Rotor permanent magnet condition has a direct influence
on the PM motor. The induced voltages by the permanent
magnet (back electromagnetic force, back-EMF) together with
the inverter-fed terminal voltages decide the overall
performance of the motor. Equation (6) shows the relationship
between motor voltage, current and permanent magnet flux. In
it abc u is motor terminal voltage, abc i is phase current, abc ψ is
rotor permanent magnet flux linkage coupled to motor stator
winding. These electrical variables are symmetrical in time
domain, with a 120 degrees difference between a, b and c
phases if motor is properly controlled.