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. 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. 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. > Is a continuous stall torque of 7.6 Nm (67.3 lb*in), and a peak torque > of 20.2 Nm (179 lb*in) appropriate for a Bridgeport? It is probably overkill, even for high performance machining. Assuming direct drive to a 5 TPI leadscrew, that will deliver 5629 Lbs of linear force. Can your screw and bearings handle that much force? Even at the continuous rating, it is 2116 Lbs. I am using 9 In-Lb PEAK motors with a 2.5:1 belt ration on my Bridgeport. With the belt ratio, it delivers 22 In-Lb, and I have NO PROBLEM with that. It can still snap off a 3/8" cutter in the spindle without tripping the servo amps! (Don't ask how I know this!) My plan is to have > a direct coupling between the motor and ballscrew. I have some Sanyo > P5's but at 3.9 Nm (46 lb*in) continuous and 11.7 Nm (139 lb*in) peak > torque, but they seem a little small. > 46 In-Lb still gives 1446 Lbs of linear force. Have you ever seen the SEM motors Bridgeport uses in the Ez-Trak? I'm pretty sure they are NEMA 26 size motors about 5" long, probably weigh 10 Lbs. They do use a modest belt reduction with them. Jon ------------------------------------------------------------------------- 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
