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Re: (ET) FW: Motor overvoltage
Chris,
You seem to have a pretty good understanding of this works.
I might add, the overvoltage in this case is not the important
consideration the current and related heat buildup is, just like
Chris mentioned.
The added voltage will allow more current which will allow more heat,
just keep an eye on the current levels.
Now, if you wanted to go over 72 volts, then the voltage could become
an issue, as there would be a greater chance of flashover. A timing
adjustment could fix that. But 48v on a 36V motor won't have flashover
concerns, just as Max as shown.
Now, I smoked a 36V motor with 48v on my kids dirt bike. BUT!!! This
was a razor dirt bike, the motor was about HALF the size of an ET
Mower motor. I fully expected to smoke it, just not as quick as I did.
(about 15min).
Original setup was 36v 29A, I upgraded to 48v 100A. He drove it
uphill in the mud. Smoke was coming out by the time he reached the
top. It proved a valuable point though. The original setup couldn't
even go up the hill. This one flew up the hill. Only once though :-) I
bought a bigger motor. Haven't installed it yet though (my life
story).
My sig line is personally sarcastic.
--
Stay Charged!
Hump
The most important substance needed to make a successful project is
the "glue" that makes you stick to it! -- Lee A. Hart
>
>
> -----Original Message-----
> From: elec-trak-bounces cosmos phy tufts edu
> [mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Chris
> Tromley
> Sent: Monday, August 04, 2008 9:11 AM
> To: Elec-trak Mail List
> Subject: Re: (ET) Motor overvoltage
>
> Being an electrical dolt I tend to understand this stuff on the most
> basic level. Maybe I can add some value here, even if only in a
> simplistic sense.
>
> In ICE design you juggle a huge variety of parameters and strike many
> compromises to get as much of the energy in your fuel as possible to the
> ground. An electric motor, however, will do a very good job of
> delivering whatever you feed it. The object of electric motor design
> then is to withstand the power it's managing.
>
> So yes, your 36V motor will certainly handle 48V. The question is how
> long. Will it overheat? Will the brushes and their pigtails handle the
> increased amps? Are the shaft, bearings, etc. up to the increased
> torque?
>
> You may be only looking at a shortening of its life, and probably not by
> much. If it will be used lightly, maybe that doesn't matter. Also keep
> in mind the original 36V rating is probably continuous. How frequently
> will you be giving it the full 48V?
>
> If it was me I'd try it and tread lightly at first. I think there's a
> good chance it will take 48V just fine. If it starts showing signs of
> stress, a supplementary fan might be all you need.
>
> This link to Neon-John's upgrade of a GE Citicar motor might be useful:
>
> http://www.neon-john.com/EV/motor_repair/motor_repair.htm
>
> Chris
>
>
> On Sun, Aug 3, 2008 at 10:23 PM, Max Hall <maxo iname com> wrote:
>
>
> For whatever it's worth, Bill, I drove a 36v golf cart drive
> assembly (motor, diff, axle, oversized wheels, even) at 72v for tens of
> miles (maybe more than 100) in one phase of an EV project. I later used
> the motor for something else... it's still in "circulation' in my
> projects... and it never seemed any the worse for wear. (I think I had a
> 275A max current at 72v, or about 20kW, and I wasn't shy about using it,
> either.)
>
> If that GE motor is really precious to you, a family heirloom
> motor, for instance, don't do it. If you can stand the *possibility* of
> it failing, then I think you should wire it up with confidence; my bet
> is you'll be fine.
>
>
> Confessions of an overdriver,
> -Max
>
>
> On 8/3/08, Bill Alburty <willaim kc rr com> wrote:
>
> I have a 36V Cushman golf car with a GE motor. Does
> anyone know if I can
> increase its speed by increasing the voltage to 42 or 48
> volts without
> damage to the motor?
>
> Thanks,
> Bill Alburty
>
>
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