TORQUE CHARACTERISTICS OF DIRECT CURRENT MOTORS.

The torque developed by a motor:

The tendence of a motor to produce rotation, depends upon two factors:

a).- The flux created by the main poles   and:

b).-The current flowing in the armature winding

Therefore, the torque is independent of speed of rotation.

This statement can be wiritten in equation 1 form thus:

    T= (k)(FM)(IA))  in lb-ft   equation 1

Where:

T  = Torque  (usually in pound-feet)

FM= Flux per pole in Maxwells

IA  = Total armature current

K = Proporcionality constant (to be determined in the following equations.
Z =  Total number of armature conductors.

To derive Eq. 1 the following analysis is given:

the power developed by motor is:

Pd  =( EC )(IA)   in watts        Equation 16

but we may know,

  Ec = (FM)(P)(Z)(rpm)/ (a)(60)(10exp 8),   Equation 17

Therefore:

Equatin two equations 16 and 17 respectibely,

we will have:

Pd =[ [(FM)(P)(Z)(rpm)/(a)(60)(10exp 8)](IA)]]

Also   we have knowledge that 

 1hp= (2)(3.416)(rpm)(T)/ 33000

Where T is the torque in pound-feet and 

1 hp = 746 watts

if equating the two values of Pd    we will be:

[[(FM)(P)(Z)(rpm)/(a)(60)(10exp8)](IA)=[(2)(3.1416)(rpm)(T)/(33000)][(746)]]

Then:

T =[ (33 000/(2)(3.1416)(60)(746)(10exp8)(FM)(P)(Z)/a](IA)

This is equal:

[(0.1173/10exp8 )][(P)x(Z)/a)]x (FM) x (IA)]   in lb-ft 





Note: you can to apply this formule, and you will can see  and tray, that; this is very usefull in  many solutions to severals problems about  of direct current motors world. 
ok ?    

Good look in your aplications, in reality professional Job.

I will be very thankeful if you can  comment about this topic, that I wrote for you. I hope  to recibe some soon.

"Is good to know, but is better you can apply a little of the knowledge, or not ?"
 This is my personnal thinking  away.

Sincerily   Eng. Miguel Ismerio Espinosa