Identification of the Magnetic Model of Permanent-Magnet Synchronous Machines Using DC-Biased Low-Frequency AC Signal Injection

This paper proposes a simple procedure for accurate identification of the magnetic model of permanent-magnet synchronousmachinesthroughinvertersupply.Theproposedmethod accounts for the magnetic saturation and the cross-saturation effects. The identification methods reported in the literature may require a servomotor to drive the motor under test at controlled constant speed or the motor itself must accelerate and decelerate. The technique proposed here can be applied at standstill with or without rotor locking and uses a dc+ac injection strategy to identify the machine inductances to construct its magnetic model. The direct current sets the operating point, whereas the superimposed ac component estimates the inductance at that particular point. Small ac signal is injected to ensure local linearity of the magnetic characteristic. Saturation effects are automatically accounted for by the dc bias level, and cross-saturation effects are quantified through maintaining a constant current along the cross-axis. The magnetic model thus obtained can be used for optimal control of the machine and for accurate torque estimation in vectorcontrolled drives

Performance analysis of slope and frequency modulated carrier PWM methods for grid connected converters

A detailed analysis of two Pulse-Width Modulation (PWM) methods is performed in this paper for grid connected converters. The considered methods are: sinusoidal carrier regulated by the slope of a trapezoidal waveform PWM (SLPWM) and frequency modulated triangular carrier PWM (HIPWM-FMTC). The analysis of the two PWM methods is realized with four performance indicators: standard and weighted total harmonic distortion (THD and WTHD), fulfillment of the grid connection requirements and minimum pulse width. The results are compared with those obtained for the Space Vector Modulation (SVPWM) and Selective Harmonic Elimination PWM (SHE-PWM). Experimental results are presented for a 1 kVA inverter prototype to validate the paper conclusions

Recent archaeological researches in the Vârghiș Gorges karst area (Eastern Carpathians, Romania). A synthesis of the 2014–2020 campaigns

The Vârghiș Gorges karst system (Perșani Mountains, Eastern Carpathians) constituted a point of interest for speleologists, paleontologists and archaeologists since the second half of the 19th century. Their efforts succeeded in highlighting the notable archaeological potential of the area, although the actual research results were not always thoroughly reported. Since 2014, our team reunited specialists from 10 different institutions and various fields of research and initiated archaeological excavations, coupled with achaeozoological, sedimentological and chronometric investigations, in several caves within the Vârghiș Gorges. As the paper below will show, although the results obtained so far are definitively informative, further investigation are clearly needed, in order to accurately clarify aspects pertaining to the intricate cultural and chronological framework.Sistemul carstic din Cheile Vârghișului (Munții Perșani, Carpații Orientali) a reprezentat un punct de interes pentru speologi, paleontologi și arheologi încă din a doua jumătate a secolului XIX. Demersurile acestora au evidențiat remarcabilul potențial arheologic al zonei, chiar dacă rezultatele investigațiilor propriu-zise nu au fost întotdeauna prezentate exhaustiv. Începând cu anul 2014, am alcătuit o echipă de specialiști din zece instituții de cercetare și variate domenii de specialitate și am inițiat săpături arheologice, însoțite de cercetări arheozoologice, sedimentologice și cronometrice, în câteva peșteri din Cheile Vârghișului. Așa cum reiese din observațiile prezentate, deși rezultatele obținute până în prezent oferă informații noi, cercetări viitoare sunt necesare pentru o mai bună înțelegere a complexității cadrului cronologic și cultural.Cosac Marian, Murătoreanu George, Veres Daniel, Niţă Loredana, Schmidt Cristoph, Hambach Ulrich, Radu Alexandru, Cuculici Roxana, Buzea Dan Lucian, Ștefan Dan, Mărgărit Monica, Vasile Ştefan, Dumitraşcu Valentin, Roşu Mariana, Petculescu Alexandru, Sava Tiberiu, Georgescu Valentin, Șerbănescu Gabriel, Geambașu Ionel. Recent archaeological researches in the Vârghiș Gorges karst area (Eastern Carpathians, Romania). A synthesis of the 2014–2020 campaigns. In: Materiale şi cercetãri arheologice (Serie nouã), H-S 2021. pp. 325-350