260 Flyer Posted January 29, 2009 Share Posted January 29, 2009 For a brushless outrunner, is the number of poles, the number of windings or the number of magnets? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 29, 2009 Share Posted January 29, 2009 The pole count usually refers to the number of "teeth" on the stator onto which the coils are wound - these are almost always in multiples of 3 ( 'cos our brushless ESC use 3 wires ) so you end up with stators of either 3 6 9 12 and so on. HTH Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted January 29, 2009 Author Share Posted January 29, 2009 Thanks Timbo Quote Link to comment Share on other sites More sharing options...
Ron van Sommeren Posted January 30, 2009 Share Posted January 30, 2009 Sorry Timbo, not the teeth/slot count but the magnet count is the number of poles. That's the number (some) controllers need to know. Prettig weekend Ron Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 30, 2009 Share Posted January 30, 2009 Yes Ron I know that the magnet count is needed by the ESC to set timing correctly etc, but that wasnt quite what was asked. To quote Brian Mulder When you start looking for stators for motor building purposes, you will notice that they come in all sizes and pole counts. The pole count is the number of teeth available for winding coils on. For our purposes, a stator must have a number that is divisible by 3 in order that they can be used with commercial speed controllers. So this would mean that stators with 3, 6, 9, 12 etc are useable. Seems to be some confusion here Ron Quote Link to comment Share on other sites More sharing options...
Ron van Sommeren Posted January 31, 2009 Share Posted January 31, 2009 Yes, two kinds of poles. That's why I also write it in full: magnetpoles, statorpoles. When the polenumber of magnets is mentioned in an ad on a manufacturers site, it always refers to magnetpoles. It is never the number of windings however. Vriendelijke groeten Ron Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 31, 2009 Share Posted January 31, 2009 I think Rob needs to clarify his question a lttle further then Ron Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted January 31, 2009 Author Share Posted January 31, 2009 Sorry guys, I was a bit vague. My question was in regard to the number of poles to enter into my Eagletree e-logger to give a sensible RPM readout. If I enter 12 for the number of coils I get a reading about 15% higher than I would expect. If I enter 14 for the number of magnets the mean speed seems about right but the trace develops so much noise it is hard to read. Quote Link to comment Share on other sites More sharing options...
Ron van Sommeren Posted February 1, 2009 Share Posted February 1, 2009 It's the same as for the number of poles for a controller, you have to enter the number of magnetpoles, not the teeth/statorpoles/slots. A magnet passing a coil generates a voltage pulse in that coil. The controller detects and counts those pulses. The number of magnetpoles passing a coil per second is an indication for rpm. If you enter 12, the datalogger divides the number of pulses by 6 to get revs/sec, if you enter 14, the number of pulses gets divided by 7 to get revs/sec. Hence the difference of 15%, it all adds up very nicely If the noise is too bad, just keep on using 12 (or 10) and subtract 15% (or 40%) of the reat out you get. Some manufacturers (e.g. www.flyware.de & www.rs-e-motoren.de) use tiled/cascaded magnets in their biggies to create one larger single magnet from several smaller ones to get a better fit in the bell. That larger magnet still counts as one magnetpole. Only for motor-builders/winders is the difference between statorpoles and magnetpoles relevant (it determines the winding diagram), for all other e-flyers poles = magnetpoles. Vriendelijke groeten Ron tiled/cascaded magnets from www.solcon.nl/gjkool/ Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 1, 2009 Share Posted February 1, 2009 Hi Rob - for the logger its the magnet count you need.....sometimes I have to peer through the end bellhousing and try to count 'em - many mototrs do not state the magnet count at all ! Thanks for that excellent data Ron Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted February 1, 2009 Author Share Posted February 1, 2009 Thanks Guys I would need to dismantle my big turnigy to count the magnets, so I think I'll buy an optical tacho, counting prop blades is much easier! Quote Link to comment Share on other sites More sharing options...
Ron van Sommeren Posted February 1, 2009 Share Posted February 1, 2009 Before you honour your Philistine inclinations, what Turnigy would that be? Link? Maybe I can give you the number of magnets (probably 14 anyway), without you having to tear it apart. Careful when sliding the bell back on, very strong magnets, don't let the bell slam home. Bad for your ball bearings. Better use an extra pair of hands. Vriendelijke groeten Ron Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 1, 2009 Share Posted February 1, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 1, 2009 Share Posted February 1, 2009 Yes - this can also shatter magnets in some cases Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted February 2, 2009 Author Share Posted February 2, 2009 I just keep my fingers in the way - that cushions the blow. Fingers return to a normal colour after a month or so! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.