Current Measurement Gain Tuning Using High-Frequency Signal Injection

Accurate measurement of phase currents in electric machines is a requirement for most high-performance drives. Incorrect current measurement gain estimates, caused by device tolerances, temperature drift, age, and noise, reduce the accuracy of the current measurements and degrade the drive´s performance. This paper presents a method for compensating current measurement gain errors using a periodically injected high- frequency voltage. The positive and negative sequence components of the resulting high-frequency current are measured and used for balancing and scaling the phase current measurement gains. The method can be used either as part of an initial commissioning, or start-up sequence, or periodically during the regular operation of the machine.