Motor Torque Equation Question

  • #1

Main Question or Discussion Point

The torque equation for a DC motor is: T = (P.Z.φ.I)/(2.π.A)

Where:
P = no. of poles
Z = no. of winding conductors
φ = flux per pole
I = current
A = no. of winding parallel paths

My question concerns the "parallel paths". What are "parallel paths"? Why do they reduce the motor torque?

Different winding methods give different parallel paths, and different values for A. For a simplex lap winding, A = P. For a wave winding, A = 2. I'm guessing that the number of parallel paths are the number of winding conductors connected in parallel. These winding conductors in parallel will each distribute the supply current equally, hence dividing the current, I, by the factor A. I'm not entirely sure this is correct however, and I'm having difficulty visualising this (i.e. I can't tell by looking at a winding diagram the value of A).

Any help in better understanding this term would be greatly appreciated.

References:
http://www.electrical4u.com/torque-equation-of-dc-motor/
http://www.electrical4u.com/lap-winding-simplex-and-duplex-lap-winding/
 

Answers and Replies

  • #2
423
118
In above article it is mentioned:

“Ia, Ra are the armature current and armature resistance”

In your above formula I it is actually Ia -total current of armature- then Ia/A it is the current

per conductor. If Ia/A remains constant the torque will stay the same.
 

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