Abstract: Using a switching circuit (2) for a reactive power compensation device (1), he compensation capacitors of the reactive power compensation device (1) can be switched on with voltage measuring devices (30, 31) which are switched between two phase conductors (3, 4) if the the voltage is the same on both sides of an open phase conductor switch (24). In a preferred embodiment, closing the second phase conductor switch (25) occurs triggered by a delay device (36) following a fixed delay time. In another preferred embodiment, switching on occurs when the voltage is the same between the phase conductors (4,5) on both sides of the second phase conductor switch (25), whereas this condition can be checked with two other voltage measuring devices switched between the phase conductors (4, 5) as well as with another equivalence comparator.

Abstract: A method for reduction of switch-on surges while operating an inductive rry current load is described, having a magnetizable core and three windings arranged in different connection patterns to a rotary current alternating network. A phase angle control unit provides at least a temporary phase operation of the voltages between the lines of the windings. The arrangement includes core sectors allocated to a winding being brought to pre-determined state of magnetization, at least two of three voltages between the lines of the windings having unipolar voltage halfwaves reduces to at least half their voltage-time surface being connected successively to the rotary current load according to the present phase shift of the voltages between the lines.

Abstract: A method and apparatus for avoidance of power-up current surge upon activation of a current supply device under inductive effect. An alternating-current switch is connected in series with the current supply device and a phase cut-in circuit is provided for enabling adjustable connection of the current supply device with the mains alternating voltage starting with the instant of powering up with equal-size unipolar phase segments. A switching unit is provided for activation of the phase cut-in circuit so that a predetermined number of the equal-size unipolar segments can be produced. An oppositely poled half wave which follows in time immediately is switched with an ignition signal of 170 to 180 degrees. In the phase cut-in circuit, respectively, an ignition signal is produced at the predetermined phase cut-in angle in the half waves following this half wave.

Abstract: A transformer is energized from an a.c. source by initially applying the . voltage to the transformer during small but progressively increasing fractions of a succession of initial half-cycles. This is continued until the rated voltage is achieved or until the reactive current exceeds a predetermined value below that which would cause tripping of the transformer. In the event that the reactive current reaches the predetermined value, the remanence of the transformer is set at a selected level by applying the a.c. voltage to the transformer during an additional half-cycle. The length of exposure of the transformer to the a.c. voltage during the additional half-cycle depends upon the circumstances. Once the remanence has been set, operation of the transformer proceeds normally.

Abstract: A device runs a precheck of an inductive load for an overload prior to swhing on to supply mains. For this purpose, following switching-on for a load precheck, initially a phase limited voltage signal is applied to the load, whereby the voltage signal duration gradually increases. With the start of each application of voltage, the active current is measured in a narrow time window. If it does not exceed a predetermined active current limit at an application of a specific effective voltage, the load is switched to the mains. Otherwise, the switch-on process is cut off. This switching-on process avoids a high taxing of the mains in the event of a short circuit or an overload. The active current window begins with the application of voltage to the load. At a different time than this time window, a further measurement window is provided for the reactive current, whereby this measurement window begins with the zero crossing of the alternating voltage.

Abstract: 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.