# Calculating torque within a DC MOTOR?

1. Jul 6, 2012

### Momento

The torque that is generated inside a magnetic motor is caused from the magnetic forces that is this formula:

F = ILB

F: Magnetic force(Not sure what the unit would be...)
I: Current(A)
L: Torque(N.m)
B: Magnetic field.( Gauss or Tesla?)

I just need some help in calculating the total magnetic force I know the current & the magnetic field(measured in Tesla or Gauss in this cause?). However, the Torque is confusing for me to calculate... I've looked around and read theses slide countlessly but I really don't know how? I end up scratching my head all night wondering how to calculate the torque!

2. Jul 6, 2012

### Staff: Mentor

Hi Momento. Suggest recheck your textbook (or the web) again to establish what that "L" quantity is.

3. Jul 6, 2012

### 0110alxcpa

My understanding is such that:

F = I l B (sin Θ = 1 )

where F = newtons, I = amps, l = conductor length, and B = magnetic field strength in Tesla.
(remnant field strength may be .7 * max stated value)

You could also use a motor 'constant':

where torque in Nm/A = K * I, and BEMF = Kω

such that K = 2NBLR

where N = # of turns, B = Br*t/(t+g), L = active length (of stator), R = effective radius

where Br = remanent flux density, t = magnet thickness, and g = air gap

4. Jul 6, 2012

### Momento

I'll give it a look.

"(remnant field strength may be .7 * max stated value)"?

All the rest is really confusing... Could you simplify it more and more...?