Method for measuring the three phase winding curents in a brushless electric motor, comprises reading voltage drop on conducting lower switching element or alternatively on the other similar elements

摘要

A control unit (40) within a control section (3) receives data on torque, motor angle and voltage drop on resistors (317,318,319) in the lower switching branches of an invertor (31). If the voltage drop on a conducting branch resistor does not give a satisfactory result for calculating the motor current due to a low cyclic ratio the voltage drop is calculated from the voltage drops on the other two lower branch switching resistors INDEPENDANT CLAIMS are also included for the following: A control unit which measures motor current by using the voltage drop on a lower invertor switching branch resistor obtained directly or by calculating it from the corresponding voltage drops in the other lower branches A motor system which uses invertor lower switching branch resistance voltage drops obtained directly or derived from other corresponding resistor voltage drops