This paper presents a low-cost fault-tolerant system for open-phase fault (OPF) in a converter-fed permanent-magnet synchronous machine. The proposed fault-tolerant system is based on field orientation control with additional fault tolerance functionality. A current predictive method for OPF detection is presented, together with an estimation of the threshold level for detection. The proposed method is based on the prediction of stator current for the next sampling interval. Furthermore, a new method for postfault operation of the machine is proposed. For optimal performance of the complete drive, a prefiring angle is introduced in order to avoid the temporary generation of negative torque. This improvement increases the average generated postfault electromagnetic torque, and consequently, it reduces the mechanical stress on various machine parts. The proposed fault detection and postfault operation solutions were simulated in MATLAB, and they were also tested on an experimental setup. The results show several advantages of the proposed fault-tolerant solution, like its short fault-detection time, substantial robustness against variation of machine parameters or load fluctuations, and negligible implementation costs, since no hardware modifications are needed. The fault detection algorithm does not require high computing power, and it operates well even during transients.
COBISS.SI-ID: 11176276
A universal high frequency three phase electric motor model to be used in the design process of the electric motor drive systems is proposed. The model can be combined with the models of the filter, cable and inverter to form a complete drive system. It allows for a common and differential mode high frequency analysis in studying the bearing currents, electromagnetic interference and overvoltages in the motor windings caused by the high frequency reflections. The model phase is symmetrical meaning that the beginning and end of each phase are equal and the central part is inserted between them. This enables modelling of both the delta and star winding connections of the three phases. The equations used to calculate the model parameters are presented. They are based on the common and differential mode impedance measurements. The model can be simplified when considering only electric discharge machining bearing currents, as they are affected only by the common mode states. A simplified model to be used in the delta winding connection is also presented. The model calculated common and differential mode impedances are compared with the impedances measured on a 6.5 kW outer rotor brushless direct current motor. The paper ends by providing the obtained simulation and measurement results for the common and differential mode.
COBISS.SI-ID: 10861908
Vascular endothelium selectively controls the transport of plasma contents across the blood vessel wall. The principal objective of our preliminary study was to quantify the electroporation-induced increase in permeability of blood vessel wall for macromolecules, which do not normally extravasate from blood into skin interstitium in homeostatic conditions. Our study combines mathematical modeling (by employing pharmacokinetic and finite element modeling approach) with in vivo measurements (by intravital fluorescence microscopy). Extravasation of fluorescently labeled dextran molecules of two different sizes (70 kDa and 2000 kDa) following the application of electroporation pulses was investigated in order to simulate extravasation of therapeutic macromolecules with molecular weights comparable to molecular weight of particles such as antibodies and plasmid DNA. The increase in blood vessel permeability due to electroporation and corresponding transvascular transport was quantified by calculating the apparent diffusion coefficients for skin microvessel wall (D [%m2/s]) for both molecular sizes. The calculated apparent diffusion coefficients were D = 0.0086 %m2/s and D = 0.0045 %m2/s for 70 kDa and 2000 kDa dextran molecules, respectively. The results of our preliminary study have important implications in development of realistic mathematical models for prediction of extravasation and delivery of large therapeutic molecules to target tissues by means of electroporation.
COBISS.SI-ID: 1980027
The presented survey includes a comprehensive overview of mechanical failure mode causes for direct driven electric in-wheel motors. As electric vehicles evolve and develop, in-wheel motor driven vehicles gain acknowledgement, more and more papers are published in order to show individual design challenges and overcoming solutions for failure causes and effects. Obtainable literature is mainly concerned with integral electrical failure modes, neglecting structural causes and effects which in some cases interact. The presented paper inspects the most likely potential mechanical causes of failure modes for in-wheel motors and shows related papers' results for comparison and reference. As several mechanical and electromagnetic layouts and construction topologies exist, only the most promising and generally used one has been studied within this work in order to emphasize sensible directions of further development. Failure mode and effects analysis (FMEA) has been made with severity rating which present mechanical failure potential for permanent magnet synchronous motors intended for in-wheel motor application.
COBISS.SI-ID: 13856283
The article reviews current transducers that are most commonly used in the field of power electronics. The advantages and disadvantages for each transducer type were critically evaluated and their parameters were also tested. The dynamic properties were assessed with step response, while the frequency response test was used for evaluating signal to noise ratio and total harmonic distortion.
COBISS.SI-ID: 11121492