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T-Mobile. America's First Nationwide 4G Network. ------ Original message------ From: Konstanty, Walter (GE Energy Management) Date: Mon, Jan 26, 2015 10:28 AM To: RJ Kanary;Elec >> et; Subject:Re: (ET) Replace a lift strap, motor, etc.... Guys, While you are correct that series motors will overspeed if unloaded, that is assuming there is amperage available but these smaller motors have enough armature reaction and losses that it's hard for them to do so..... with that said, don't try it at home... you can damage the motor brushes or commutator and make it useless. Running a series motor at higher voltage also increases the speed proportionately. Fortunately, the lift motor is a simple motor and the increase in loading will hopefully not exceed the thermal rating of the motor. Smelling "odors" is probably varnish and not real good on the motor so don't push them. I'm retiring from GE after 37 years in the motor division this week.... new email will be Walter Konstanty outlook com . It's been a good career and plan to do more with Elec-tracs and accessories in the future..... ....Walt-----Original Message-----From: RJ Kanary [mailto:rjkanary consolidated net] Sent: Sunday, January 25, 2015 10:15 PMTo: Elec >> etSubject: Re: (ET) Replace a lift strap, motor, etc.... My Dad told me of horror stories that occurred when some of the shaping and processing equipment at American Bridge would suddenly unload a series motor. Like large rotating pieces of it taking off and leveling several walls before stopping......THEN the motor came apart.RJOn 1/25/2015 9:42 PM, David Roden wrote:> On 25 Jan 2015 at 20:45, Chris Zach wrote:>>> The RPMs really don't go up much under no load, as the series field >> plus the series armature cancel each other out.> No, they don't. A series motor MUST have a load. Operated at > nameplate voltage without any load, it will speed up until it flies apart.>> As a series motor's speed increases, the current it draws decreases. > Since current is the same everywhere in a series circuit, the field > current falls, and so does its magnetic flux. This makes the motor speed up even more.> And that, folks, is how runaway happens. If you're lucky, the motor's > case will keep the shrapnel from ripping holes in YOU.>> For testing an unloaded series motor, you can only apply a fraction > (maybe> 10%) of the rated voltage without danger of runaway.>> I suspect that the reason an unloaded ET lift motor doesn't overspeed > is that the worm gear wastes a bunch of power, ensuring that the motor > always has at least some load.>>> David Roden - Akron, Ohio, USA>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = => Note: mail sent to the "etpost" address will not reach me. To send me > a private message, please use the address shown at the bottom of this > page : http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = > = = = = = = = = = = = = = =>>>>> _______________________________________________> Elec-trak mailing list> Elec-trak cosmos phy tufts edu> https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak>>---This email has been checked for viruses by Avast antivirus software.http://www.avast.com_______________________________________________Elec-trak mailing listElec-trak cosmos phy.tufts.eduhttps://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak_______________________________________________Elec-trak mailing listElec-trak cosmos phy.tufts.eduhttps://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak |