DRY-RUNNING PROTECTIVE DEVICE FOR SUBMERSIBLE PUMP-UNIT MOTOR Russian patent published in 2002 - IPC

FIELD: electrical engineering; emergency protection of submersible pump-motor units. SUBSTANCE: device designed for protecting motor of submersible pump-motor unit against running in absence of water in well has dry-running sensor with make contacts, DC relay whose first pair of break contacts is inserted in magnetic-starter coil power circuit, step-down transformer, and rectifier bridge; DC relay control circuit is connected to rectifier bridge output; connected in parallel with rectifier bridge input is circuit of series- connected second pair of DC relay break contacts and dry-running sensor make contacts; rectifier bridge input is connected through dropping resistor to secondary winding of step-down transformer whose primary winding is connected to supply mains. EFFECT: enhanced reliability and repairability, simplified design. 2 cl, 1 dwg