Patent ID: 6891348

Claim:
Electric motor ( 1 ) for driving members that rotate at speeds of greater than 40 000 revolutions per minute, comprising a stator ( 2 ) housing induction coils ( 3 i ), a rotor ( 4 ) supporting multiple permanent magnets ( 5 , 6 ) and located coaxially inside the stator ( 2 ), and multiple Hall sensors ( 7 ′, 7 ″, 7 ′″, integral with the stator ( 2 ) and capable of detecting the position of one or more points on the rotor ( 4 ) as it rotates in order appropriately to time the injection of the induction currents into the said coils ( 3 i ) as a function of the position of the permanent magnets ( 5 , 6 ), which motor is characterized in that it is provided with: a) means capable of deactivating all but one ( 7 ′) of the Hall sensors when the speed of rotation of the rotor ( 4 ) exceeds 40 000 revolutions/mm.; b) means capable of measuring the speed of rotation ω n of the rotor ( 4 ) as it describes each n-th revolution by measuring the time taken by a point (P) on the rotor ( 4 ) to perform a predetermined rotation of x degrees with respect to the still-active sensor ( 7 ′) during the said n-th revolution; and c) means capable of bringing about in the next or (n+1)th revolution of the rotor ( 4 ) the injection of the currents into the coils ( 3 i ) as a function of the positions occupied in time by the said point (P) with respect to the abovementioned still-active Hall sensor ( 7 ′), this injection being calculated by considering the speed of rotation of the rotor ( 4 ) in the (n+1)th revolution to be equal to that in the n-th revolution; the said electric motor ( 1 ) having synchronous operation.