Advanced DC K91-4003 max voltage

Electric Motors and Controllers
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elon'sMusk
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Advanced DC K91-4003 max voltage

Post by elon'sMusk » Apr 13, 2018 11:34 am

Hi all, I'm new to this forum. I'm building an electric go kart and I have picked up a series wound Advanced DC Motor rated between 72 and 96V.

It is rated 6kW 16.5 kW peak at 72 volts and 7.3 kW 21.3 kW peak at 96V. The LiFePo4 batteries I am using come in 12S packs, so I would like to use 3 of them in series at 36S total, or 115.V

From your guy's experience, do you think I will blow out the brushes/commutator or destroy windings with this amount of overvoltage? I would like to go insanely fast, but it would really suck to lose my motor.

major
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Re: Advanced DC K91-4003 max voltage

Post by major » Apr 13, 2018 10:25 pm

I doubt that the voltage you state will be a problem. Your controller will limit the voltage to the motor. So what you need to do is figure a way to observe the brush/commutator area as you accelerate, keeping the RPM within limits. If it starts arcing badly then you'll need to advance the brush position.

Be aware that the series wound motor at no load with voltage applied will overspend to destruction in a heartbeat. Karts typically use chain drive prone to coming off the sprocket. You need either a motor speed sensor and controller shutdown circuit or a flakjacket.

Speaking of it, what controller are you using?

Regards,

major

Punx0r
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Re: Advanced DC K91-4003 max voltage

Post by Punx0r » Apr 14, 2018 5:01 am

Depending on how stiff your LiFePO4 pack is and how hard you lean on it you may find the voltage sags below the 115V nominal, so when you're giving it the beans you may not actually be that far above the motor's 96V rating.

Brushed motors seems to work fairly well in drag racing where they are run at currents waaaaaaaaaay over their rating. As long as you're prepared to tolerate increased brush wear (bearing in mind in normal use they should last years) you ought to be able to turn up the wick a bit.

elon'sMusk
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Re: Advanced DC K91-4003 max voltage

Post by elon'sMusk » Apr 14, 2018 5:51 pm

major wrote:
Apr 13, 2018 10:25 pm
I doubt that the voltage you state will be a problem. Your controller will limit the voltage to the motor. So what you need to do is figure a way to observe the brush/commutator area as you accelerate, keeping the RPM within limits. If it starts arcing badly then you'll need to advance the brush position.

Be aware that the series wound motor at no load with voltage applied will overspend to destruction in a heartbeat. Karts typically use chain drive prone to coming off the sprocket. You need either a motor speed sensor and controller shutdown circuit or a flakjacket.

Speaking of it, what controller are you using?

Regards,

major
Thanks for your guys replies. I was originally going to use a 72V Curtis 1209 knockoff, but I wanted more voltage and I found a controller on ebay rated 200V 300A peak, 200A continuous. I think this should be enough to feed the motor, but I would really like the Open ReVolt 500 amp controller. However all of the information on it appears to be gone and I don't know where to get a control board for it.

https://www.ebay.com/itm/300A-200V-72V- ... SwGJlZHd00

major
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Re: Advanced DC K91-4003 max voltage

Post by major » Apr 14, 2018 7:38 pm

For the open revolt look for Sabrina Holmes on Evtech discussion list, http://lists.nnytech.net/listinfo/evtech

Also occasional poster on diyelectriccar forum. Taking more of a risk with eBay IMO. I think tech support has been there for open revolt builders.

You'll like 500A way more than 300.

Good luck,

major

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liveforphysics
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Re: Advanced DC K91-4003 max voltage

Post by liveforphysics » Apr 14, 2018 7:46 pm

I ran 232vdc and 1,000amps into my ADC 8" motor in my sparrow.

It really hated 1,000amps and would randomly eject blasts of molten copper, but made good torque and kept running somehow.

In really dry weather, it would handle it pretty well, and in humid conditions or if I ever got the motor wet from driving through a puddle or whatever, it would arc-fault terribly even at a few hundred amps.
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