so the motor in, say, a small drill press or a _bench grinder_ is probably of the resistive start winding type?
it would be nice to turn the rpms on a bench grinder way down for final figuring of certain cutter edges, to reduce removal rate, reduce heat at the cutter edge, and reduce innaccuracy from vibrations. brushed ac motors are easy to turn up and down, but have a large defect of set point compliance with any loading, especially at lower rpms. (..and they are noisy.) any ideas? reversible would be nice too, to improve the lathe toolpost grinder for example. (dremel type tools work ok for small small small stuff, but tend to have really sloppy bearings. (..and they are noisy.)) --- On Tue, 3/6/12, Jon Elson <el...@pico-systems.com> wrote: > From: Jon Elson <el...@pico-systems.com> > Subject: Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11 > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Date: Tuesday, March 6, 2012, 10:13 AM > charles green wrote: > > what are the differences between one phase motors, two > phase motors, and three phase motors? > > > > > > > A single-phase motor needs something to get it started, as > there is no phase > rotation to cause the rotor to start turning. There > are shaded-pole motors, > resistive-start, capacitor start, > capacitor-start/capacitor-run motors and > capacitor-run variations. > These generally have centrifugal starting switches that shut > off the > start winding > when the motor is up to speed. The shaded pole and > cap-run motors do > not have the starting switch, though. The resistive > start winding or > the capacitor creates a phase angle shift that provides the > rotation for > starting. > So, all of these except the shaded-pole are actually > two-phase motors, but > they generate the 2nd phase internally. > > One problem with these motors is they are much less amenable > to variable > speed operation. When equipped with a starting switch, > then you can't > run it below the speed where the switch turns on the start > winding, as > it will overheat the start winding. When equipped with > a capacitor, > the proper phase angle shift is only obtained at one > frequency. > > You won't find true two-phase motors run from the power line > except > in the most unusual cases. However, a stepper motor is > usually a two-phase > motor. > > Three phase motors have 3 sets of windings arranged around > the stator, > and the phase sequence provides the rotation for > starting. So, no > capacitors or switches are needed for starting, making the > motors > much simpler and more reliable. Since there are no > special arrangements > for starting, these motors are much easier to operate off a > variable > frequency > supply to get variable speed. The voltage applied > should be proportional > to the frequency. > > Jon > > ------------------------------------------------------------------------------ > Keep Your Developer Skills Current with LearnDevNow! > The most comprehensive online learning library for Microsoft > developers > is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, > CSS3, MVC3, > Metro Style Apps, more. Free future releases when you > subscribe now! > http://p.sf.net/sfu/learndevnow-d2d > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
