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AssigneeFraunhofer-Gesellschaft zur Forderung der angewandten
InventorMichael Konstanzer
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In order to reduce the switch-on surge in current in the operation of an inductive load provided with a magnetizable core at an alternating mains current, in particular in pulse group operation, a switch-off-reset impulse is applied to this load following switching-off of the inductive load from the alternating current mains. This impulse has a polarity phased opposite to the last pulse group halfwave. In this way the remanent induction of the transformer core is shifted in a defined manner to lower values so that a defined remanence state of the iron core can be assumed when starting the next pulse group. This permits peak-current-free switching-on under any load and pulse period conditions. The remanent induction of the transformer core can also be maintained in the sector occurring immediately following switching-off of the inductive load, thus at the end of a pulse group. For this purpose voltage of reduced effective value compared to the load, in particular small voltage phases which are in phase with the voltage application prior to the switching-off moment, is applied to the transformer in the pulse group pauses.
A process for the reduction of switch-on surges in current in the operation of an inductive load provided with a magnetizable core at an alternating current mains, in particular a transformer, with at least temporarily a phase operating angle being provided and a switch-off of said load being provided in the zero passage of the driving mains alternating voltage, with a switch-off-reset impulse being applied to said inductive load following switch-off thereof from the alternating current mains, characterized in that said switch-off-reset impulse (13) is provided within the voltage halfwave following the switch-off moment in time or a subsequent voltage halfwave in-phase thereto for a predetermined period of time within one of said halfwaves and that said switch-off-reset impulse is dimensioned with regard to its voltage-time area in dependence on the amplitude or the voltage time area of the overshoot-voltage impulse (16) occurring following switching-off and is set proportionately larger, the smaller said overshoot voltage impulse is.
Dependencies are inferred from the claim text.