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Usually, any electric switching triggered to initiate a fault or to disconnect an electric circuit is followed by transient phenomena with occurrence of over voltages, called transient switching overvoltages. The theoretical and practical importance to know and evaluate correctly these overvoltages is related to the reliability of electric systems and of their component parts, as it is wellknown the fact that any type of overvoltage shall generate additional strains in the electric insulations and potential hazards related to the breaking or creepage of insulations. For the limitation of switching overvoltages, two types of overvoltage suppressing circuits (one type with passive components and one type with active components in two variants) have been proposed, tested, experimented and constructed, as a result of researches developed in our group. [ABSTRACT FROM AUTHOR]

The electric power drive systems consisting of three phase induction motor and static frequency converter are designed to enhance the performance on site, by diminishing the energy consumption, optimization of the technological processes and the reduction of costs for the maintenance and repairs of the equipment. The paper presents some important issues concerning the selection of inverter fed flameproof electric drives in the field of potentially explosive atmospheres of gases and vapors by ensuring a correct risk management against the hazard of electric sparks as well as excessive temperatures [ABSTRACT FROM AUTHOR]

The type of protection flameproof enclosure applies generally to electrical apparatus which in normal operation produces electrical arcs and sparks, and consists in placing the parts that could ignite an explosive atmosphere inside of an enclosure that can withstand the pressure developed during an internal explosion of an explosive mixture and which prevents the explosion transmission to the explosive atmosphere surrounding the enclosure. The paper presents the most important aspects that must be taken into account when running tests in explosive mixtures (determination of explosion pressure, overpressure test, test for non-transmission of an internal ignition) for verification of flameproof character of the enclosure for explosion-proof electrical equipments with the type of protection flameproof enclosure. [ABSTRACT FROM AUTHOR]