圈上大学 Brushless DC Motors Essential difference-commutation is performed electronically with controller rather than mechanically with brushes V s H +w H3 21 圈上大学 Brushless DC Motor Commutation 2 N Stator Rotor Hall effect sensor Commutation is performed electronically using a controller (e.g.HCS12 or logic circuit) >Similarity with stepper motor,but with less poles >Needs rotor positional closed loop feedback:hall effect sensors,back EMF,photo transistors 22
21 Brushless DC Motors Essential difference - commutation is performed electronically with controller rather than mechanically with brushes 22 Brushless DC Motor Commutation Commutation is performed electronically using a controller (e.g. HCS12 or logic circuit) Similarity with stepper motor, but with less # poles Needs rotor positional closed loop feedback: hall effect sensors, back EMF, photo transistors
圈上大峰 Electromotive Force(电动势) A voltage is induced in a wire moved in a magnetic field >Generators(发电机) eind = (V×B)I Induced Velocity of wire(m/s) voltage (volt) eind is also called electromotive force(EMF感应电动势) eind=vBl (/the wire length) 23 上潘克通大￥ PM DC Motor:Theory of Operation Electromotive Force(EMF): eind =KEng e:induced voltage or EMF K=:EMF constant(motor specific,based on construction) n:rotational speed of the motor [rpm] 24
23 • A voltage is induced in a wire moved in a magnetic field Generators（发电机） B v (l = the wire length) Induced voltage (volt) Velocity of wire (m/s) l eind =vBl eind is also called electromotive force (EMF感应电动势) + + + --- eind Electromotive Force(电动势) eind (v B)l 24 PM DC Motor: Theory of Operation Electromotive Force (EMF): eind KEn eind: induced voltage or EMF KE: EMF constant (motor specific, based on construction) n: rotational speed of the motor [rpm]