I need some AC Servo Motor Education

[jim_geib]

I need some brushless AC Servo motor education.


I pickup a brushless Ac servo motor and a Pacific Scientific controller this week. I did a quick web search before buying and they seem to match. My question is the motor is sped'ed at 750 Watts. I converted that to HP on Google converter and it came back as 1 HP. Is this right, this motor is about 4”
sq. and maybe 6”-7” long and that includes the encoder. That seems to be a lot of HP in a small package.

Thank You
Jim Geib
Masfield, Ohio

[Hood]

Yes that will be correct, the AC servo I have just put on the spindle of my mill is approx 5.5" square and 12" long inc encoder and it is 7.9Kw (10.5HP approx)
AC servos pack a punch for sure :)
Hood

[jim_geib]

Yes that will be correct, the AC servo I have just put on the spindle of my mill is approx 5.5" square and 12" long inc encoder and it is 7.9Kw (10.5HP approx)
AC servos pack a punch for sure :)
Hood
Thank's Hood

This could be fun I have a 1/3 HP DC motor on my Smithy now and also have all three axis under Mach3 control. If I can get everything to work a nice indexable spindle motor. there is also the 1500 Watt Ac servo I picked up the same day, but I think it will need a bigger controler than the one I got. I got all this for $110.00. Oh how I love good shop time in the winter :)

Thanks again

Jim Geib

[Hood]

I replaced the 11Kw induction motor on my lathe with a 12.5KW AC Servo and would hate to have to go back. The Induction motor worked through a gearbox that had electromagnetic clutches for changing gear but it meant you only had set speeds like on a manual lathe, with the servo I can tell it to do any speed I want and CSS is now possible :)

Hood

[macona]

I have a 750w servo on my little hercus as well. Really nice.

Note that Mach does not support positioning the spindle on a lathe (C Axis)

Also you need to do research when looking for a drive for a motor. You need to know what kind of feedback your motor has and also what the voltage of the coils is.

[Hood]

You can position the spindle in Mach if you have a stepper or a servo, you use the SwapAxis() feature and that will make the spindle act as a rotational axis. Unfotunitely at this point its not implemented in the SmoothStepper, not sure about other external hardware but it does work well with the parallel port. It can all be done in Gcode via a custom macro.
I am not sure but I suspect this may be the way industrial CNC machines handle spindle positioning as well, just you know nothing of it as its done automatically.

Hood

[jim_geib]

Macona,
I have a Pacific Scientific PC830 drive. This is my first experience with AC servo motors and I just might let the smoke out. I have Googled and Googled and read everything I can find on these thing and they just might work. Heck this is all surplus stuff and it may not work to start with, but it is still fun playing with. I have a good sized pile of “OH WELL THAT DIDN’T WORK” stuff.

Hood,
Thanks for the hint on SwapAxis()

New Queston:
On the encoders the pin out has A and an A with a minus sign above the A . The drive schematic is labled as :Encoder Input Channel A (+) and Encoder Input Channel A (-). Would the A with the minus sign above it be the (-) wire?

[john buck]

A question for Hood:
What did you do about cooling for the servo motor. I would very much
like to hear what you did about that. Thanks

[Hood]

Hood,
Thanks for the hint on SwapAxis()

New Queston:
On the encoders the pin out has A and an A with a minus sign above the A . The drive schematic is labled as :Encoder Input Channel A (+) and Encoder Input Channel A (-). Would the A with the minus sign above it be the (-) wire?


Yes thats correct.



A question for Hood:
What did you do about cooling for the servo motor. I would very much
like to hear what you did about that. Thanks

Nothing, AC servos usually dont have a problem with cooling as the windings are in the body rather than the armature so are in effect self cooling as the heat dissipates through the aluminium casing.

Hood

[macona]

Macona,
I have a Pacific Scientific PC830 drive. This is my first experience with AC servo motors and I just might let the smoke out. I have Googled and Googled and read everything I can find on these thing and they just might work. Heck this is all surplus stuff and it may not work to start with, but it is still fun playing with. I have a good sized pile of “OH WELL THAT DIDN’T WORK” stuff.

New Queston:
On the encoders the pin out has A and an A with a minus sign above the A . The drive schematic is labled as :Encoder Input Channel A (+) and Encoder Input Channel A (-). Would the A with the minus sign above it be the (-) wire?

Looks like it could be a pretty nice drive. It looks like it can handle encoders or resolvers. Just set it up with the software. What motor do you have?

Heres an app note about connecting it to drive with an encoder with commutation feedback.

http://www.pacsci.com/support/documents/hallnote.pdf

A and /A is usually how its notated in text. Encoders come in basically two varieties, single ended and differential output. In a single ended encoder there are two wires for power and ground and one wire for each track. Most encoders have two tracks A and B. Some encoders have an index track labeled I or Z. The output on these lines is referenced to ground.

Now differential encoders (Also know as line driver) work a little differently. Instead of one wire per track there are two wires per track. The output on the second wire is opposite of the A wire. So the wire with a / above it means that that is the inverted complement to the other signal.

So what does this get us? Differential signaling allows long wires with good immunity to noise. You can often have data rates double or more than a single ended set up.

So what do you do when you have a drive or receiver that is expecting a single ended encoder when you have a differential encoder. Forget about the inverted outputs, thats what. Put a bit of shrink tubing over the end and just connect the main wires.

Now if it the other way around where you have a differential input on the drive and a single ended output on the encoder you might be in for a little more difficulty. You will need to use something like a am26ls31 line driver IC to convert the signal from single ended to differential.

[jim_geib]

Mancona,
The 750 Watt Motor is:
Sanyo Denki
BL Super P3 AC Servo Motor
Model P30B08075DXS11
3000 RPM – 8 Pole – 2000count Encoder

The other is:
Toshiba
RA12M
Model 12M2-1500R
It has what I think is a resolver, I peeked under the rear cover plate and found a Tamagawa Seiki resolver
http://www.pacsci.com/support/documents/hallnote.pdf

I think this motor is two big for the Pacific Scientific drive as I am limited to 120 V. Single phase in my shop.
Thank for the additional information

Thanks
Jim Geib

[macona]

Running a motor on low voltage will just limit the max RPM of the motor.

First thing you need to do is find data sheets for the motors. You will need the info in there to program the drive to handle the motor correctly. You need info like phase resistance, inductance, inertia, and other fun stuff.

[jim_geib]

Mancona

Thanks, time to return to Google and see if I can dig out this information.

[jim_geib]

Thanks Guys, as of last night I have the motor turning. I finally got the wiring done and brave enough to flip the switch. Glad to say there was no smoke cloud, motor did not turn, but after playing with a few configurations I have the motor at least turning over. It runs rough but runs; now I can start all the seemingly 5 million different setting to get it smoothed out.
Thank again to all that posted and kept going in the right direction.

Jim Geib

[macona]

If its running rough the timing is probably off.