Important parts of in-wheel motor development are testing and verification. The tests are carried out on dedicated measuring stations of greater power or in a simplified system where two identical motors are connected via couplings and torque transducer (back-to-back test configuration – BB). The BB testing method is evaluated in the first part of a thesis. Because of its time-consuming nature and expensive measuring system, the BB testing method is suitable for the development phase, less so for the manufacturing phase and testing during the motor's lifespan.
The doctoral thesis titled "Self-loading method for electric in-wheel motor testing" introduces an alternative testing method to determine motor efficiency and its temperature rise. In the BB testing method, the loading of the motor axis is replaced with the dynamic performance of rotor inertia. To simulate the synthetic loading method, we have developed a simulation model of the entire propulsion system, which was compared to measurements obtained on an actual propulsion system. We wanted to upgrade the synthetic loading testing method to enable motor efficiency measurement on a broader operating area and not only in the nominal operating point. We have upgraded the simulation model with the trapezoidal current reference, which reduces the ratio between the amplitude and effective value of phase currents. The results of the motor's efficiency, measured with the BB method, confirm the simulation results using the synthetic loading method. The analytical equations of motor losses confirm that the losses with classical BB and synthetic loading methods are comparable. To achieve the equivalent loss in both testing methods, we present an analytical model which determines the specific shape of synthetic loading current reference. In conclusion, the measured values of motor efficiency using the synthetic loading method are compared with the classical BB testing method in twenty motor operating points.
The doctoral thesis presents also a measuring method for rotor inertia determination, phase currents and voltages measuring equipment optimization, and a method to measure the air gap directly. The conclusion presents the main takeaways and contributions to science.
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