motor numbered 537A274.

I guess I need to invest in some test equipment and learn how to use it!

[Bloy2004]

Here's a pic of the label on the motor.....

[HomeCNC]

It looks like a good deal. These motors will seem like they turn slower compaired to your Poly-Sci ones for one reason these have twice the amout of encoder counts on them. Each pulse moves 1/2 the distance of your other servos.

The most important thing to find out is the peak Amps of the ebay servos. If they can handle the 20 amps of your Poly-Sci ones then the samp power supply will be fine.

[Bloy2004]

Thanks Jeff!
About those amps(20 of 'em) ...Is it true that only the amps that the motors need are drawn? So if the load never exceeds the motor's max amps, they may never receive the full 20 amps. and too, if the motors are set to fault(or the drives) at a preset load, does this qualify as a "safety zone" for the motors?

I guess what I'm trying to do is make my controler/driver/power supply to be utilized for both machines. This would save the costs of an extra power/driver supply...when i get the router built. The "station" could then be castered across the room to operate in the wood area as opposed to the metal area.
I'm thinking that the router I'm working on will hardly experience the heavy loads in the metal lathe/mill.
...and too I have a 7x12 minilathe/mill combo that i'm testing and think these motors will fit on this machine as they have a small foot print...although they may have unnecessarily too MUCH power for the small machine.
Bloy

[Bloy2004]

Thanks for your insight, Sendkeys. I may need those diodes/resistors to make the station easily adaptable for each machine.

[ESjaavik]

That 30.3V seems a bit funny. They surely won't run for years then blow up the second you exceed 30.3V. The motors usually have a design RPM, to which corresponds a certain voltage when no load is applied to the shaft. The RPM is directly related to voltage as long as the load torque stays the same. When you have a controller governing the speed, you just limit the RPM to the design RPM within your control program, and that's taken care of. Then it is no problem that the voltage into your drives are higher. In fact it's better when it is as long as is don't exceed the safe voltage that the motor insulation can take, and you should have plenty headroom with 40V.

Skip diodes and resistors, but mount the drives so you can easily change the current setting when moving to the other machine (if you find a different setting is called for).

But you should limit current so that your motors don't overheat. Start with a low current setting. If following error is too great, increase it. If the motor is too hot to touch after working against a heavy load (like rapid back and forth moves at high acceleration), decrease it. If your following error is too great, and you can't increase it because motor overheats, it's too small for the application.

Yes, your drives will only feed enough amps into the motor to make them follow the commanded speed. The motors can take several times the rated amps if it only happens intermittently and the load inbetween is low. Not unlimited however, there is a limit you should never exceed because it will demagnetize them.

A bit oversimplified I'd say voltage give you speed, and amps give you torque, but of course in real life neither speed nor torque requirement is constant, so they interact.

[Bloy2004]

Thanks ESjaavik

After your response i'm feeling confident to move on. Sooner or later I will determine the actual specs of these motors. The overload issue is now just something to keep in mind.....maybe temperature sensors mounted on the motors with audible alarm for early warning....