Patent ID: 8159172

Claim:
A method for controlling an electric motor by using the PWM technique; the control method comprises the steps of: applying to the clamps of the electric motor an electric voltage (Vm(t)) varying in time, which displays a square waveform and consists of a sequence of pulses having a uniform wave period and a variable width; adjusting the average value of the electric voltage (Vm(t)) applied to the clamps of the electric motor by varying the width of the pulses of the electric voltage (Vm(t)); determining, in the case of a variation of the width of the pulses, the overall required width variation; subdividing the overall required width variation in a determined number of partial variations, the overall sum of which is equivalent to the overall required width variation; and gradually varying the width of the pulses of the electric voltage (Vm(t)) by applying in a sequence to each pulse a corresponding partial variation so that the difference between the width of a pulse and the width of a following pulse is equivalent to the corresponding partial variation; verifying whether the variation of the width of the pulses also implies the inversion of the electric voltage (Vm(t)); and assigning a negative value to the first partial variation, if the variation of the width of the pulses also implies the inversion of the electric voltage (Vm(t)), so as to cancel the width of at least the first pulse after the inversion of the electric voltage (Vm(t)).