>>Wonder why they headline the power rating of the motor, rather than the torque of the motor, since torque is what we are mostly concerned with when it comes to the use of the motor?
It is about the same thing as rating a motor in horsepower. At a certain power - Torque and RPM are interchangeable to some extent via gearing. Most smaller servo motors tend to run fast - 3000 rpm in the case of that 400 watt motor so usually gearing or a belt reduction is required to take advantage of the power available. The best thing to look at are the speed-torque curves. I don't know if there is a link to them from the Machmotion website. I found them on the TECO website before. That way you can determine exactly how much torque you can get out of the motor at a given speed. As Andy said though, the torque curve is pretty much flat on these motors all the way out to their rated rpm and then it falls off. Those motors will actually spin at speeds greater than the rated speed but at reduced torque. If you compare the torque - speed curves of a brushless industrial servo motor/drive to a stepper motor drive, you will find the differences are startling. If you want to do a comparison just for reference - look up the speed torque curves for the Automation Direct servos - at AutomationDirect.com and compare them to a stepper motor - you can find some speed torque curves at Kelinginc.net. Here are some links: A Stepper motor.. the bottom is in Pulses per second - half stepping so I think that is 400 pulses per rev for most bipolar stepper motors. http://kelinginc.net/KL34H295-43-8BT.JPG http://www.automationdirect.com/static/specs/sureservolow.pdf Look at page 2 in this PDF file for some speed torque curves. That speed-torque curve on the Keling website is really a best case situation since they are using a high voltage stepper drive in that speed-torque curve. Most people use lower voltage drives on steppers - like the common Gecko drives. Mariss of Geckodrive has said before that in general if you need more than 200 watts of power in an axis you should consider a servo drive. I believe I have seen Parker docs that indicated that they can get as much as 400 watts of power out of a stepper but to do that they use a high voltage stepper drive. If you look at the speed-torque curves of the stepper motor you will see why steppers do their best at lower speeds. Dave On 8/11/2011 6:59 AM, Mark Wendt wrote: > On 08/11/2011 06:49 AM, andy pugh wrote: > >> On 11 August 2011 11:39, Mark Wendt<[email protected]> wrote: >> >> >> >>> So, that, and looking at some of the other servo motors and how >>> they convert, gives me about a .739 conversion factor to go from watts >>> to oz-in and a 1.353 conversion factor to go from oz-in to watts. A >>> watt is a unit of power though, so does it always translate that nicely >>> for torque factors? >>> >>> >> No, I am afraid that is a totally spurious calculation. >> >> You need to compare power with power, and torque with torque. >> >> > That's what I figured. Wonder why they headline the power rating of the > motor, rather than the torque of the motor, since torque is what we are > mostly concerned with when it comes to the use of the motor? > > Mark > > ------------------------------------------------------------------------------ > Get a FREE DOWNLOAD! and learn more about uberSVN rich system, > user administration capabilities and model configuration. Take > the hassle out of deploying and managing Subversion and the > tools developers use with it. > http://p.sf.net/sfu/wandisco-dev2dev > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
