Magnet Temperature Estimation in Variable Leakage Flux Permanent Magnet Synchronous Machines Using the Magnet Flux Linkage

Abstract

Permanent magnet synchronous machines (PMSMs) performance is highly dependent on the Permanent Magnets (PMs) temperature. Knowledge of the PMs temperature is therefore of great importance both for control and monitoring purposes. An increase in the PM temperature during motor operation, decreases PMs magnetic flux strength and consequently the PMSM torque production capability, eventually causing irreversible demagnetization of the PMs; for the case of variable leakage flux PMSMs (VLF- PMSMs), it will affect the variable leakage property of the machine, which will place additional concerns on the machine control. This paper proposes a PM temperature estimation method for VLF-PMSMs from the PM flux linkage. PM flux linkage is obtained from the response of the machine to a small-amplitude, low frequency, square-wave signal (either voltage or current). The signal is injected on top of the fundamental excitation, allowing on-line temperature estimation without interfering with the operation of the machine