Electric machine with permanent magnetic rotor

An electric motor ( 10 ) comprises a stator ( 20 ) having a primary winding and a rotor ( 130 a,b) arranged to rotate in the stator ( 20 ). The rotor comprises a shaft ( 160 ), a first magnetic rotor component ( 140 ) and a second magnetic rotor component ( 150 ), each magnetic rotor component ( 140,150 ) having a magnetic pole of a first polarity ( 43,43',53,53 ') and a magnetic pole of a second polarity ( 47,47',57,57 '). At least one of the first and second rotor components ( 140,150 ) further comprises a structure ( 35 ) for carrying induced eddy currents. The second magnetic rotor component ( 150 ) is rotatable with respect to the first magnetic rotor component ( 140 ) around the shaft ( 160 ) from a low-flux orientation to a high-flux orientation. The motor ( 10 ) is arranged such that the second magnetic rotor component ( 150 ) is in the low-flux orientation when the rotor ( 130 a,b) is at rest and is in the high-flux orientation when the rotor ( 130 a,b) is rotating at an operating speed.