... (torque) in N-m, ω in radians/sec, α in radians/sec2, I in kg-m2, α = dω / dt I is a 3x3 matrix, not necessarily diagonal If T = 0, then I α = - ω x I ω which is usually non-zero So α is non-zero, ... are 3-phase Speed up to 7200 rpm: speed ~ 7200 / # “poles” of the motor Induction motors are brushless (no contacts between moving and fixed parts) Hi reliability Efficiency high: 5 0-9 5 ... voltage at equally-spaced phases: Single phase AC requires two wires (only 1/3 the current or power of 3-phase) AC induction Motors Induction motors – simple, cheap, high-power, high torque,...