SHORT CIRCUIT PROTECTION DEVICE FOR ELECTRIC MOTORS Russian patent published in 2015 - IPC H02H7/00 

FIELD: electricity.

SUBSTANCE: device contains the first, second and third current relays which are respectively connected to secondary windings of the first and second, third and fourth, fifth and sixth current transformers. The first, third and fifth current transformers by primary windings are connected to splitting of A, B, C phases of the electric motor from input. The second, fourth and sixth current transformers are connected by primary windings to splitting of A, B, C phases of the electric motor from the side of its zero terminals. The executive element the output of which is connected to a switch disconnection circuit is connected to the first, second and third current relays. The first current-voltage converter assembly is connected to the first, third, fifth current transformers. The mini-selector is connected to the first current converter assembly. The first, second, third comparators are connected to the mini-selector and to the respective output of the first current converter assembly. The first, second, third, fifth, sixth and seventh AND gates are connected to the first and second, second and third, first and third, fourth and fifth, fifth and sixth, fourth and sixth comparators respectively. The first OR gate is connected to the first, second and third AND gates. The fourth AND gate is connected by the input to the first OR gate, and by the output it is connected to the executive element. The second current-voltage converter assembly is connected to the second, fourth, sixth current transformers. The maxi-selector is connected to the second current-voltage converter assembly. The forth, fifth, sixth comparators are connected to the maxi-selector and to the respective output of the second current-voltage converter assembly. The second OR gate is connected by inputs to the fifth, sixth and seventh AND gates, and by the output is connected to the fourth AND gate.

EFFECT: improvement of sensitivity of the device at two-phase short circuits.

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