Determination of dielectric recovery characteristic of a pyro switch in commutation circuit

Pyrotechnic switches are used for overcurrent protection, e.g. in low-voltage DC circuits (battery disconnector). At fault current interruption, arc voltage built up by the switch must be sufficiently high to drive the current to zero (DC switching principle). Compared to AC interruption, the switch does not experience a transient recovery voltage (TRV). With increasing breaking capacity, comparatively large construction volumes are necessary. Possible reduction in design effort of the switch is found by using the commutation principle where the pyrotechnic switch is integrated as commutation switch in the low-impedance main current path. This publication presents an experimental method for recording the dynamic dielectric recovery characteristics of a pyrotechnical switch for commutation circuits. An electrically equivalent network without a switch-off element in the commutation path was installed in the synthetic test circuit and stressed with currents up to 10 kA. From the moment of successful commutation by the pyrotechnical switch, the switch was loaded with voltages up to 4 kV using an RC circuit for recording the dynamic dielectric recovery characteristic. With the resulting dielectric recovery course and the verification of the switching capacity required for successful commutation, an optimally adapted switch-off element can be selected for realizing the overcurrent protection device based on the commutation principle.


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