Patent ID: 6914409
Filing Date: 2005-07-05
Classification: H02P

Abstract:
1. A current detection method for an electric motor which detects phase currents of the electric motor driven by a power converter that provides ON/OFF control of bridge-connected switching elements, based on a pulse-width modulation excitation pattern, to convert a direct current into poly-phase alternating currents, said method comprising: connecting a current detecting element which produces a signal corresponding to a current value at the direct current side of the power converter; changing the pulse-width modulation excitation pattern by executing a shift of time of any of the phases of the pulse-width modulation excitation pattern so that there results a combination of: (i) a time period in which two phase currents flow at the same time for a time period more than a minimum standby time τ, and (ii) a time period in which at least one of the two phase currents independently flows for a time period more than the minimum standby time τ, so that a signal directly or indirectly corresponding to the phase currents is produced at the current detecting element, wherein the minimum standby time τ corresponds to the time interval from when the ON/OFF state of at least one of the switching elements changes until the time when a signal produced at the current detecting element is read; and detecting phase currents of the electric motor based on the signal produced at the current detecting element and the excitation pattern which has been changed.