Improvements in the Hysteresis and Cogging Evaluation with an Innovative Methodology

The paper presents an innovative methodology to detect the cogging and hysteresis torque in radial flux machines. The study moves from the traditional way adopted to measure them, that is by conventional no load tests; the experimental procedure here proposed is described in details, highlighting the advantages with respect to the previous method. A cheaper test bench is needed, as the gearbox is avoided, and a stepper motor in place of a DC motor is adopted to move the system. The procedure has been tested on two identical machine structures, but with different stator materials (traditional laminated steel and Soft Magnetic Composite material); a comparison with the results obtained with traditional no load tests has been performed to validate the proposed procedure. The novel method is more accurate in the detection of the cogging torque, even if requires a measurement time slightly longer (about 30 minutes of duration).