ECE 442 Power Electronics1 Elementary Two-Pole Motor

ECE 442 Power Electronics2 Elementary Two-Pole Generator

ECE 442 Power Electronics3 Voltage induced in the coil, e Flux through the coil window is sinusoidal Φ = Φ max sin(ωt) Voltage induced in coil,e e = N(dΦ/dt) e = NωΦ max cos(ωt) E max = ωNΦ max E max = 2πfNΦ max E rms = 4.44fNΦ max

ECE 442 Power Electronics4 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 442 Power Electronics5 Basic DC Generator Separately Excited Shunt Generator

ECE 442 Power Electronics6

7 Generator Action Permanent-magnet field One-turn armature Drive so that E a >E bat Current I a flows to charge E bat

ECE 442 Power Electronics8 From a Circuit Point-of-View “Generate” voltage E a When supplying current, the machine develops a “counter- torque” in opposition to the driving torque

ECE 442 Power Electronics9 Motor Action “Uncouple” the Prime Mover Eventually, E a will decrease so that E a <E bat I a flows as shown Armature turns in the same direction

ECE 442 Power Electronics10 From a Circuit Point-Of-View Counter-emf, E a, is induced, opposing the driving voltage E bat Machine develops a driving torque