tag:blogger.com,1999:blog-6231841547435511043.post5283313817409342076..comments2023-06-13T01:05:30.996-07:00Comments on The Electricle™ : Bicycle Electric-Motor-Assist Project: PMDC to Wound Field Motor? Hmmm....M.E.http://www.blogger.com/profile/15375034485988839284noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-6231841547435511043.post-92000708235884163412009-09-22T00:41:20.264-07:002009-09-22T00:41:20.264-07:00I forgot to update this with the results of the qu...I forgot to update this with the results of the question I asked over at DIY Electric Car forums. <br /><br />A knowledgeable expert there named Major gave a good concise reply that basically tells me if I'm willing to deal with a fairly complex experimental approach to figuring out what the field windings will have to be, then yes, it is possible to do. It might not end up being worth having done, however.<br /><br />I'll just link here to <a href="http://www.diyelectriccar.com/forums/showpost.php?p=139231&postcount=4" rel="nofollow">the thread I asked the question in and his answer</a>, and <a href="http://www.diyelectriccar.com/forums/showpost.php?p=130543&postcount=11" rel="nofollow">a thread he refers to there</a> that has a method by which to find some of the info I'd need.M.E.https://www.blogger.com/profile/15375034485988839284noreply@blogger.comtag:blogger.com,1999:blog-6231841547435511043.post-59150813294033518722009-08-25T21:09:57.718-07:002009-08-25T21:09:57.718-07:00Now if I could come up with a great and simple way...Now if I could come up with a great and simple way to *do* it. ;)M.E.https://www.blogger.com/profile/15375034485988839284noreply@blogger.comtag:blogger.com,1999:blog-6231841547435511043.post-75288255132403638912009-08-25T08:39:20.094-07:002009-08-25T08:39:20.094-07:00You've given a great clarification. Thanks! :)...You've given a great clarification. Thanks! :)Joehttps://www.blogger.com/profile/10265425172888920679noreply@blogger.comtag:blogger.com,1999:blog-6231841547435511043.post-36029121975904605312009-08-24T22:54:53.757-07:002009-08-24T22:54:53.757-07:00I know it will take more power to run the windings...I know it will take more power to run the windings, but I also know that with wound-field motors in larger EVs, it's possible to do more control of the motor this way. (and that the heat buildup in motors that large tends to destroy any magnets they would have had, sort of forcing their hand in generally using non-PM motors to begin with). <br /><br />Perhaps "finer" control was not the right word. <br /><br />Just using PWM can vary the control very finely even with PM motors, but there is a maximum torque that can be achieved at any particular voltage (or PWM duty cycle) based on the field magnet strength.<br /><br />If the field can be made stronger by a higher current whenever it is necessary (such as at startup), more torque can be generated. <br /><br />That's really what I meant; I should have written it out to start with. :)M.E.https://www.blogger.com/profile/15375034485988839284noreply@blogger.comtag:blogger.com,1999:blog-6231841547435511043.post-73227961847585142622009-08-24T06:14:45.241-07:002009-08-24T06:14:45.241-07:00My impression is that it won't help enough to ...My impression is that it won't help enough to be worthwhile to wind the fields with wire. It will lower efficiency, though aince those windings will dissipate power. The fineness of the control is easy to vary just through PWM on a PM motor. Mine has very fine control. It can vary continuously from zero torque to full torque.Joehttps://www.blogger.com/profile/10265425172888920679noreply@blogger.comtag:blogger.com,1999:blog-6231841547435511043.post-9679068439892771792009-08-24T02:43:46.592-07:002009-08-24T02:43:46.592-07:00There is no noticeable cogging with these PM motor...There is no noticeable cogging with these PM motors, because of the gearboxes on them. And they have just two poles, and two magnets. The only real resistance the system has is due to the gearbox design, as it is a worm gear built into the shaft that drives the other gears perpendicular to them, to give a right-angle gearbox output. <br /><br />There's a clutch pin on it that rotates to push the main output shaft gear out of engagement with the rest of the gearbox, but it can't be engaged or disengaged while spinning (it'd strip the gears). It's usually used on the wheelchair so the rider can push it manually if the batteries die, or so a helper can push to save battery power, etc.<br /><br /><br />The problem I have isn't cogging, but heat buildup, and some sort of cooling is probably going to be necessary to continue abusing the motor like this without destroying it. :)<br /><br />I'm thinking of the field windings not only to perhaps help this but also to prevent loss of torque due to heat damaging the magnets (which would no longer be there) but also to give finer control of the motor's power output.M.E.https://www.blogger.com/profile/15375034485988839284noreply@blogger.comtag:blogger.com,1999:blog-6231841547435511043.post-53062059805429805932009-08-23T09:17:52.992-07:002009-08-23T09:17:52.992-07:00If the bearings in the motors are good ball or rol...If the bearings in the motors are good ball or roller type, it could help to do that to the fields. Then cogging would disappear when the windings are unpowered.<br /><br />That trouble indicates to me that I got a fortunate find with the Pittman motors that I have, since they do not seem to suffer from the maladies that your motors do. I wish that I could send you one.Joehttp://tech.groups.yahoo.com/group/switchmode/noreply@blogger.com