Temperature Rise Determination Test for Synchronous Reluctance Machines Based on Equivalent Load Method

Synchronous reluctance machines (SynRMs) can realize high efficiency without permanent magnets, and recently their application has expanded to larger machines. Our group also developed a 400 kW-8488 N‧m SynRM that achieved a world-class continuous rated torque. For such a large torque and high output machine, indirect measurements based on the superposition principle and equivalent load method are preferred in determining the temperature rise. This is beneficial from the viewpoint of reducing the burden on test equipment, but the method is not authorized for SynRM. This paper applied the conventional method to SynRM in experiments and compared its results with the actual load test to assess its applicability. Consequently, it was clarified that the conventional method, consisting of a no-load and a mixed-frequency equivalent load test, overestimates the temperature rise by 25 K or more. Detailed magnetic field analysis revealed that damping loss occurred during the equivalent load test, and its heating affected the temperature rise determination. Finally, we proposed a new method for estimating the temperature rise from the two equivalent load tests performed under the different stator current conditions. It was demonstrated that the method effectively eliminated the damping loss effect and determined the temperature rise with a slight error of 4 K.