On Mon, 2007-10-22 at 23:20 -0500, Jon Elson wrote: > Kirk Wallace wrote: > > I have a Pacific Scientific R46GENA DC brushless servo motor that I > > would like to use for my Bridgeport conversion, so I am looking for a > > amp/driver to drive it. > > > > The specifications are on page 26 here: > > > > http://www.pacsci.com/support/documents/pc800/svomtrs.pdf > > > > I don't know if it is a sinusoidal or trapezoidal motor so if anyone has > > a way to determine this, please let me know. Is the difference in the > > drive just software? > > > Looking at your link, it says they are sinusoidal.
Shoot, I thought I looked, but I guess not hard enough. > In theory, > if the drive is software-controlled, then it is just a software > setting to go between the two commutation schemes. > > If in doubt, hook an oscilloscope to the windings and turn the > motor by hand. If it gives a very sinusiodal-looking trace, > there's your answer. > > The specifications indicate an RPM of 1,700 at 240 Vac, 320 Vdc and 16.5 > > Amps max., so I assume that I need a 320 Vdc 20 Amp motor supply? > > > > The motor has only Hall sensors. Do the Hall sensors have an analog > > output in order to be able to position the rotor at a desired angle from > > the sensors? > > > No, they are actually redundant, since they only give very > coarse position info for 6-step commutation. All drives for > sinusoidal motors need to see the encoder info, and therefore > need to be programmed with how many poles the motor has and how > many quadrature counts/rev. > > Could the Pico Systems PWM brushless amp be used as a basis for my > > application? In other words, could I change the power components to > > higher voltage/current? > > > In theory, yes, but it would require replacing the "catch" > diodes, power FETs, bootstrap diodes, snubber caps, main DC > filter caps (both film and electrolytic). I think that covers > all the parts. The FET drivers are good to 600 V. That seems reasonably doable. > But, these are trapezoidal drives, they have no "software" to be > adjusted, and only look at the Hall signals for knowing when to > switch windings. I have run them on motors with sinusoidal > windings, and they hum quite a bit at low speed. I have no idea > what level of vibration you would get on a machine tool, but I > don't think it would be acceptable. So, with a trapezoidal drive and trapezoidal motor, how is the drive able to control the output shaft position to fractions of a degree? Opps, in thinking about this question and checking the brushless amp documentation, I may have just answered it myself. The brushed and brushless amps function in the same way, and have the same subsystems, but with one the activated windings are determined by carbon brushes and copper fingers, and in the other, magnets and Hall sensors. Either drive could not care less what the shaft position is. I viewed trapezoidal and sinusoidal motors as slightly different variations of each other, but they are very different. With that in mind, I am guessing, the sinusoidal motor was invented so that a stepper-like driver which does care about shaft position could be used. So, all or most sinusoidal drivers have step/direction inputs and trapezoidal drives PWM/direction and the similarities in the motors is coincidence? If this is true, then I am way out of luck as a far as drivers/amps for my PacSci motors. I do have Rutex drives for my Sanyo's, but I don't have a good feeling about support, let alone getting creative with applications. Any one have thoughts on this drive? http://granitedevices.fi/index.php?id=8 It too is a little shy on current and voltage. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe Bridgeport mill conversion pending Zubal lathe conversion pending) ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
