Patent ID: 8981693
Filing Date: 2015-03-17
Classification: G01R,H02P

Abstract:
1. A method for determining a time of a zero crossing of a winding phase current in a polyphase electric machine ( 2 ), the electric machine ( 2 ) being actuated with the aid of a driver circuit ( 31 ; 50 ) with power switches ( 36 ; 37 ; 52 , 53 ) in order to provide a plurality of phase voltages, which are applied to connection nodes (A 1 , A 2 , B 1 , B 2 ) of the electric machine ( 2 ) which are associated with corresponding phases, at least some of the power switches ( 36 , 37 ; 52 , 53 ) being actuable cyclically on the basis of pulse width modulation with a duty factor in order to apply different potentials alternately to one of the connection nodes (A 1 , A 2 , B 1 , B 2 ), said method comprising the following steps: actuating the driver circuit ( deactivating the pulse-width-modulated actuation for at least one of the power switches ( detecting a diode voltage across a freewheeling diode, with which the deactivated power switch ( fixing the time of the zero crossing of the winding phase current as the time after which, within the time segment, there is no longer a diode voltage present across the freewheeling diode (