Temperature-Rise Determination Test for Synchronous Reluctance Machines Applying Superposition and Equivalent-Loading Methods

Since synchronous reluctance machines (SynRMs) can realize high efficiency without permanent magnets, their application has recently expanded to larger machines. For large machines, indirect measurement based on superposition and equivalent loading methods is preferred to determine the temperature rise from the viewpoint of reducing the burden on test equipment, but the method is not authorized for SynRM. This paper performed the conventional method to a 400 kW-8488 N.m SynRM on trial 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 occurs during the equivalent load test, and its heating affects the determination result. This paper finally demonstrated that a new method, which estimates the temperature-rise rate from the two equivalent load tests performed under the different stator current conditions, effectively eliminates the damping loss effect and determines the temperature rise with a slight error of 4 K.