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Reference: ISH2015_93

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Selection of a Switching Element to characterize the Dynamic Behavior of DC Sources



The increasing number of DC applications demand new requirements to switching elements. Especially for surge protective devices the power which they have to handle depends on the different kind of DC technologies. For this reason the dynamic behaviour of the circuit in which they should operate has to be determined reliably. This paper describes the important parameters for switching devices in DC sources. Furthermore, the selection of a switching element for DC circuits is described. Due to the low switching times semiconductor switches are suited for determining the time constant of DC circuits. In addition with semiconductor switches there are no arcs during the switch-off process, whose extinction would cause problems at the DC current. Concurrently, the low switching times are also bringing problems. During the switch-off process large overvoltages occur, which make a determination of the dynamic behaviour difficult. To protect the source and the switching element a surge protective device must be used. For this purpose a metal oxide varistor is used. Investigations, described in this paper are showing that the limiting voltage increases with increasing switch-off currents. The duration of the overvoltage increases also, so the dynamic behaviour during the switch-off process can't be determined accurately. Switching devices with longer switching times have to be used, to ensure that no overvoltages can occur. Thus an evaluation of current and voltage can be performed without the influences of the overvoltage and the dynamic behavior of the power source can be determined.

File Size: 405,1 KB

Year: 2015

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