Verfahren und Vorrichtung zur Ansteuerung eines elektromagnetischen Schalters

A device (1) serves to switch on an electromagnetic switch (2) at the correct phase in order to close its contacts (3) at an ohmic load in the zero crossing of the a.c. supply voltage. The device is therefore provided with an ammeter to measure the current flowing through the solenoid (5) of the electromagnetic switch (2), a measuring instrument for measuring the closing instant of the contacts (3) and also measuring instruments (6, 7) for measuring the a.c. supply voltage zero crossings and the a.c. supply voltage amplitude. Furthermore, an evaluation device comprising process control (9) and connected to the measuring devices is provided for determining a switch-on instant of the electromagnetic switch for closing its contacts in the area of a zero crossing of the a.c. supply voltage. The information coming from the measuring instruments is thus processed accordingly. In an adjustment phase, suitable switch-on instants are determined and stored for closing the contacts in the zero cr ossing in the event of different operating parameters. The stored data are then available later during the operating phase so that the electromagnetic switch (2) can close its contacts (3) during the zero crossing of the a.c. supply voltage under changing operating conditions. If the closing instant of the contacts exceed a presettable tolerance from the zero crossing of the a.c. supply voltage during the operating phase, ...