1. Interaction of Magnetic Fields (Motor Action)
Look at adjacent current-carrying conductors
Currents in opposite directions
Flux “bunching” between the conductors
Force of repulsion acts to separate the conductors
ECE 441

2. Interaction of Magnetic Fields (Motor Action)
Currents in the same direction
Flux in space between conductors in “opposite” directions
Force of attraction acts to pull the conductors together
ECE 441

3. Elementary Two-Pole Motor
Rotor core with 2 insulated conductors in “slots”
A stationary magnet – the “stator”
ECE 441

4. Current-Carrying Conductor in a Magnetic Field
ECE 441

5. Current-Carrying Conductor in a Magnetic Field
Current-carrying conductor perpendicular to the B-field
ECE 441

6. Magnitude of the force on the conductor in a Magnetic Field
Magnitude of the mechanical force on the conductor is
Where F = mechanical force (N)
B = flux density in the stator field (T)
= the effective length of the rotor conductor
I = current in the rotor conductor (A)
ECE 441

7. Conductor “skewed” to the B-field by angle 
= effective length of the rotor conductor (m)
ECE 441

8. Single-Loop Rotor Coil Carrying a Current Situated in a Two-Pole Field
ECE 441

9. Torque produced by the 2-conductor couple
ECE 441

10. Elementary Two-Pole Generator
ECE 441

11. Voltage induced in the coil, e
Flux through the coil window is sinusoidal
Φ = Φmaxsin(ωt)
Voltage induced in coil,e
e = N(dΦ/dt)
e = NωΦmaxcos(ωt)
Emax = ωNΦmax
Emax = 2πfNΦmax
Erms = 4.44fNΦmax
ECE 441

12. Directions of induced voltage and current
Develop CCW counter-torque
“Bunching” must occur at the top of coil side B and the bottom of coil side A
Coil current is CCW as viewed from south pole
ECE 441