FIELD: electrical engineering; protecting three-phase motors against supply voltage unbalance. SUBSTANCE: device that functions to generate input and reference signals directly proportional to balanced components of forward and backward phase sequences has input-signal shaper and reference-signal shaper both connected to comparison gate and each incorporating three voltage-to-current converters. First voltage-to-current converters are made in the form of two seriesinterconnected capacitors inserted between first input and output of respective shaper, their connection point being connected to neutral bus through resistor. Second voltage-to-current converters are made in the form of three series-interconnected resistors inserted between second input and output of respective shaper, their connection point being connected to neutral bus through capacitors. Output of input-signal shaper is closed to neutral bus through diode connected in forward direction; first, second, and third inputs of reference-signal shaper are connected, respectively, to first, second, and third phases of supply mains and its output is connected to output of third voltage-to-current converter and closed to neutral bus through diode connected in backward direction to input of comparison gate through diode connected in forward direction. Equivalent conductance of first, second, and third voltage-to-current converters relate to one another as 
EFFECT: enhanced reliability of protection. 1 cl, 1 dwg
