METHOD FOR PROTECTING ELECTRIC INSTALLATIONS AGAINST OVERHEAT Russian patent published in 2012 - IPC H02H5/04 

FIELD: electricity.

SUBSTANCE: device has a closed magnetic circuit designed in the manner of a magnetic amplifier and consists of three rods. The two lateral rods contain power windings connected to the load in an accident-serial and serial way. One rod has magnetisation winding. A ferromagnetic insert is introduced with second-order phase transition temperature whereat the material loses its magnetic properties if heated, recovering them to the initial level when cooled. The ferromagnetic insert is equipped with a heating element having winding connected to the load in a serial way. If current is supplied in the control winding the magnetic conductor saturation occurs. Because of low resistance of the operating windings connected to the load in a serial way, alternating voltage applied to such windings, almost the whole of the voltage falls to the load. During the insert heating magnetic resistance in the middle rod sharply increases. The magnetic conductor remains unsaturated. As a result, the operating windings reactive resistance sharply increases, the value of current in the load circuit decreasing. When cooled, the insert recovers its initial magnetic properties, the load current increasing.

EFFECT: ensuring electric energy consumers protection against thermal overload without breaking the control circuit contacts.

4 cl, 3 dwg