# motor tested



## evz (Sep 11, 2008)

after cleaning my 200lb forklift motor
i had it tested 
it was originally intended for 36-48v

without advancing the brushes we went as high as 72volts with no problems
@ 3000 rpm
no arcing of the brushes

the testing unit was maxed out at 30 amps and thats as high as we could go 

ill need to find someone with a bigger tester ( vari-amp ) 

id like to know how many volts it will take to turn the motor @ 4500 rpm


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## major (Apr 4, 2008)

evz said:


> after cleaning my 200lb forklift motor
> i had it tested
> it was originally intended for 36-48v
> 
> ...


Hey evz,

I looked back at your earlier post. This is the big motor of those 3, right? I guess I would have expected a higher speed at no load. 30 amps doesn't sound too bad. But a series motor, I would have thought to spin 2 to 3000 RPM at no load with like 12 volts. And you put 72 on it? Motor designs vary; I have no idea what you really have there, but sounds fishy to me.

As far as 4500 RPM goes, that might be about as high as you would want to go. And, from theory, RPM is proportional to volts. But, I'd hate to see you put high voltage on that big motor and a bearing get loose or something where it over speeds. There will be lots of copper bullets flying all over the place.

I haven't seen much of Jim Husted lately. Halloween is always his busy season. But try to get his opinion.

Regards,

major


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## kugmo (Oct 31, 2008)

hmm, interested in it, so how did this go?? I hope it faired well.


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## kek_63 (Apr 20, 2008)

If that is a series motor make sure you have a load on it when you put higher voltage to it. You may very well "test" it into pieces! I think you were fortunate that your power supply didn't have more juice. Normally 72v into an unloaded series motor will result in a very quick overspeed/damage situation. Bench test with 12v only.

Later,
Keith


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## evz (Sep 11, 2008)

i assume the electrical shop did put a load 
cause at 72 volts it only reved at 3000 rpm

in any case this is a big motor with a large diametre 
, a lot of torque i bet ,
probably doesnt need to rev very high 

without advancing the brushes looks like i could build a 72v system, 

at 3000 rpm in forth gear i should be able to drive freeway speeds

something to think about


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## evz (Sep 11, 2008)

ok so can i assume , under load , in a functioning ev , 
, that if i double my voltage , i can double my rpm ?

if a motor does 3000 rpm at 72 v , 

@ 108 v , could i expect to reach 4500 rpm on the freeway ?


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## kek_63 (Apr 20, 2008)

You're on the right track. But you have to take the efficiency of the motor and the aerodynamics of the vehicle into account; so top speed would be less than 1.5x.


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## evz (Sep 11, 2008)

i went to pick up my two forklift motors and asked a few more questions,
as it turns out we didnt have a load on the motors afterall .
the technician simply cut the power before the higher voltage over reved the motor .
we're probably lucky we didnt damage anything .

but they re nice and clean anyways ,

also advancing the brushes on the bigger 200lbs traction motor is more problematic because of its design ,
ill have to settle for 72-96 v, 
or whatever the motor can handle with brushes as they are .

the smaller lift motor of 100 lbs would be easy to advance 10°


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