DEVICE TO PROTECT ELECTRIC MOTORS Russian patent published in 2003 - IPC

FIELD: electrical engineering, protection of electric motors against drop of network voltage. SUBSTANCE: proposed device has first, second and third terminals for connection of three-phase network and group of terminals for connection of phases of motor, first and second fuses, cut-on relay with group of make contacts and auxiliary make contact, first, second and third current relays with break contacts and switch with first and second make contacts, control relay with make contact with time delay for breaking, first, second, third and fourth diodes connected in bridge circuit in which diagonal control relay is placed, three-phase switch with group of make contacts and first and second additional make contacts. Input terminals of group of make contacts of three-phase switch are connected to terminals for connection of three-phase network and output terminals are coupled to input terminals of measurement networks of first, second and third current relays mentioned above correspondingly. EFFECT: widened functional capabilities of device thanks to provision for protection of electric motors against drop of network voltage. 1 dwg