The paper presents a virtual laboratory for studying power quality events like three-phase voltage dips, which is used by students to learn and test their knowledge about the subject. The virtual laboratory is needed because in real life, in power quality domain, it is very difficult to generate power quality events in order to see the effects or to analyze their characteristics. The virtual laboratory is designed to give the students the possibility to learn first the theoretical aspects of the subject, then to apply the knowledge they accumulate to several signals, in order to get the characteristics of the event and in the end to test their obtained results with signals characteristics. There are two major advantages of using the virtual laboratory: first is that the students can see different events, with different characteristics, and in this way, they understand better the phenomenon; and the second is that a classical laboratory for studying three phase voltage dips is very expensive, the main elements (programmable voltage sources) having a very high cost.
In the paper are being analyzed the magnetic losses that occur in the induction machines of low and medium power while being supplied by inverters realized with IGBT transistors. The analysis method is based on the over-position effect principle. As a working hypothesis is being neglected the saturation effect. During analyzes is being deduced the computing relations which allow the quality and quantity determination of the magnetic losses in the situation of the deforming supplying system. The theoretical results obtained using the computing program CALCMOT are back-up-ed by the experimental checks realized on two tri-phased induction motors with the powers: 0.37 [kW] / 1500 [rpm], respectively 1.1 kW]/1500[rpm].
The protecting systems against overvoltages produced all over the world make more and more use of variable resistors based on metal oxides known under the name of varistors as they present a series of advantages when compared with other similar protecting systems. In this respect, the paper presents, besides a short comparative analysis of the protecting system, a Romanian concept concerning the realization of protecting modules equipped with ZnO varistors and original experiments which demonstrate their high quality and usefulness.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.