Patent ID: 8159167

Claim:
An electronically commutated motor ( 20 ) comprising: a rotor ( 28 ) and a rotor position sensor ( 30 ) associated therewith, which sensor, during operation, furnishes a rotational position signal ( 34 ), at least at predetermined rotational positions of the rotor ( 28 ), a stator interacting with the rotor ( 28 ), said stator having at least one stator winding strand ( 26 ) that is arranged in the diagonal ( 24 ) of an H bridge ( 22 ), the H bridge including a first semiconductor switch (S 3 ), a first connection of said first semiconductor switch (S 3 ) being connected to a first side ( 52 ) of the winding strand ( 26 ), a second connection of said first semiconductor switch (S 3 ) being connected to a connecting lead ( 62 ), the H bridge also comprising a second semiconductor switch (S 4 ), a first connection of said second semiconductor switch (S 4 ) being connected to a second side ( 54 ) of the winding strand ( 26 ), a second connection of said second semiconductor switch (S 4 ) being connected to said connecting lead ( 62 ), wherein the H bridge ( 22 ) is configured on a first side ( 44 ) for connection to a first pole ( 46 ) of a DC voltage source, and is configured at the connecting lead ( 62 ) for connection to a second pole ( 50 ) of said DC voltage source, the connecting lead ( 62 ) being connected via a measuring resistor ( 59 ) to the second pole ( 50 ), through which measuring resistor ( 59 ) a current (iR) flows to the H bridge ( 22 ), during operation, and thereby causes a corresponding voltage drop (uR) in the measuring resistor ( 59 ), and a control apparatus ( 36 ) which, during operation, performs the steps of: measuring a current-dependent signal (u 67 ) that is derived from said voltage drop (uR) at said measuring resistor ( 59 ), controlling the H bridge ( 22 ) so that the stator winding strand ( 26 ) associated therewith has current pulses (+i 1 , −i 1 ) flowing through it, between which pulses, adjacent a first point in time (t 1 ) that is influenced by a rotational position signal ( 34 ) of the rotor position sensor ( 30 ), the flow direction, of the current delivered to the stator winding strand ( 26 ), is switched over by a commutation operation to a direction opposite to the previous current flow direction; starting from a second point in time (t 2 ) which is in advance of said first point in time (t 1 ), operating the stator winding strand ( 26 ) in short circuit, by corresponding control of the H bridge ( 22 ), in order to cause a decreasing loop current (I*) through the stator winding strand ( 26 ); and performing modification steps of the second point in time (t 2 ), as a function of said current-dependent signal (u 67 ), in order to modify the current (i 1 , i 1 ′) flowing in the winding strand ( 26 ) at a first point in time (t 1 ), toward a minimum.