I have a Rivett lathe that uses a motor generator to supply the DC for the motor. That's a PITA. I have a rotary converter to generate the three phase to drive the motor generator to create the DC for the motor.
When I was in the motor shop getting the commutator on the motor reworked, I spoke to someone there about what I was using the motor for. They had an off the shelf solution that took 120 or 240 (I forget which it was or whether it could work on either) in and generated DC for both the field and armature windings of a DC motor. It seemed to have variable speed control and was intended for this application. I believe the price was between $100-$200 dollars. (My motor is a 2HP.) I decided not to go that way because the lathe has a very nice bidirectional rheostat/reversing switch that I wouldn't want to replace right now. Also, the lathe doesn't get heavy use. If I ever convert to CNC, I'll look at that. Someone on some list suggested that DC motors have much better torque/horsepower curves than a corresponding 3ph motor with a VFD. That's another reason to stick with the DC motor. Ken Kenneth Lerman Mark Kenny Products Company, LLC 55 Main Street Newtown, CT 06470 888-ISO-SEVO 203-426-7166 ----- Original Message ----- From: "Gene Heskett" <[EMAIL PROTECTED]> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Sent: Friday, May 02, 2008 11:02 AM Subject: Re: [Emc-users] Off Topic, DC Spindle Motor > On Thursday 01 November 2007, Kirk Wallace wrote: >>On Wed, 2007-10-31 at 20:15 -0600, Jon Elson wrote: >>> Kirk Wallace wrote: >>> > What is the best way to drive a 4hp, 90VDC, 40A spindle motor on a >>> > Hardinge CHNC? Some of the large DC motors I have seen, look like >>> > universal motors which would operate on AC or DC. Does anyone know if >>> > the CHNC spindle motor could work on AC? I'm thinking, a few dimmer >>> > switches in parallel and a stepper to turn the dials ;). I wonder if >>> > it >>> > would be cheaper to go with a 3-phase motor and VFD. Thanks. >>> >>> No, these motors are NOT universal motors. You could rectify >>> the mains to drive the motor, but then it would draw 40 A from >>> the line. You should be able to find an SCR drive for this. >>> You can't parallel dimmers, they can't be trusted to give the >>> same pulse width. >> >>I was joking about the dimmers. So far I have found this: >> >>http://www.baldor.com/products/detail.asp?1=1&page=1&catalogonly=1&catalog=B >>C155&product=DC+Controls&family=One+Way%7Cvw%5FDCControls%5FOneWay&voltage=1 >>80 >> >>but this puts out 180V and I need 90V. Plus it seems that this kind of >>controller does not interface with a computer well at all. It's >>beginning to look like DC lathe spindle drives are a specialty item, >>which means, hard to find and big bucks to buy or repair. >> >>> If it is a standard-frame motor, then you >>> could go the 3-phase and VFD route. That may not give you the >>> range of speeds and torque required. >> >>The newer VFD's are much better with this aren't they? >> >>> If you want smooth, >>> controlled reversing, then you need a DC servo drive. If you >>> don't need a complete 4-quadrant servo drive, then the SCR DC >>> motor drives may be the way to go. Baldor and plenty of others >>> make these, they show up on eBay all the time. >>> >>> Jon > > Hey guys, even the lowly board out of a Harbor Freight 47xx8 micromill, > except > for the current rating, makes a truly excellent vsc when combined with a > PMDX-106. > > This board, with a much larger bridge rectifier replacing its puny 4 amp > device, and about 6 of the mosfets it uses in parallel with smallish > current > sharing R's in series with the src's of each of the devices could probably > do > that just fine. The speed control is very stiff with this unit, so stiff > that if I'm doing something heavy, I have to rig an ammeter in series with > the motor in order to see how close I am to the 'red line'. Otherwise it > just blows the fuse with no detectable motor slowdown first. > > The only problem that I could foresee might be related to this boards > ability > to drive that much gate capacitance of the paralleled mosfets and still > achieve good switching speeds. It is something I have not played with > personally, so one might approach this by adding one device at a time & > watching the heating. Running correctly, the mosfets shouldn't heat more > than 10F if screwed to a good heat sink and delivering 50% of their rated > current. In my own case, that would be at least 10 amps, but I didn't yet > replace the puny bridge rectifier either. Mine is currently in a closed > plastic box with the PMDX-106 and has run that way for half a day at a > time > without the box getting noticeably warm. The direction relays make as > much > heat as the rest of the circuitry. > > -- > Cheers, Gene > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Rule #1: > The Boss is always right. > > Rule #2: > If the Boss is wrong, see Rule #1. > > ------------------------------------------------------------------------- > This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > Don't miss this year's exciting event. There's still time to save $100. > Use priority code J8TL2D2. > http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
