Lee, I must be too young to have seen those, or else I did not have one fail because they were stronger. The other question is how does it damage the AC motor to over speed and why does a speed limiter in the controller/inverter cause damage as was indicated in the discussion? The AC motor doesn't have a commutator, or windings on the rotor so what is the harm in driving the motor to more than 8,000 rpm? All I can conceive are bearing stresses.
Dennis Lee Miles (*evprofes...@evprofessor.com <evprofes...@evprofessor.com>)* * Founder: **EV Tech. Institute Inc.* *Phone #* *(863) 944-9913 (12 noon to 12 midnight Eastern US Time)* *Educating yourself, does not mean you were **stupid; it means, you are intelligent enough, **to know, that there is plenty left to learn!* * You Tube Video link: http://youtu.be/T-FVjMRVLss <http://youtu.be/T-FVjMRVLss> * * NEW You Tube Video link: *http://youtu. be/Pz9-TZtySh8 <http://youtu.%20be/Pz9-TZtySh8> On Tue, Aug 5, 2014 at 7:43 PM, Lee Hart via EV <ev@lists.evdl.org> wrote: > Dennis Miles via EV wrote: > >> David, and others, the most fragile part, of a series DC motor, is the >> commutator. And that is, because the copper segments are glued to an >> insulating core. When the current is flowing, the segments heat up and >> soften the glue, then they are subjecting to "lifting," away from that >> insulating core, and causing problems with the brushes, resulting a need >> for an extensive repair. But, with no (or very low) current, the glue >> maintains its strength, and the motor can be spun to a higher RPM, without >> damage. >> > > Relatively new DC motors are built with commutator bars that are glued in > place. Older and heavy-duty motors instead have "steel" commutators that > don't depend on glue to to hold the bars. Instead, there are steel rings at > each end hold in the bars. They use mica or other materials to insulate the > bars. This type of commutator is much stronger, and better able to > withstand high temperatures and high RPMs. > > Here's one image I could quickly find: > > http://www.iccinternational.com/resource/vring.html > -- > We cannot waste time. We can only waste ourselves. > -- George Matthew Adams > -- > Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/ > group/NEDRA) > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140805/33830f7c/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
