On Tue, 2012-03-06 at 04:22 -0800, charles green wrote: > what are the differences between one phase motors, two phase motors, and > three phase motors?
Generally, single phase power can be described with a single sine wave. The sine wave is the voltage measured between L1 and L2 on the mains and in the US is 220 to 240 Vac. 110 or 120 Vac is also single phase but the sine wave is derived by L1 and N (Neutral) or L2 and N. The most basic single phase motor might have a rotor with a North and South pole and a stator with a single N and S. One way to visualize this is in considering a drive wheel, push rod and piston of a steam engine. The piston can only push and pull in one direction and the wheel can spin in either direction. Single phase motors need some sort of starting feature to get the motor rotating in the proper direction. Also, they use two power wires and a safety ground wire. Two phase power generally has two phases that are shifted time wise by 90 (and 270) degrees or a quarter wave length. There are two separate phases, so four wires are needed on the motor. A piston engine configured in a 90 degree V would be similar. Motors and engines will start and run only in one direction. Some early power stations provided two phase power but this didn't last long. Two phase is now most commonly used on stepper motors. Three phase power has three sine waves shifted by 120 degrees. With this timing, three phase power needs only three wires, L1, L2, L3, instead of six wires if the phase timing were shifted by 90 degrees as in two phase described above. This, most likely, is why two phase mains power didn't last very long. A radial engine with three pistons spaced 120 degrees apart would have the same push-pull forces on the crank shaft as on the three phase motor rotor. As with two phase motors, the motor will start and run in only one direction. As always, Wikipedia has a lot of information on this: http://en.wikipedia.org/wiki/Single-phase_electric_power http://en.wikipedia.org/wiki/Two-phase_electric_power http://en.wikipedia.org/wiki/Three-phase_electric_power -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ 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
