slotless brushless DC motors 1

[jag27]

Whats a good information site for slotless brushless Dc motors

i have heard the technology has been around for some time
if so why has it not been widely accepted by industry yet

or has it?

 

[jbartos]

Suggestion: Visit

http://www.manufacturing.net/ctl/index.asp?layout=article&articleid=CA269671

http://www.thingap.com/pdf/DPAMag-TG20701JM.pdf

etc. for more info
It may take some time to develop it and perfect it. Also, the market has to accept it.

 

[UKpete]

Here are a couple more manufacturers links:

http://www.eadmotors.com/products.asp?sel=Hi_Performance_Slotless_Motors_Desc.static

http://industrie.kavo.com/englisch/index.htm

- though bear in mind that manufacturers websites aren't always a source of unbiased information!

Slotless brushless dc motors are for specialist applications, either:

a servo motor requiring effectively zero cogging torque
a very high speed motor

They suit high speed operation as it is possible to reduce the iron losses, there being no teeth with high flux density, and also no slot-ripple effect to induce eddy currents in the rotor.

Despite what the manufacturers say, they have lower power density as the large effective airgap means they operate at low flux density. Also the winding is more difficult to cool.

The main manufacturing problem with them is the winding. Rhombic windings are relatively easy to manufacture but they have higher resistance - the winding does a zig-zag in the airgap, increasing its length (and taking up extra space in the airgap). Helical and especially axial windings are better but difficult to manufacture.

They are limited to fairly small machines as the winding must carry the reaction torque rather than teeth, and because of the cooling problems.

 

[SERVOCAM]

We offer slotless motors, that you can read about. I don't think we have published any technical other than what is in our catalog or in release articles.

I have worked with and sold many diffent mfgs. servo products. Slotless motor technology was not used. Many haven't adopted Segmented-Stator technology either. Slotless motors cost more to mfg and do produce less torque because ther is no iron in the stator.

We use the Slotless motors on our precision stages. Advantages are the cog-free operation and makes tuning easier. We also use slotless motor technology in our Direct-Drive and air-bearing rotary's. Nice replacement for DC-Brush motors.

I think the technology is accepted out there (but more of the lack of people knowing about it, or even needing it), a few are doing it. I think it is more that the applications just don't require it. Give it time, we will probably see more out there w/ them. Look at Segmented-Stator (Cut-Core, T-Lam), more mfgs. are changing to this technology.


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

http://www.aerotech.com

"Dedicated to the Science of Motion"

 

[jag27]

thanks jbartos, ukptet and servocam

looks like slotless would be a good fit in medical or automotive industry

 

[SERVOCAM]

I spend the majority of my time with Laser/Medical and the Data Storage industry (Disk Drive). In Laser/Medical where we are going very slow speeds and need smooth control. The Slotless motor technology is a big advantage and we can stop using DC Brush. Most that were using DC brush, are switching to the slotless motors or to brushless anyways.

Since I don't really have any automotive business here in MN, I'm not sure how/where they are being used there. Like said, the bigest advantage of the slotless motor is the zero-cog, so in contouring applications and ones that need velocity stability, they sure help (but don't forget the controls have a lot to do w/ it too).

-cam

 

[jclough]

THe slotless brushless motors we sell are used in torque drivers by the automotive industry.

Jon

 

[jag27]

what kind of a torque driver is that