Author Topic: Can we discuss electric motor modding here  (Read 1352 times)

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Harold in CR

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Can we discuss electric motor modding here
« on: January 02, 2017, 06:30:45 AM »
 He is discouraged by the less than anticipated output being produced as a typical induction motor. So, instead of cluttering up his thread, in case he hits on an acceptable solution, I would like to see if anyone here can jump on how to make this motor into a PMDC motor. It will take an inverter to run this and that is expensive and nearly unobtainium for us poor folk with no electronic experience. However, a PMDC is a doable option with readily available controllers with a little modding to them.

These are readily available, and, I have my eye on one for $50.00. I plan on buying it, IF we can come up with a plausible DIY type solution to make these work well. They are water cooled capable, and, I think they might make a great motorcycle motor. I'm off to Florida on the 10th, for 2 weeks, so, I could do some lathe and milling work and mount design up there, and carry it back with me, if a very possible solution can be decided for modding. Building the rotor is where I would like to start this discussion.

Bar magnets, curved magnets, slotted magnets, etc. canting the magnets to avoid cogging necessary ? Canting to increase the efficiency, torque, etc. ?

What do all you guys think ? Is it a viable project ?

A link to a video showing the motor in sections.  https://www.youtube.com/watch?v=n2NQ_dO3lMU

 Found some more info on this system. It is rated 15KW and 20HP capable with 79 ft/lb of torque. It is 72 Pole Stator and 56 Pole induction rotor. Supposedly it is wound "Y" and the rotor pole segments have 2 bars crossing over the Stator poles as it PULLS the rotor in the magnetic field. This is accomplished by employing a resolver for "timing" of the rotor and stator.

Now, I'm trying to figure out how many magnets would be needed in the rotor. I see the steel rotor has canted bars, so, I'm assuming the magnets should be canted also ?

From my understanding, converting a normal automotive alternator to permanent magnet, an Aluminum rotor body can be used and the magnets need an iron backing to carry the flux. The iron needs to be minimally as thick as the magnets.

My research is looking for information if permanent magnets at the highest rating of "pull" or lifting power (if that's how magnets are rated) say 50 will enable this motor to produce more torque and possibly a small increase in RPM's. I would think 20 HP would be sufficient for a 250cc or less bike conversion, but, torque seems to not be enough, according to the other thread by e-vector.

Found out that the e-assist started in 2008-2009 in the Saturn Vue hybrids. Looks like GM took a normal large case alternator and produced the e-assist from the designs adding the square wire hairpin design and making a rotor with MAGNETS. Thus, converting a later version to Permanent magnet looks very doable.

Now to see if I can find physical dimensions of both alternator motors, and, MAYBE gather magnets from older versions to put into newer version.

 If this is in the wrong place, feel free to move it.  Thanks, Harold


 

joestue

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Re: Can we discuss electric motor modding here
« Reply #1 on: January 02, 2017, 05:35:56 PM »
Fundamentally you have a problem with permanent magnet motors for Ebikes and cars, without transmissions you have a wide range of voltage produced by the motor. the rpm speed limit is set by the battery voltage. also at high speed you have a lot of eddy current losses because you can't weaken the magnetic flux.

now there are ways to weaken the magnetic flux but no easy ways to retrofit an induction motor with magnets and add field weakening capabilities.

so, induction motors remain a fairly effective motor for vehicles. their intrinsic lower efficiency and power density compared to permanent magnet machines is well known problem, but the better steel, much higher copper fill density in hybrid cars has kept them competitive.

so i would leave it as an induction motor.

if you can't re purpose the inverter that the vehicle used to drive that motor you will need to build your own. it appears to be designed for hundreds of amps, and that's what it will take to get significant horse power out of it.

btw, that appears to be an 8 pole induction motor.

Harold in CR

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Re: Can we discuss electric motor modding here
« Reply #2 on: January 02, 2017, 08:55:20 PM »

 Thanks for your input, joestue. Much appreciated.

Harold in CR

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Re: Can we discuss electric motor modding here
« Reply #3 on: January 03, 2017, 08:28:20 AM »

 joestue, just for my understanding, I found out the GM alternator motor uses a technology that PULLS the rotor around vs PUSHES the rotor around.  Would this help any in the power output of PM vs induction.

 I understand what you wrote before. I am just curious why GM decided to do this. Is it to control the total output so it doesn't charge too much to the battery, maybe ?

Warpspeed

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Re: Can we discuss electric motor modding here
« Reply #4 on: January 03, 2017, 02:51:19 PM »
Most common types of induction motors work on the repulsion principle.
Its much easier to induce very high eddy currents into a squirrel cage type of solid rotor and these eddy currents in turn produce their own repelling field which is where the torque comes from.  But there must always be relative motion between the rotating field and the rotor, which is where "slip" comes from.

Its only synchronous induction motors that have either permanent magnets, or a wound rotor with slip rings that combine attractive and repulsive forces. That in itself offers no real advantages except for constant rpm with zero slip.

Harold in CR

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Re: Can we discuss electric motor modding here
« Reply #5 on: January 03, 2017, 03:58:29 PM »

 OK. I understand what is happening, now. Thank you.

joestue

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Re: Can we discuss electric motor modding here
« Reply #6 on: January 03, 2017, 04:50:16 PM »
It makes no sense to me to describe an induction motor stator as "pulling on the rotor" because the rotor is a net consumer of energy.


If I hold a magnet next to a plate of aluminum, I have to push on the magnet to drag the aluminum around. induction motors are basically the same thing. the iron in the rotor is to make the magnetic field go where you want it to, the motor will work without it.

so anyhow, a number of automobile manufacturers are using synchronous reluctance motor. basically you have magnets, and you have a steel magnetic path. you get additional torque from the steel magnetic path through the rotor. for these motors, it may be appropriate to describe the stator coils as "pulling" on the steel core of the rotor.

see here https://youtu.be/uLNINuNwOhQ?t=806
i recommend watching the entire series.

Harold in CR

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Re: Can we discuss electric motor modding here
« Reply #7 on: January 05, 2017, 10:40:37 AM »

 Tried to watch the video, but, with wife watching TV, talking on the phone and asking me questions, I had to give up.  ::)  Have it bookmarked for later viewing under different circumstances.  Thanks for the link, joestue.