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  #1561  
Old 03-04-2012, 06:32 PM
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Default Re: Using a forklift motor, and choosing a good one

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Originally Posted by Dan Frederiksen View Post
david, read back and realize I am the righteous one and jrp3 and major attacked me without any reason whatsoever. they should be banned, not me. I'm the one who was really helpful. they didn't help at all.
if you want to be an administrator, be a good one
Enjoy you're vacation, Dan.

Sorry about the thread disruption, guys. If he comes back after 2 weeks and starts trouble again, just let us know and we can make it a permanent ban.
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  #1562  
Old 03-13-2012, 03:53 PM
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Default Re: Using a forklift motor, and choosing a good one

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Originally Posted by zsnemeth View Post
This is looks like some sort of in wheel forklift motor, about 10" diameterand 14 inches long, 36V and has C.E.V. name on it. That's all i could get from the seller.
Doesn't look promising.
Is it useful?

Hi Z,

Yeah, not promising. Not sure about this particular one but looks similar to some US trucks using K H Porter 8 pole short stack motors with gear heads for a wheel motor. It would be difficult to adapt such a motor for an EVcar. I think I'd pass on it unless you have an application for 3 or 4 kW slim motor. And it is likely pretty heavy for its power rating.

Cheers,

major
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  #1563  
Old 03-15-2012, 11:47 AM
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Default Re: Using a forklift motor, and choosing a good one

Hi,

First post here but just looking for some advice on a motor I got for our final year college project.

Would this motor power a Mitisubishi Colt that is completly stripped down and weighing about 700kg.

Thanks for your help
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  #1564  
Old 03-15-2012, 12:44 PM
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Default Re: Using a forklift motor, and choosing a good one

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Originally Posted by DIT View Post
Would this motor power a Mitisubishi Colt that is completly stripped down and weighing about 700kg.
Yes, but at what speed Not very fast. Taking it at nameplate value, it is 0,55kW at 48V, 17A. You can overload electric motors for a short time maybe 3X and raise the voltage increasing RPM and get maybe another 2 to 3 factor which puts you into the 3 to 4 kW range for very short duration unless you actively cool it. So, do you want a car with equivalent performance to that with a 5 hp engine? If you try hard you may come out with an EV which could outrun a golf cart.

Depends on your performance goals,

major
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  #1565  
Old 03-15-2012, 12:48 PM
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Default Re: Using a forklift motor, and choosing a good one

Sorry forgot to say that the car will just be used to be driven around the college parking lot and small distances(.5 of a mile at a time).
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  #1566  
Old 03-19-2012, 09:39 AM
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Default Re: Using a forklift motor, and choosing a good one

major, why do you say that terry's motor is unusable over 100V? that is most certainly wrong. if your thinking is that it can overspeed then that's always a risk with series wound motors in EVs. that's true for all of them. that doesn't make them unusable. it just means you should avoid too high rpm.

you simply don't know what you are talking about.

indeed it is the case that it needs over 100V to reach its full potential in an EV.
a permanent magnet motor has a firm correlation between max rpm and voltage. series wound motors do not.
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  #1567  
Old 03-20-2012, 08:02 AM
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Default Re: Using a forklift motor, and choosing a good one

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Originally Posted by Dan Frederiksen View Post
major, why do you say that terry's motor is unusable over 100V?
Now that we don't have to worry about Dan, I will address this for others who may have wondered.

If you look back over the previous several pages, you'll find that this particular motor has a nameplate rating of 67V and 3200RPM (15 minute). We speculate it is series wound. Regardless, at the rated load, we can proportion the RPM by the ratio of applied voltage. So at 100V, RPM = 4776. This is about as fast as I would recommend; in fact, too fast, I feel for reasonable operating motor speed. Add to that, at any load less than rated, the motor RPM will increase. At current limit (say 400 or 500A), motor RPM would be less than 4776 at 100V applied, but likely still above 4000RPM which would cause commutation arcing. While that might be tolerable for a drag racer, I wouldn't recommend it for the normal EVcar.

I did mention to terryg that the motor could be used with higher voltage battery if the controller could be set to limit the voltage applied to the motor. But I don't see an overall benefit of doing that.

Regards,

major
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  #1568  
Old 03-20-2012, 10:15 AM
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Default Re: Using a forklift motor, and choosing a good one

Hi major
I just start to think I'm getting a grasp on the workings of these motors, then find my mental model is built on shaky ground. Can you help me understand your reasoning? I can see that this particular motor is not very suitable with its low 15-minute current rating, but I'm not sure I follow the voltage limit reasoning. I got the impression that the nameplate rating was just one datum point, often chosen for the benefit of the intended customer. The current limit is obviously fixed by the efficiency of the motor and its ability to dissipate heat. But aren't most series motors run well beyond what would originally have been their nameplate voltage?

I can see that raising the voltage considerably or reducing the load/current outside the nameplate values will cause the motor to speed up, and that this can result in excessive arcing or the commutator flying apart. But in a decent conversion the upper rpm should be limited by gearing or the controller, or by using a separate rpm limiter. Is it just that this motor looks particularly weak, or do you feel that many of us are pushing motors too far outside their safe working envelope? In my case I'm thinking of running a 36V/2500 rpm rated Prestolite motor at up to 120V, though I have advanced the timing several degrees to try to counter arcing.
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  #1569  
Old 03-20-2012, 11:39 AM
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Default Re: Using a forklift motor, and choosing a good one

Hi Malc,

I'll give it a try

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Originally Posted by MalcolmB View Post
I can see that this particular motor is not very suitable with its low 15-minute current rating,..
Well, it depends on the intended application. It was rated at 15 minutes because it was designed for a pump drive and a 15 minute rating was considered more of a typical load for that application. It does not imply that this motor cannot be run longer at a lower load. In fact many (or some) motor performance graphs include a time vs load curve indicating how long the motor can be run at a particular load. This motor, as I mentioned in post #1661 may carry a 2 or 3 kW rating for one hour. Now that may be suitable for a small, or low speed car, or MC.

Quote:
Originally Posted by MalcolmB View Post
But aren't most series motors run well beyond what would originally have been their nameplate voltage?
No. I'd say most motors are used in the intended application reflected by the nameplate. It is us idiots doing EV conversions who choose to use motors in non-intended applications with operating parameters disregarding nameplates.

Quote:
Originally Posted by MalcolmB View Post
I can see that raising the voltage considerably or reducing the load/current outside the nameplate values will cause the motor to speed up, and that this can result in excessive arcing or the commutator flying apart. But in a decent conversion the upper rpm should be limited by gearing or the controller, or by using a separate rpm limiter.
I don't follow you about gearing, but regarding the controller and RPM limiter.....That reduces voltage to the motor. Exactly what I was talking about. 100V to that motor will result in excessive RPM at reasonable loads. You can have a higher voltage battery, but you must keep the motor voltage lower. And the RPM limiter is just a circuit which uses the motor controller to limit the motor voltage.

Quote:
Originally Posted by MalcolmB View Post
Is it just that this motor looks particularly weak, or do you feel that many of us are pushing motors too far outside their safe working envelope? In my case I'm thinking of running a 36V/2500 rpm rated Prestolite motor at up to 120V, though I have advanced the timing several degrees to try to counter arcing.
That motor looked just fine for what it is. I covered some aspects which might present some difficulty for him. As far as your motor, I think that 36V/2500 RPM point would be about the rating (1 hr) at around 200A. If you apply 120V volts to the motor with a 200 amp load, it will attempt to run at 8300 RPM.

Regards,

major
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  #1570  
Old 03-20-2012, 12:10 PM
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Default Re: Using a forklift motor, and choosing a good one

Quote:
Originally Posted by major View Post
It is us idiots doing EV conversions who choose to use motors in non-intended applications with operating parameters disregarding nameplates.
major
Yes, I meant "most series motors used by us idiots"

Quote:
Originally Posted by major View Post
I don't follow you about gearing
I was thinking of a fixed gear conversion where the motor rpm is limited by by the achievable top speed.

Quote:
Originally Posted by major View Post
You can have a higher voltage battery, but you must keep the motor voltage lower. And the RPM limiter is just a circuit which uses the motor controller to limit the motor voltage.
Doh, newbie mistake, that's where I was tripping up, thinking you were talking about pack voltage rather than motor voltage.

Thanks for taking the time!

Malcolm
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