# PM motor question



## elevatorguy (Jul 26, 2007)

Anyone have any information on overvolting a PM motor? 
I have a 24 volt motor and want to run at 36 to 48 volts.
Is there enough flux in the magnets to make this work?
Ideas and advice appreciated.


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## Greenflight (Sep 13, 2007)

It's never a really good idea to push any motor beyond its ratings... it can be done though, especially with lower duty cycles than those specified.

I would think the only concern with a PM motor (besides the usual concerns shared with say, a series motor) would be degaussing of the magnets due to heat. Over time, if you pushed the motor beyond its ratings, you'd probably lose power.

Just my best guess.


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## Wirecutter (Jul 26, 2007)

I ran a $900 Perm PMG-132 at 72 volts on a 300A controller. It came apart after less than 8 hours of service. Don't do that.

I've spoken with another guy that put 700A into a PMG-132. His only lasted 10 minutes.

Perm-mag motors are more efficient, but Perm motors (at least) are babies and can't take any punishment. YMMV.

-Mark


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## MarshallMiller (Feb 6, 2008)

Could you be more specific when you talk about punishment?


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## Wirecutter (Jul 26, 2007)

Well, I home-built a couple of gokarts. My philosophy has been that, if I can build it, I can fix it. So I drive them pretty hard. See here:

http://www.youtube.com/watch?v=RTdbjXOa-BU

I've heard from a couple of others that have used the Perm, and they've had failures similar to mine. The consensus I've gotten is that the Perm really can't handle more than about 200 amps. I have 300 amp controllers in both of my karts.

The failure mode is like this: There are clips on the outer peremeter of the armature that apparently connect the winding "halves" together. These clips will come loose if they get even a little hot. When this happens, they rattle around inside the motor, shorting other windings together. This shorting blows out the contacts on the commutator. Photos:


















In the top photo, you see the clips, with the one that got loose there on the table. If you look closely, you can see where it came from. The second photo is the commutator blow-out.

-Mark


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## MarshallMiller (Feb 6, 2008)

I watched the video. Thats some nice punishment. What kind of runtime do you get on that cart?


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## Wirecutter (Jul 26, 2007)

Heh, heh. I can get 40 minutes driving as hard as I can, but more normal "track" type stuff can last an hour. That's using a D&D ES-33, which is what I used to replace the Perm.

-Mark


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## Dennis (Feb 25, 2008)

I sure would like to race my Advance DC motor powered go kart against yours. LOL. It would be a nice race.


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## Wirecutter (Jul 26, 2007)

Dennis - Is it possible that I know you? Do you live in South Carolina by any chance?

A race would be a hoot. My latest adventure is zipping around the paved golf cart paths on the local golf course. If you can find a similar course without golfers on it, I recommend it. With the weather around here as cold as it is now, I've been able to get away with it a couple of times.  It's like a miniature grand prix track or something. I'm sure if my kart was gas powered, I would have been discovered and chased off. It's so much fun, I'm positive it's illegal.

-Mark


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## Dennis (Feb 25, 2008)

Yeah thats me. My motor is no longer stock as Jim tapped holes for 5 degrees of advancement which I have notice a speed boost! I am going to try field weakening next to see just how far I can take my kart's top speed with current setup. 

I have my eye on this kit when I have the funds to upgrade: http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac-induction.php

8000 RPM should put me in the shifter kart territory.


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## Wirecutter (Jul 26, 2007)

Well damn, Dennis! Thanks for that link. As it happens, I have also been investigating 3ph induction motor drive. That last setup, although expensive, looks like just the ticket. Whatcha gonna use for batteries?

-Mark


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## Dennis (Feb 25, 2008)

The batteries I am using are cheap 33 AH wheel chair batteries with the name brand "Werker" on them. I don't get anywhere near the runtime that you do. I am hopeful that I can find a supplier who can sell high quality 55 AH lead acid batteries from stock rotation from being on the shelf to long.

You are going to use the last setup! One hundred five foot pounds would make your kart very adrenaline pumped to ride. Never mind the burnouts, just imagine the whiplash from that much torque!


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## Wirecutter (Jul 26, 2007)

Whoa, not so fast. I said I was _investigating_ three phase IM. I need to develop a case before trying to clear that kind of expense with the CFO.

What I _have_ done is invested in some development hardware for 3 phase induction motor controller design. Microchip (no affiliation, etc, etc) has a lot of good information on designing such motor controllers, and complements it with hardware. What convinced me that it might be worthwhile to get all this stuff is that they also give you free detailed circuit descriptions, and I can actually read and understand the stuff. Frankly, I'm impressed that they're willing to put so much effort into getting engineers to design their microcontrollers into products.

The way I've been saying it is like this: I _know_ AC motor controller design is not trivial - certainly not as simple as a DC controller. (Ok, yeah, let the flames begin... ) The thing is, I haven't convinced myself that it's too difficult for _me_ to do. It's off to a slow start, but I think it can be done. Should I succeed, I haven't decided if I want to either commercialize it (less likely) or put it out "GNU" style. Putting a design out there for all to see has the potential advantage of getting lots of eyes on it and helping to iron out problems.

I think 3 phase AC is the way to go for EVs. Take the example of AC Propulsion (Wrightspeed X1, TZero, Tesla), the EV1, the Electric Ranger, and the local subway. Subjectively, 3PIM controller is no more complicated than a modern cell phone - probably less so - and look at what volume has done for the cost of cell technology. Wouldn't it be neat if that happened with 3PIM technology? Ok, it's a stretch, but I can dream... 

-Mark


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## Wirecutter (Jul 26, 2007)

Dennis said:


> You are going to use the last setup! One hundred five foot pounds would make your kart very adrenaline pumped to ride. Never mind the burnouts, just imagine the whiplash from that much torque!


 While I haven't _decided_ to get one of those, I certainly have _fantasized_ about it. Ohhhhhh, yeaaaaaah.  I've been running the numbers - I realized that if that last setup could do 105 lb/ft AND 8000 rpm at the same time (which it doesn't) , you'd have:

105 * 8000
-------------- = 160 HP
5252

Imagine - after a high speed run, the voice of your mother in your head, telling you that, "If you keep doing that, your face will *stay* that way..."   


-Mark


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## Barbarianjeff (Apr 30, 2011)

Hi Everyone, I am new to the forum, not sure which is the correct thread to use, I am also new to the field of EV's in the truest sense of the word, I am not up on all of the Jargon used or the equipment used. I do however have an EV concept in mind and have done some research. I have a couple of questions for those who feel like answering... 

What is the LOWEST functional voltage that a Warp 9 DC motor can take? *Also, what would the continuous amperage draw be on the Warp 9when maintaining the EV at highway speeds?* if hooked up to 24, 36 or 48 Volt assuming it can operate under such low voltage? I am very restricted to space availability so do not have much room for large battery banks. At this level of development I am more interested to see if my concept will work the way I hope it will rather than looking for mileage range.


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