- #1

Jonathan

- 365

- 0

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter Jonathan
- Start date

- #1

Jonathan

- 365

- 0

- #2

L = - (dI/dt)*(1/Us)

where dI/dt is speed of current variation (dI is current variation, dt is time of variation), and Us is sefinductivity voltage.

- #3

Jonathan

- 365

- 0

- #4

oi couldn't figure the easier way for determining selfinductivity if you already have em. coil, so here it is :

we need basic three values about coil, it's current, voltage, and resistance. i believe you already know voltage, so you can measure the resistance of coil with normal ohmmeter, and then get current with I = U / R.

we need to know number of turns too. use the formula R = ro * (l/S), where ro is specific resistance (you can find those values on the internet for every material, for copper is 0,0175), l is length of wire and s is surface (in mm2). then you can use simple geometry to determine number of turns. you need to know the~~ surface value for that. N = lair / 2*sqrt(S/3.14). lair is length of coil, not of wire, and you can use normal meter to measure it.~~

in my previous post i gave that formula. Us is selfinductivity, and L is inductivity. Us is voltage that appears when magnetic flux changes inside the coil as direct effect of current change trough coil. so we need to know inductivity to determine selfinductivity.

Us = -L*(dI/dt)

inductivity : L = N^2 / Rm . we already calculated number of turns so onlything that's left is Rm, the electromagnetic resistance.

Rm = theta / fi

theta = I * N , the magnetomotoric force. we have both of values required, the current trough coil and number of turns

fi = B * S, the magnetic flux. note that S here isn't same as surface of the wire, it's the surface of electromagnetic pole. you can determine it by measuring the radius of the coil, and then using r^2*pi.

B = [mi-zero]*[mi-relative]*(I*N)/l , the field strenght. [mi-zero] is permeability of free space constant, and it equals 1,257e-6 (0,000001257). [mi-relative] is permeability of core. if your coil doesn't have iron or other core beneath it, then youre using air coil, and [mi-relative] is 1. for other materials refer to this URL : http://www.oz.net/~coilgun/theory/materials.htm. [Broken]

we need basic three values about coil, it's current, voltage, and resistance. i believe you already know voltage, so you can measure the resistance of coil with normal ohmmeter, and then get current with I = U / R.

we need to know number of turns too. use the formula R = ro * (l/S), where ro is specific resistance (you can find those values on the internet for every material, for copper is 0,0175), l is length of wire and s is surface (in mm2). then you can use simple geometry to determine number of turns. you need to know the

in my previous post i gave that formula. Us is selfinductivity, and L is inductivity. Us is voltage that appears when magnetic flux changes inside the coil as direct effect of current change trough coil. so we need to know inductivity to determine selfinductivity.

Us = -L*(dI/dt)

inductivity : L = N^2 / Rm . we already calculated number of turns so onlything that's left is Rm, the electromagnetic resistance.

Rm = theta / fi

theta = I * N , the magnetomotoric force. we have both of values required, the current trough coil and number of turns

fi = B * S, the magnetic flux. note that S here isn't same as surface of the wire, it's the surface of electromagnetic pole. you can determine it by measuring the radius of the coil, and then using r^2*pi.

B = [mi-zero]*[mi-relative]*(I*N)/l , the field strenght. [mi-zero] is permeability of free space constant, and it equals 1,257e-6 (0,000001257). [mi-relative] is permeability of core. if your coil doesn't have iron or other core beneath it, then youre using air coil, and [mi-relative] is 1. for other materials refer to this URL : http://www.oz.net/~coilgun/theory/materials.htm. [Broken]

Last edited by a moderator:

- #5

Jonathan

- 365

- 0

- #6

- #7

Jonathan

- 365

- 0

I don't yet have a particular system in mind. When I do, I will PM you, thanks.

Share:

- Replies
- 10

- Views
- 2K

- Replies
- 13

- Views
- 373

- Last Post

- Replies
- 15

- Views
- 1K

- Replies
- 26

- Views
- 1K

- Last Post

- Replies
- 4

- Views
- 410

- Replies
- 11

- Views
- 466

- Last Post

- Replies
- 5

- Views
- 2K

- Last Post

- Replies
- 14

- Views
- 2K

- Replies
- 9

- Views
- 3K

- Replies
- 17

- Views
- 1K