Reliable current sensing for inverter-controlled electric machine

Abstract

Phase currents of an inverter-driven electric machine are measured by mounting phase conductors of each respective phase current into a central passage of a respective flux core. A plurality of current sensors are mounted into a gap of each respective flux core to generate a respective plurality of current signals for each phase current. The Hall-effect devices are connected to a plurality of multi-channel op amp devices for conditioning the current signals such that each set of Hall-effect devices is connected to a different one of the op amp devices and such that each op amp device receives one current signal corresponding to each phase current. Thus, a valid conditioned current signal corresponding to each phase conductor is generated by the op amp devices unless there are multiple simultaneous failures of the Hall-effect devices and the op amp devices.

What is claimed is: 
     
         1 . A multi-phase electric motor current-measuring method comprising:
 magnetically coupling respective pluralities of Hall devices to respective motor phases to generate respective phase current measurements; and   amplifying the current measurements in a plurality of multi-channel amplifiers such that measurements for each respective phase are amplified by a different amplifier, whereby a valid current measurement is generated for all phase currents unless there are multiple failures of the Hall devices and the amplifiers.   
     
     
         2 . The method of  claim 1  wherein each plurality of Hall devices is magnetically coupled to a conductor of the respective motor phase by a respective flux core disposed around the respective conductor. 
     
     
         3 . The method of  claim 1  further comprising:
 converting the amplified current measurements in a plurality of analog-to-digital converters, wherein each multi-channel amplifier is connected to a different respective analog-to-digital converter.