Abstract:The reliability of power electronic devices and components is very important to manufacturers. In recent years, many researchers have conducted reliability assessments of power electronic devices, yet the reliability of numerous circuits used widely has not been evaluated. This paper presents a comprehensive reliability evaluation of fundamental multilevel inverters. The reliability of the multilevel inverters is analyzed by calculating the mean time to failure for each component. The calculation was performed by two methods (approximate and exact) to achieve better comparisons. The approximate method is similar to the parts count method used in MIL-HDBK-217 reliability standard, and the exact method exhibits the parts stress method. In the exact method, due to the direct relationship between component failure and temperature, we used Matlab Simulink to determine power losses in diodes and switches taking into account the temperature factor. The results determined by the approximate method showed that the three-level cascade H-bridge was the most reliable of the inverters considered. Although the exact method validates those results, and shows that cascade H-bridge (CHB) had a longer lifespan, but the calculated values are different. Therefore, using different approaches for evaluating reliability results in different outcomes.
In this study, an optimal design of a new line-start permanent magnet synchronous shaded-pole motor (LSPMSSPM) is proposed. A genetic algorithm optimisation method based on transient two-dimensional finite-element method (FEM) is applied to reach a global optimum design. Advantages and challenges of the proposed LSPMSSPM are investigated, and its performance characteristics are calculated. Efficiency, power factor, starting behaviour and cost as important key factors are analysed. Finally, FEM results are verified with experimental tests. Nomenclature SY stator yoke Lfe stator and rotor stack length CL coil length CW coil width N turns of stator coil WG wire gauge BW stator bridge air-gap width BH stator bridge air-gap height BC stator bridge air-gap centre position α angle of stepped air-gap α0 starting angle of stepped air-gap SAB air-gap step at beginning SAE air-gap step at end θ1 angle of shading 1 θ2 angle of shading 2 RSH1 radius of shadings 1 RSH2 radius of shadings 2 RD rotor diameter NR number of rotor slots RSH rotor slot height RTW rotor tooth width MT magnet thickness ORM outer radius of magnet RR rotor rib BJ distance between rotor air-bridge and slot bottom BT rotor air-bridge thickness JML motor and load moment of inertia
Solar energy usage is thriving day by day. These solar panels are installed to absorb solar energy and produce electrical energy. As a result, the efficiency of solar panels depends on different environmental factors, namely, air temperature, dust (aerosols and accumulated dust), and solar incidence, and photovoltaic panel angles. The effects of real conditions factors on power and efficiency of photovoltaic panels are studied in this paper through testing the panel in real environmental tests. To study the mentioned parameters precisely, two panels with different angles are used. The case study is regarding a region of Tehran, Iran, in summer and winter seasons. The results show that panel efficiency during winter is higher than summer due to air temperature decrement. It is discovered that among air pollutants, Al and Fe have the most share in polluting the air that affect the photovoltaic efficiency. Moreover, measuring the accumulated dust on the panels shows more amount in winter in comparison with summer. The important point in studying the effect of tilt angle is that inconformity between solar incidence and photovoltaic panel angles would result in solar radiation absorption and eventually panel efficiency loss and also, photovoltaic panel installation angle would affect the amount of dust deposited on its surface.
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