This paper presents an encoderless highperformance synchronous reluctance motor drive for traction applications. The control system is based on the active flux concept and a hybrid rotor position estimation algorithm is used, being this algorithm based on the injection of highfrequency signals at low speeds and on the position of the active flux vector for medium and high-speeds. A smooth transition algorithm between the two rotor position estimation methods is provided. Moreover, in order to improve the efficiency of the overall drive system, a loss minimization algorithm is proposed in order to reduce the motor copper losses when operating in steady-state. Experimental results obtained in the laboratory confirm the validity and adequacy of the proposed algorithms for the developed drive system.
In this study, we compare the tribological performance of a multilayer TiSiN/Ti(Ag)N coating with a TiSiN/TiN coating with a similar Si content in order to demonstrate the effect of the solid lubricant phase, silver. For Al2O3 balls, the hardness and reduced modulus determine the tribological performance of the coatings for tests conducted at room temperature (RT) against Al2O3 balls. At 550 °C, the TiSiN/TiN coating failed, whereas the Ag-containing coating performed better due to the presence of Ag in the contact, which decreased the shear stress and, consequently, the friction. For tests against TiAl6V4 balls, the Ag-containing coating was always better than the TiSiN/TiN one. At 550 °C, Ag in the wear track prevented the adhesion of the oxidized Ti-alloy wear debris in the contact, favoring the adhesion of wear debris from the coating to both the coating and counterpart surfaces. No wear could be measured for the 700 °C tests for both coatings due to different reasons: (i) the presence of oxidized adhered material from the ball to the reference TiSiN/TiN coating surface protected from wear and (ii) the presence of Ag-agglomerated particles decreased the friction and minimized the adhesion wear of the counterpart for the TiSiN/TiN(Ag) coating.
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