code to change the motor amp limit

General topics and discussions about the VESC and its development.
rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby rew » 27 May 2017, 07:28

I guess i'm saying KV is inversely proportional to the number of turns. You're saying that resistance is related to the square of the number of turns if you keep the copper volume constant. True. So now KV becomes inversely proportional to the resistance. Call the inverse of the resistance conductance, and you get KV = C(motor) * C(termination) * sqrt(conductance). Sure.

But... does this formula help you in some insight or quick calculations if you make an easy change on your motor?

The formula for the period of a swinging weight is does not include the weight. This leads to the insight that the weight does not matter.

devin
Posts: 255
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby devin » 27 May 2017, 10:58


Hummie
Posts: 110
Joined: 10 May 2016, 04:05
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby Hummie » 27 May 2017, 18:02

I agree that the resistance is proportional to kv. Yes. I haven't disagreed on that. I still don't believe it causes it. Magnetic inductance I believe decides kv/kt (which are inverse). The conversion of turns physically of the wire ,with a core or not, is Linearly related I think into infinity, u can float a frog, and the voltage produced by that field is proportional to the field, and that field and voltage are MORE SO the DETERMINING factor in why the rotor gives out its torque and speed curve of a motor. Is my best basic math hunch.

Wattage passing a core in a wire of any size must have its magnetic field concentrated, overlain, to make a strong enough field to strengthen it. Ideally there would be no back emf that limits speed and people do field-weakening to skirt around the back-emf limit. The weakening of the magnetic field not the changing of the wire resistance is my guess at the method but I don't know how it really works .

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby rew » 28 May 2017, 07:47

OK. Now I get it.

Suppose I have two Y wound motors. One I rewire with thicker wire to make the end-to-end resistance 3x smaller. The second I rewire to delta. You will not be able to measure the difference between the two changed motors. Terminal resistance and KV will be identical.

A useful insight after all! :-)

devin
Posts: 255
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby devin » 28 May 2017, 12:33


rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby rew » 28 May 2017, 13:19

With 1/3rd the copper, you cannot get "identical performance".

Because I think you can substitute thinner wire (but same number of turns) at no damage to the KV, it is easy to create a configuration with the same KV, but less performance. Thinner wire, or "less copper" as you say, will increase the losses.

devin
Posts: 255
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby devin » 28 May 2017, 14:28


rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby rew » 29 May 2017, 06:25

Look you can draw circles and squares all day, but I don't understand what you're getting at.

You claim to have found a relationship between the conductance and the KV. If now you're saying that based on that formula you can make a better motor with less copper, then I'd say that your formula is not correct after all.

I have studied your post a bit better now. Your formula was deduced under the assumption that the copper volume was kept the same. Now you're changing the copper volume and you start getting funny results. The good news: your formula still stands. The bad news: You are using it wrong.

So as to your question: When you reduce the copper volume by a factor of two, and reduce the number of turns, I would say the KV increases. In your example by a factor of sqrt(2).

devin
Posts: 255
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby devin » 29 May 2017, 14:57


rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: code to change the motor amp limit

Postby rew » 29 May 2017, 20:16



[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Return to “General”

Who is online

Users browsing this forum: No registered users and 2 guests