Search found 253 matches

by devin
24 Mar 2018, 09:46
Forum: General
Topic: would this method be accurate to determine a motor winding resistance?
Replies: 3
Views: 386

Re: would this method be accurate to determine a motor winding resistance?

Is this accurate? In the sense of "is this theoretically correct" the answer is: Yes. (albeit that your result includes the resistance of the VESC and maybe also the battery wires). In the sense of: will the result be the same (similar) in different cases? The answer is: no. i believe Mr....
by devin
24 Mar 2018, 09:36
Forum: General
Topic: General questions
Replies: 12
Views: 1448

Re: General questions

Suppose the rider is coasting at 10mph (below no load speed) at 0% throttle...

while coasting at 0% throttle, is the vesc applying a pwm effective voltage which is equal to the back emf voltage at all times or are all the mosfets “off”?
by devin
22 Mar 2018, 16:46
Forum: General
Topic: General questions
Replies: 12
Views: 1448

Re: General questions

my understanding is the back emf voltage at this speed will exceed the battery voltage.\ When the voltage from the motor exceeds the battery voltage, the parasitic diodes in the mosfets will function as a three-phase-rectifier. Thus even without using the throttle, the motor will start working as a...
by devin
13 Mar 2018, 13:03
Forum: General
Topic: Low speed high torque
Replies: 3
Views: 538

Re: Low speed high torque

because many folks have been confused previously about the difference between battery amps and motor amps-- to illustrate, here are 2 charts I made for comparing the theoretical performance of 50a battery amps vs 50a motor amps: *please make sure you do not exceed the amp limits of any of the hardwa...
by devin
13 Mar 2018, 12:26
Forum: General
Topic: Low speed high torque
Replies: 3
Views: 538

Re: Low speed high torque

have you tried increasing the motor amp limit as torque is directly proportional to motor amps. if you double the motor amp limit you double the torque limit. a friend of mine solved his low speed torque startup issues by using the (some would say extreme method) of boosting the motor amp limit (in ...
by devin
11 Mar 2018, 16:24
Forum: General
Topic: General questions
Replies: 12
Views: 1448

Re: General questions

Dor, please ignore Devin. He's got some non-scientific ways to get some results that are not scientifically valid. He starts out with assuming a gear ratio. That's the last thing you need. The motor can put out 2500 Watts. If we take that to be correct, the main question is: Can you do 15mph on 250...
by devin
11 Mar 2018, 15:01
Forum: General
Topic: would this method be accurate to determine a motor winding resistance?
Replies: 3
Views: 386

Re: would this method be accurate to determine a motor winding resistance?

Second Example: This is a still frame from Benjamin Vedder's electric skateboard logging video: http://tppsf.com/27a-41w-1.jpg Speed (mph): 0mph Battery Amps: 1.26a Motor Amps: 27.33a <---------- Battery Voltage: 33.2v Back EMF Voltage: 0v <---------- Electrical Watts: 41.8w <---------- Since Back E...
by devin
11 Mar 2018, 14:48
Forum: General
Topic: would this method be accurate to determine a motor winding resistance?
Replies: 3
Views: 386

would this method be accurate to determine a motor winding resistance?

Hello, Does anybody know if this method for determining a motor's winding resistance from data logging videos will give accurate results? Thanks, Devin ---------- Example 1: http://tppsf.com/accelleration-1.jpg From this screenshot of a data log I want to determine the resistance in ohms from lead t...
by devin
05 Mar 2018, 17:11
Forum: General
Topic: General questions
Replies: 12
Views: 1448

Re: General questions

i made a comparison chart of 1 motor set to 57a max motors amps as previously described [24v battery, 0.05ohm winding, 1.5:1 gear reduction, 90mm tire, 190kv], and 4 identical motors set to 14.25a max motor amps. in theory the riding performance should be almost indistinguishable, but with 4 motors ...
by devin
04 Mar 2018, 14:52
Forum: General
Topic: General questions
Replies: 12
Views: 1448

Re: General questions

& as rew says, if you change the assumptions I chose from 3:1 to 2:1 gear reduction, then by my calculations and factoring the wind you can reach somewhere between 20-25 mph (32.1-40.2kph) before the wind drag force exceeds the thrust force from looking at the middle, top row chart. http://tppsf...

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