Differences between different makes of servo-motors

[MarH]

I'm purchasing a brushless servo-motor for some experiments, and I'm having a hard time deciding between different makes.

I can find models from Kollmorgen Goldline XT, Pacific Scientific PMA, Parker BE, and others that all match the required specs with similar prices.

Is there any particular advantage to any of the makes, or are they pretty much the same?

 

[jbartos]

Suggestion: One way to go about this dilemma is to ask the manufacturers for the product reliability data, e.g. Mean Time Between Failure (MTBF), Mean Time To Repair (MTTR), Life-Cycle, etc. Other way may be to ask for references from “satisfied Clients.

 

[wwilson]

Compumotor satisfied client here. I've been impressed with Compumotor products since the BE product line. Emailing questions to Pac. Sci technical support is a waist of time -they say contact the distributor. I know Kollmorgan, Pac-Sci, and others are all owned by one company now, and we've been worried about what will be available in the future - what kind of consolidation is going to happen? That said, all the mfg's you listed have been around a long time, and should have good products. In general I think the drive/controller side of the equation is more important if you stick with "standard" three phase, encoder based servos.
Depending on your business, you can probably get a consignment unit to test - we've tested all the one's you listed on consignment in the past. Good Luck, wwilson

 

[jbartos]

Suggestion: A first line of technical support is not necessarily very sound or strong. The second line, perhaps from the manufacturing environment is somewhat better. When it comes to product applications, they are often very difficult for everyone. It just depends on the application level of difficulty.

 

[avigodner]

Another arguments for brushless motor / drive selection may be:
- torque ripple at low speed;
- torque-speed area (torque available at high speed);
- motor thermal behavior / efficiency / loss including that induced by PWM inverter operation;
- advanced drive features like phase advance for torque-speed area enlargement (torque for loss trade-off at high speed); automatic phase search (initial phasing) at start-up (power-up) for AC brushless with incremental encoder in the absence of Hall sensors etc.

For some more info see "PWM Loss" and "Smart Initialization" articles overviews at

http://www.drbrushless.com.

 

[jbartos]

Suggestion: In addition to the above. The closer application fit is always better. This includes but is not limited to:
1. Suitable speed toque characteristics for the anticipated experiments
2. Adequate controls
3. Excellent protection because of experiment applications that may be demanding
4. Availability of parts and tech support
5. Etc.

 

[SERVOCAM]

They are pretty much all the same. It usually comes down to who has the features you need...and for the right price. I use to sell Motion Control product for 12 different manufactures...it is usually the delivery & support that makes the difference.

As Jbartos mentioned "Adequate Controls" or more the fact that typically you don't just buy the motor...you need the drive/amplifier to go with it and possibly the controller as well.

Someone mentioned about the Kollmorgen & Pac-Sci now being owned by same company and what will be around in the future. This is a good point as I was screwed over by this company acquiring and obsoleting product overnight.

Maybe some cosiderations are narrowed down by your application, such as motor package size, need for cog-fee (low torque ripple). Some use different technologies on how they make the motor. For example, Segmented Stator technology (also known as cut core) vs. Stuffed motors. A segmented stator motor will produce 30 - 40% more torque in a 30 - 40% smaller package size than your traditional stuffed motor. Some motors are also a slotless design (such as my BMS motor). It has no iron in the stator, therfore no cogging and no torque ripple (no detent torque). Other things are feedback device. What resolutions can you get, do you need absolute encoder. There is also environment considerations that set some apart - High Temp or Water-proof, or Explosion-proof.

In general, all the mfgs you named are good. I have ran into them all and have worked with many as well. Here are some more to look at:
1. Emerson Control Techniques
2. Baldor Motion Control
3. Rockwell - Allen Bradley
4. Yaskawa
5. Indramat
6. Exlar
7. Infranor
8. Simple Servo (not make own motors)
9. Automation Intelligence (Sanyo Denki)
10. Ge Fanuc / Whedco
11. Aerotech - me

It usually comes down to (other than price) who has the best local support because most are sold through distribution.


Cameron Anderson - Sales & Applications Engineer
Aerotech, Inc. -

http://www.aerotech.com

"Dedicated to the Science of Motion"