On Mon, Apr 29, 2013, at 06:00 AM, andy pugh wrote: > On 29 April 2013 06:33, Cecil Thomas <wctho...@chartertn.net> wrote: > > > > My only > > real concern is going to be integrating spindle speed control because > > the existing control utilizes two huge rheostats to control the drive > > motor field and the generator field. I might just lash up a servo or > > stepper with a belt to the control knob. > > In your position I would be strongly tempted to remove the whole Ward > Leonard setup, probably offering it to someone wanting to repair their > lathe.
I'm not sure I would be so quick to discard the Ward Leonard setup (and I design electronic motor drives for a living!) The Ward Leonard setup is very rugged to overloads and other abuse, and probably provides a much better speed/torque curve over a wider range then you would get with a VFD and an AC motor. > You seem to have a single phase supply spinning a 3-phase idler motor > spinning a second three phase motor spinning a generator spinning a DC > motor. > > The Ward-Leonard arrangement is fairly elaborate in itself, but > running it from a rotary phase converter is just excessive. Agreed about the phase converter part. I'd be tempted to investigate spinning the generator with a single phase motor, or simply adding caps directly to the electrical box on the lathe so that the existing three phase constant speed AC motor will run (at reduced power) on single phase. > It has to make more sense to couple a 3-phase motor and > single-phase-input VFD directly to the spindle? Before you do that, carefully study the speed/torque capabilities of the new system and compare them to what the factory system can deliver. A 3HP AC motor driven by a VFD can deliver 3HP at the nominal speed of the motor ONLY. Below nominal speed (also known as base speed), the torque is constant, and the power thus drops off linearly. At half speed, you only get 1.5HP. At 1/4 speed, you get 3/4HP. Above base speed there is usually a modest "constant power" range, maybe 2:1, over which you can get roughly 3HP (typically the power drops off slowly even in that range). Above that range power drops off rapidly. And most AC motors are not designed to run above base speed at all. DC motors also have a base speed, and also deliver constant torque below base speed. But they can have a much wider constant power range above base speed. The engineers at Monarch almost certainly chose that DC motor to have a very wide constant power range, and the gear/pulley ratios were chosen so that the motor runs above base speed (in the constant power region) most of the time. Discarding the DC motor will almost certainly mean a significant performance penalty. Keeping the DC motor and driving it with either a DC drive, or the existing motor-generator set, will keep the performance. > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > ------------------------------------------------------------------------------ > Try New Relic Now & We'll Send You this Cool Shirt > New Relic is the only SaaS-based application performance monitoring service > that delivers powerful full stack analytics. Optimize and monitor your > browser, app, & servers with just a few lines of code. Try New Relic > and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- John Kasunich jmkasun...@fastmail.fm ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
