# PMG132 or AGNI Motor?



## frodus (Apr 12, 2008)

PM or Email jozzer on endless-sphere
http://www.endless-sphere.com/forums/index.php

and join Elmoto.net there's lots of us EM guys there.

It comes down to cost... the agni is more expensive.

Another guy to talk to is Andy on evmotorcycle.org


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## Georgia Tech (Dec 5, 2008)

You asked about the PMG132 reliabilty???
Well please take a look at this sight and this guy who used it in a real application.....I better not comment because DIYguy will have a hissy and say I don't know what I am talking about....
Here: http://www.neurotikart.com/
scroll down to , 23 August 2007 on this sight he can tell you what he exprianced....


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## flashedarling (Jun 30, 2008)

I have read about how it will crap out on you very quickly if you run it at 72v in the wrong direction. Also that that Perm doesn't make it clear that it is supposed to run CW at that voltage or you will fry it. Other than that I haven't anything to go on. 

Although I hear the Agni is more expensive I have no clue where to buy it from. Do I have to order it from the manufacturer in India or is there someone in the US I could buy one from?


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## Georgia Tech (Dec 5, 2008)

flashedarling said:


> I have read about how it will crap out on you very quickly if you run it at 72v in the wrong direction. Also that that Perm doesn't make it clear that it is supposed to run CW at that voltage or you will fry it. Other than that I haven't anything to go on.
> 
> Although I hear the Agni is more expensive I have no clue where to buy it from. Do I have to order it from the manufacturer in India or is there someone in the US I could buy one from?


Have you alreay invested money in either of these?
I at one point was set bent on using a Permanet Magnet motor. But in doing my study of the construction of these things I could not birng my self to use one. Although I think these perm motors are 8 pole motors I was looking at 4 pole motors. I was looking at Leeson the hardest, Ohio, and Scott. I never looked closely at these pancake motors that much. I heard from someone else that there perm motor did not hold up to well either. I did here some good things about the mars motors though. Could EV sells them. It REALLY seems as if these PM motors do not hold up well to large amounts of current as well as a field wound motors. But how ever your application is not a performance application you stated that you wanted to cruise around 40 to 50 MPH. I think you could be OK. I can see why a pancake magnet motor is desirable for a bike.


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## Georgia Tech (Dec 5, 2008)

A while back I talked with an engineer from Leeson about there Permanent magnet motors it was later I told them the application. But anyway, I asked them having a 24 volt motor that made 4 hp at 1800 rpm. They said it was physically impossible for them to make such a motor. They explained they could not get enough magnetics or active material to produce such a beats and get this that the torque would somehow produce too much heat!! I don't quite understand how torque and heat was related in this fashion. Any way it got down to "what’s the application?" and told him a very small EV (gokart). He then drop the whole conversation and said go with a field wound motor, I mean it was almost no discussion. From what it seems large amounts of Torque and magnetic flux due to big currents has a negative residual effect on permanent magnets. But like I said your doing more of a cruise and not a lot of hot dogging. I think you will be quit OK. Beside Per motors do have regen!!


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## Georgia Tech (Dec 5, 2008)

flashedarling said:


> I have read about how it will crap out on you very quickly if you run it at 72v in the wrong direction.


Well they must be useing some sort of angled brush design of some sort. You would think one advantagous reason for using a Permanent magnet motor is to be able to run it in reverse.


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## Kirk_Wallace (Nov 20, 2008)

I am very new to EV motors, so I hope no one minds me putting my two cents in. My take on permanent magnets is that in order to make something magnetic, you have to align the electrons (or electron spins) of the material in one direction. To do this you need to get the material in a state where the electrons are loosely held and expose the material to a magnetic field, then fix the electrons by bringing the material to a normal state. Heat and very strong magnetic fields seem to be the methods for setting up magnetism in materials, which also is what the magnets are exposed to in a motor application. If you stress the motor enough, you can produce enough heat or field to de- or re-magnetize the magnets. Stretch or heat a spring enough and you get a very different looking spring afterwards. Some of these materials are so sensitive, such as in stepper motors and magnetos that just disassembling the unit can demagnetize the magnets. For an EV motor, especially in a DIY project where the unexpected often happens, permanent magnets may not be the best choice. You still need to worry about over stressing a wound field motor, but recovering from a transgression, I think might be easier and cheaper with copper rather than neodymium.

As far as brush advancement, I was hoping to find information on this list about it, but my guess so far is, it might be similar to engine spark advance, where you try to adjust the spark timing to extract the most mechanical advantage from each combustion event. For the most part each combustion event takes about the same to complete, but the mechanical geometry of the piston, rod and crank changes dramatically with RPM. For higher RPM, the combustion needs to start earlier so that the combustion "sweet spot" will match the much shorter mechanical "sweet spot". I think EV motors may have a similar problem. I think for a motor, the mechanical geometry (the armature pole center of magnetism in relation to stator pole center) and the field dynamics (field strength changes relative to voltage, current and time) need to be adjusted over the RPM range. For a motor with a fixed (static) brush holder I think the advance is a compromise based on the application. If the motor application needs to rotate in both directions, I think a further compromise puts the field centers half way between each other, so that the motor behaves the same in both directions, and degrades as RPM increases.

For the Perm motor mentioned above, there may be design compromises that where made to cater to an application that degrades performance more in one direction. I would guess that ideally, one would want a mechanical or electronic advance that adjusted for direction, voltage, current, RPM, temperature or whatever else changes the field dynamics. This may be what EV AC induction motor controllers do.

Hopefully, those with experience, can correct the guess work I presented.
-----------
Kirk
http://www.wallacecompany.com/machine_shop/


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## Georgia Tech (Dec 5, 2008)

Kirk_Wallace said:


> I am very new to EV motors, so I hope no one minds me putting my two cents in. My take on permanent magnets is that in order to make something magnetic, you have to align the electrons (or electron spins) of the material in one direction. To do this you need to get the material in a state where the electrons are loosely held and expose the material to a magnetic field, then fix the electrons by bringing the material to a normal state. Heat and very strong magnetic fields seem to be the methods for setting up magnetism in materials, which also is what the magnets are exposed to in a motor application. If you stress the motor enough, you can produce enough heat or field to de- or re-magnetize the magnets. Stretch or heat a spring enough and you get a very different looking spring afterwards. Some of these materials are so sensitive, such as in stepper motors and magnetos that just disassembling the unit can demagnetize the magnets. For an EV motor, especially in a DIY project where the unexpected often happens, permanent magnets may not be the best choice. You still need to worry about over stressing a wound field motor, but recovering from a transgression, I think might be easier and cheaper with copper rather than neodymium.
> 
> For the Perm motor mentioned above, there may be design compromises that where made to cater to an application that degrades performance more in one direction. I would guess that ideally, one would want a mechanical or electronic advance that adjusted for direction, voltage, current, RPM, temperature or whatever else changes the field dynamics. This may be what EV AC induction motor controllers do.
> 
> ...


 

Very nice post Wallace!! and VERY true too!!


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## Georgia Tech (Dec 5, 2008)

Oh and welcome abore Kirk wallace!


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## Dtek (Jul 5, 2009)

Kirk, you are correct.
We used to have rules in our RC racing classes as to what constituted a 'stock class motor'. the main issue (besides it having to be a bushed motor) was brush 'timing'. the same mild, long life motor with 5degrees timing became a much more formidable powerplantwith 25-27 degrees...and a downright screamer at 40degrees. 
Of course Battery life , brush life and commutator life all suffered greatly.

There are some web videos of the Quantya ( I believe its powered by a Lemco motor) dirtbike that show it with a hop-up kit. a small handlebar mounted lever is cable connected to a rotating brush housing... squeeze for more top end 'over-run'.


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## BradQuick (May 10, 2008)

I have a Perm motor in my motorcycle. Unfortunately, I've had problems with it. The first problem was that it wasn't built right at the factory and the stator rubbed on the magnets. After I shimmed it out, it ran for a few months, but then I had some arcing in the motor. I think a winding shorted out. I emailed the company and they say that they have sent me a new rotor. I hope to get it any day now. 

I believe the AGNI motor is a better, but more expensive motor, but I don't have any experience with it. 

If I had to do it again, I would probably get an Etek-RT motor for less money.

- Brad


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## Jozzer (Mar 29, 2009)

Agni should be cheaper than the Perm (£745), and way outperforms it. Being much more efficient it can take a lot more power before it gets hot. The Etek RT (Mars) is way cheaper, but only good for about half the power and almost twice as heavy. Both the Mars and Perm will overheat if you throw more than 100A at them for very long, the Agni will take 220A contin and 400A peak, and the reinforced 95 series will take it all the way to 6000rpm!
Steve


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## penguinapricot (Apr 19, 2010)

In the olden days permanent magnets were weak,
More recently (10 years) 'rare earth magnets' have become cheaper making permanent magnet motors much more powerful.

With coils on the stator, with magnets on the rotor.
Because the coils are on the outside, the heat can be taken away more readily.
The heat is due to the current in the coils: Watts heat = Current^2 * resistance.

Watts in = Voltage X Current.





Georgia Tech said:


> A while back I talked with an engineer from Leeson about there Permanent magnet motors it was later I told them the application. But anyway, I asked them having a 24 volt motor that made 4 hp at 1800 rpm. They said it was physically impossible for them to make such a motor. They explained they could not get enough magnetics or active material to produce such a beats and get this that the torque would somehow produce too much heat!! I don't quite understand how torque and heat was related in this fashion. Any way it got down to "what’s the application?" and told him a very small EV (gokart). He then drop the whole conversation and said go with a field wound motor, I mean it was almost no discussion. From what it seems large amounts of Torque and magnetic flux due to big currents has a negative residual effect on permanent magnets. But like I said your doing more of a cruise and not a lot of hot dogging. I think you will be quit OK. Beside Per motors do have regen!!


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