FIELD: electricity.
SUBSTANCE: one controls the electric motor breaker position and records its switch-on point in the method of interturn short-circuit and rotor shift protection of electric motor. From this moment on, one keeps time ts, which is necessary for motor start, and constantly measures the magnetic fluxes sums from its first and second ends side. One compares the magnetic fluxes sum from the first end to the first protection operating value (reference standard), the magnetic fluxes sum from the second end - to the second reference standard, and these magnetic fluxes sums difference - to the third reference standard. Following of the end of the time ts, one switches the reference standards from the great one to the smaller in size. One constantly measures the power system bus voltage Ub of the electric motor and compares this voltage to the permissible voltage Uper simultaneously with the measurement of the magnetic fluxes sums from electric motor both ends and with the comparison of the sums difference among them to the relevant reference standards. In case of the exceedance of the magnetic fluxes sums or the difference among them of the relevant reference standards, one disconnects the electric motor. If the voltage is Ub≤Uper, then one keeps time tp, which is greater than the total protection operating time and the electric motor breaker opening, and switches the reference standards from the smaller ones to the greater ones in size. Once this is done, one keeps time tself, which is necessary for provision of the electric motor self-triggering, and switches the reference standards from the greater ones to the smaller ones in size at the end of this time. When the electric motor breaker opening by any cause, one switches the reference standards from the smaller ones to the greater ones in size.
EFFECT: enhancement of the sensitivity to the turn-to-turn short-circuit in the electric motor windings and to the rotor shifts along its direct axis.
2 dwg
