GEAR FOR COMBINED PROTECTION OF THREE-PHASE LOADS Russian patent published in 1997 - IPC

FIELD: electrical engineering, protective gears pf three-phase symmetric (asynchronous motors) and asymmetric loads. SUBSTANCE: gear includes actuating organ 34 and actuating element 33, pickup manufactured in the form of current transformers 12 with resistive loads 3,4, three voltage dividers 11, 26, 20, comparator 14 and release 27 which acts under emergency condition on actuating mechanism and actuating organ 34 creating overload characteristic (i. e. dependence of overload time on its multiplicity) of hyperbolic type. Comparator and release can be made on discrete elements of digital logic. Additional source with button placed into circuit of third key 36 controlling second key 32 and actuating element 33 is used for unlocking. EFFECT: expanded functional capabilities and increased reliability of protection gear. 3 cl, 1 dwg