Research on Phase Separation Input Strategy of Triangle Connection Asynchronous Motor

When the mine triangular connected asynchronous motor is put into the power grid with the vacuum circuit breaker, the voltage of the power grid decreases and the transient current becomes too large, which destroys the insulation strength of the motor. In order to solve this problem, this paper proposes a control strategy of using the permanent magnet vacuum circuit breaker to phase-separate and put the triangular connected asynchronous motor into the power grid. Under the condition of zero rotational speed, the mathematical model of two-phase asymmetry and three-phase symmetry of the asynchronous motor in the process of putting into power grid is established. The time domain expression of the stator current and the closing phase is determined and the influences of different closing phases on the stator current are analyzed. Combined with the motor parameters, the optimal phase of each phase of the motor is deduced. The simulation results show that in the optimal closing phase, the phases B and C are put into the power grid at the same time and then the phase A into the power grid. Under this condition, the starting current of the motor is reduced by 38.65% compared with that under the three phases at the same time. In the condition of the maximum fluctuation of the actual closing inherent time error, the starting current is reduced by 30.65%. This indicates that using the permanent magnet vacuum circuit breaker to put the motor into the power grid with phase separation will well suppress the transient impact current generated by the motor starting.