Patent ID: 6985345

Claim:
A method of operation of an electro-magnet connected to an intrinsically safe direct current circuit of an underground electro-hydraulic installation, controlled to switch backward and forwards between two switching positions for the operation of the closing body of a hydraulic valve in the underground installation, whereby, by means of an electronic control unit an exciting current is fed to the coil winding of the electro-magnet in the pull-in phase of the armature of the electro-magnet and in the retaining phase of the armature a retaining current which is relatively lower than the exciting current is fed in, in which the actual current in the coil winding following the actuation of the electro-magnet is continuously measured and evaluated to detect the movement of the armature, and is used as a control value for the reduction of the current fed to the retaining current level, and in the retaining phase the current fed is kept to the lower retaining current level by pulsed control.