Patent ID: 7589489

Claim:
An electronically commutated motor comprising: a permanent magnet rotor ( 960 ); a stator having a first winding strand ( 102 ), associated with which is a first field-effect transistor ( 106 ) that, under the control of a potential at a control electrode (G) thereof, serves during operation to control the current through the first winding strand ( 102 ); a second winding strand ( 902 ), associated with which is a second field-effect transistor ( 906 ) that, under the control of a potential at a control electrode (G), serves during operation to control the current through the second winding strand ( 902 ), the first field-effect transistor ( 106 ) and the second field-effect transistor ( 906 ) being adapted to be switched on alternately during operation under the control of commutation operations; a first source ( 112 , 510 ) of control signals (VT 1 , 1202 ) for controlling the first field-effect transistor ( 106 ); a second source ( 912 , 914 ) of control signals (VT 2 , 1204 ) for controlling the second field-effect transistor ( 906 ); a first measuring apparatus ( 510 ) for sensing the potential at the control electrode of the first field-effect transistor ( 106 ); a second measuring apparatus ( 914 ) for sensing the potential at the control electrode of the second field-effect transistor ( 906 ); a program controlled arrangement ( 108 ) which is implemented to carry out, during operation, the following steps: during a commutation operation, switching to a high impedance the control electrode of that one of the two field-effect transistors ( 106 , 906 ) that is controlled to be conductive at that instant is switched to high impedance; using the measuring apparatus ( 510 , 9140 associated with the current conductive field-effect transistor to sense any changes in potential at the control electrode (G) thereof; and after said potential has reached a predetermined degree of switch-off (A) of the associated field-effect transistor, applying a switch on signal to the control electrode of the other field-effect transistor from the source ( 112 , 510 ) for control signals associated with said transistor.