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

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

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

Current-Carrying Conductor in a Magnetic Field ECE 441

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

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

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

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

Torque produced by the 2-conductor couple ECE 441

Elementary Two-Pole Generator ECE 441

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

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