A method arranged to control a motor for driving a load is disclosed. The motor and load form at least a part of a system and the motor comprises a stator arranged to produce a varying magnetic field responsive to an applied AC voltage and a rotor arranged to rotate responsive to the varying magnetic field produced by the stator, the rotor rotating at a speed synchronized to a frequency of the applied AC voltage. The method comprises receiving a target rotor speed, determining a voltage level for the applied AC voltage for producing a magnetic field having magnetic flux of sufficient magnitude to maintain the rotor in synchronization with the frequency of the applied AC voltage when rotating at the target speed of rotation. The voltage level is determined in accordance with the target rotor speed and a model of the system. The model comprising a plurality of model elements, wherein one or more of the model elements is indicative of an effect of one or more parts of the system on rotation of the rotor when the speed of the rotor is constant and one or more of the model elements are indicative of an effect of one or more parts of the system on rotation of the rotor when the speed of the rotor is dynamic. The method further comprising applying the applied AC voltage to the stator at the determined voltage level and at a frequency required to provide the target rotor speed.