Brushless electric motor or generator in shell construction

A method of operating an electric motor, comprising:

• providing an electric motor comprising:
• at least two coaxially aligned stators disposed about a central axis and a rotor concentric to the at least two stators about the central axis, wherein
• each stator comprises at least two poles,
• and wherein the rotor comprises at least two magnets arranged about the circumference of the rotor, such that each pole of the stators faces a corresponding magnet of the rotor and the azimuthal center of each pole is radially facing the azimuthal center of a corresponding magnet,
• wherein each stator has at least one coil or winding common to the poles,
• wherein the at least two stators are mutually angularly offset by each other such that poles of at least one of the stators are angularly offset to the poles of at least the other one of the stators by an angle of 360°(k×2n) with respect to the central axis, where k equals the number of stators and is a positive integer greater than or equal to 2 or multiples of two thereof, and where n equals one-half the number of poles per stator and is a positive integer greater than or equal to 1,
• wherein the electric motor further comprises a control unit, a rotor position detecting means and one bridge circuit connected to the at least one common coil or winding of each one of the at least two stators, and
• wherein each one of the bridge circuits comprises four power switches connected to the at least one coil or winding of the stator,
• providing a first polarity of voltage supplied to the at least one coil or winding, where a first pair of power switches is activated and a second pair of power switches is deactivated;
• and
• providing a second polarity of voltage supplied to the at least one coil or winding, where the second pair of power switches is activated and the first pair is deactivated;
• wherein the control unit controls the power switches in dependency of the rotor position and motor power demand and is adapted to execute the following steps:
• detecting the rotor position using the rotor position detecting means;
• and changing the polarity of the voltage supplied to each of the at least two stators in dependency of the rotor position, wherein the polarity of each of the at least two stators is changed at a different rotor position.