An electric motor supplied by a battery source is controlled by receiving an input torque demand signal indicative of the amount of torque demanded from the motor and producing as an output a set of motor current demand signals. A drive stage receives the motor current demand signals and causes currents to flow in each phase of the motor as required to meet the demanded torque. A torque demand limiter outputs a torque demand limit signal indicative of a torque demand limit, above which the battery current would exceed one or more limits. The torque demand limiter may set the value of the torque demand limit signal using a model of the motor and the drive or as a function of the voltage of the battery. The torque demand limiter may use one or more of the following parameters when determining the torque limit: motor battery current limit, generator battery current limits; motor electric power limit; generator electric power limit. A torque demand generator may generate a torque demand signal having a value dependent on the amount of assistance torque demanded from the motor. The arrangement may be used to control a motor of an electric power steering system.
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