DEFROSTING SYSTEM SUCH AS THAT FOR FREEZER Russian patent published in 2003 - IPC

FIELD: automatic-control devices for periodic turn-on of ac final control elements such as those for defrosting systems of freezers. SUBSTANCE: defrosting system has power supply, elapsed-time meter, heater, end-of-defrosting sensor, compressor, and three-contact electromagnetic relay whose movable contact is connected to second pole of power supply. Common lead of elapsed-time meter is connected to first fixed contact of three-contact electromagnetic relay and through compressor, to first pole of power supply. Defrosting system is provided in addition with adjustable-frequency pulse generator and flip-flop whose setting input is connected to elapsed-time meter output. Flip-flop output is connected to control coil of three-contact electromagnetic relay and to control input of adjustable-frequency pulse generator; synchronization input of the latter is connected to second fixed contact of three-contact electromagnetic relay. Flip-flop reset input is connected to junction point of end-of-defrosting sensor and heater; other lead of the latter is connected to second fixed contact of three-contact electromagnetic relay; second lead of end-of-defrosting sensor is connected to first pole of power supply. Common lead of flip-flop and that of adjustable-speed pulse generator are connected to common lead of elapsed-time meter whose complementing input is connected to output of adjustable-speed pulse generator. EFFECT: reduced power requirement, enhance performance characteristics of freezer such as its economic efficiency and service life. 1 cl, 1 dwg