Method for diagnosing an operating state of an electrical switching device and electrical switching device for implementing such a method

An electrical switching apparatus configured to be coupled to an electrical conductor and comprising:

• separable contacts that are moved between an open position and a closed position by an electromagnetic actuator comprising a coil and a movable core that is attached to the separable contacts, the switching apparatus having a structure that limits the generation of eddy currents;
• a command circuit for controlling the voltage across the terminals of the coil, said voltage being referred to as the “coil voltage”, the command circuit comprising a device referred to as the “release” device, which may be selectively activated in order to make drop the electrical current flowing through the coil, which is referred to as the “coil current”, the coil voltage and the release device being activated or deactivated depending on the states of the command circuit;
• sensors for measuring the coil current and coil voltage;
• and
• an electronic control device that is configured to receive orders to open and close the switching apparatus, to receive the values of the measurements of coil current and coil voltage, and to control the states of the command circuit;
• wherein the switching apparatus comprises a contactor and is configured to diagnose an operating state of the switching apparatus, by implementing a diagnosing method comprising:
• a) receiving an order to close;
• b) commanding the electromagnetic actuator to close;
• c) measuring values of the coil voltage and coil current using the sensors and storing the values of the coil voltage and coil current;
• d) computing and storing values of a magnetic flux passing through the coil based on the stored values of the coil current and coil voltage and on values, which are stored beforehand in the electronic control device, of the resistance and inductance of the coil;
• and
• e) on the basis of the stored values of the magnetic flux and coil current, evaluating and storing positions of the core depending on a data table characteristic of the electromagnetic actuator, the data table defining a bijective relationship between the position of the core, the magnetic flux and the coil current,
• wherein computing values of the magnetic flux comprises an initial substep, referred to as the self-correction substep, followed by a computing substep, the self-correction substep comprising applying a current to the coil lower than a current referred to as the “start” current, keeping the movable core in the open position by a return member of the electromagnetic actuator, and evaluating and storing an initial value of the magnetic flux, said value being referred to as the “initial flux”, so that, when the coil current increases above the start current, the computation of the magnetic flux takes into account the value of the initial flux.