code to change the motor amp limit

General topics and discussions about the VESC and its development.
Hummie
Posts: 109
Joined: 10 May 2016, 04:05

code to change the motor amp limit

Postby Hummie » 07 May 2017, 17:50

Anyone have it and could give a super simple explanation for the non-knowing of how to change it?

Anyone have a simple detailed explanation of the risks?

rew
Posts: 940
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: code to change the motor amp limit

Postby rew » 07 May 2017, 19:43

you should use BLDC tool to configure the motor amp limit.

Or are you asking how you can do 20A into a 10A motor? Just configure it using BLDC tool.

Motors do not die from too much current. They die when they get too hot. So if you only use the high current for short timespans, then it might be possible to keep the motor in one piece with a current setting much higher than what the manufacturer specified.

hexakopter
Posts: 86
Joined: 24 Dec 2015, 15:24
Location: Germany

Re: code to change the motor amp limit

Postby hexakopter » 07 May 2017, 22:08

I think he is asking again what he already has asked on this forum (here: http://vedder.se/forums/viewtopic.php?f=6&t=643 ; here: http://vedder.se/forums/viewtopic.php?f=6&t=6&p=3712#p3712 ; here: http://vedder.se/forums/viewtopic.php?f=6&t=371 ; etc.) and even more often on the electric-skateboard forum and has got the questions answered multiple times.
I think he wants to know how to set the BLDC-Tool limit higher than 200A and what consequences that would have. I answered him these questions already on the electric-skateboard forum.
I told him he is not hitting 200A motor amps in my opinion and that he should record his run to see that. He told me he will do that, but that was over 4 month ago, I think.

But nice to see that you don't get tired to answer him again and again, rew. :)

Hummie
Posts: 109
Joined: 10 May 2016, 04:05

Re: code to change the motor amp limit

Postby Hummie » 07 May 2017, 22:26

so that's the answer. the sensor can't sense that high? that's as good an answer you can come up with. instead of trying to belittle me how bout you have a decent answer. I rode many miles at 200 motor amps and am asking why it works and works well when it's said the sensor can't do it.
no i still haven't been logging. But I dont know how these things work and should I infer under a big enough load at full throttle the amount of motor amps I would hit would be different?

actually rew I didnt see what you wrote above and just this guy but it still stands. you're a great help but I'm not hearing what i want to hear :twisted: there's a guy on the skate forum and he's limited to 6s with the vesc-x and wondering what settings will give more power and smoothness. here are his options for continuous power at all rpms, but if he wanted to increase his power at the slowest speed he has to increase the motor amp setting even higher.


360 watts
13 battery amps
160 motor amps and max max of 200

478 watts
20 battery amps
200 motor amps max max of 200

for me doing 200 motor amps it rode as good as ever. I could start from stop. no cogging, less noise, smoother. makes me look for a better reason I shouldn't be doing it or why i didnt break the vesc
Last edited by Hummie on 07 May 2017, 22:56, edited 1 time in total.

hexakopter
Posts: 86
Joined: 24 Dec 2015, 15:24
Location: Germany

Re: code to change the motor amp limit

Postby hexakopter » 07 May 2017, 22:55

Because I think you don't changed the shunts to different ones (from 1mOhm to 0.5mOhm), yes you can't sense that high.
I don't belittle you, I am just tired to answer you the same thing aging and again.

I think you don't get the point that you didn't rode many miles at 200motor amps, but rode many miles with the motor max amps set to 200A without hitting 200A motor amps. When you don't exceed the "max possible hardware sensed" motor amps (around 160A) in your actual run (remember you rode many miles with the motor max amps set to 200A without hitting 200A motor amps) it works well when it's said the sensor can't do it.

When you don't know how to buy a BT module, set it up and connect it to the VESC UART port, just go here https://metr.at/shop and buy that module. It just needs to be plugged into the right port and thats it. Idiotproof.

When I got your last sentence right, yes you should infer that.

Hummie
Posts: 109
Joined: 10 May 2016, 04:05

Re: code to change the motor amp limit

Postby Hummie » 07 May 2017, 23:01

youre saying the current to the motor would be controlled by the load and not the throttle. I thought current control was current control and when I pull the trigger all the way I have access to whatever current the settings allow based on the duty cycle.

i have a little plug chip for my vesc and an app on my phone right now. i just dont bother for some reason.

hexakopter
Posts: 86
Joined: 24 Dec 2015, 15:24
Location: Germany

Re: code to change the motor amp limit

Postby hexakopter » 07 May 2017, 23:28

Maybe you need an evidence to believe me. In the picture you can see an extract from one of my logs. My max motor current was set to 150A my max battery current to 50A. Do you see me hitting 150A motor amps? I used full throttle.
Attachments
metr.at log.png
metr.at log.png (402.85 KiB) Viewed 5339 times

devin
Posts: 253
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US

Re: code to change the motor amp limit

Postby devin » 08 May 2017, 02:45

this graph seems odd in that the last 3 "power pulses" have correlated shapes between the 2 red lines, but the first 3 "power pulses" lose the correlation and appear to be "capped" or flatlined at some arbitrary value.

hexakopter
Posts: 86
Joined: 24 Dec 2015, 15:24
Location: Germany

Re: code to change the motor amp limit

Postby hexakopter » 08 May 2017, 05:53

That is not odd at all. The "red lines" (also known as motor current and battery current) have correlated shapes when the duty cycle is near at its max value of 95%.

The value where to battery current is "capped" is not an arbitrary value. Its the 50A max battery current that I have set in BLDC tool.

devin
Posts: 253
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US

Re: code to change the motor amp limit

Postby devin » 08 May 2017, 06:41

in the case of the use of 200 motor amps,

-the single hub motor had 0.0415ohm windings
-battery was assumed ~35v nominal under load
-desired available wattage electrical at all possible rpms was 1660 watts
-settings used were 48/200/200 batt/motor/absolute max

48 batt amps x 35v pack volts = 1680w

200 motor amps x 0.0415 ohm resistance = 8.3 pwm effective volts

8.3 pwm effective volts x 200 amps = 1660 watts

(8.3 pwm effective volts / 35 pack volts) x 100 = ~23.7 duty cycle @ full throttle standstill

in simple terms 200 motor amps & 48 battery amps would have been reached in the event of full throttle standstill.

(less than 200 motor amps possible above ~0rpm)

i witnessed hummie ride around san francisco for as i recall at least a week on these settings.

if he didn't press the throttle fully with the board loaded close to 0rpm it's possible he didn't reach 200 "motor amps".

Image

Image

Image

video:

http://youtu.be/Eqm6NWf6r7Y


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