44results about How to "Suppresses inrush current" patented technology

The invention discloses a phase selection control method aimed at a zero-load transformer comprising a primary side employing star ungrounded connection and calculating the influence of residual magnetism of the zero-load transformer. A vacuum breaker, a current zero crossing detection circuit, a voltage zero crossing detection circuit and a control circuit are included. The method is characterized in that (a) when the breaker is opened, a phase B of the breaker is firstly disconnected when a current of the phase B crosses zero, then currents flowing through a phase A winding and a phase C winding of the transformer are of the same size and opposite directions, and when the two currents cross zero, a phase A and a phase C of the breaker are disconnected simultaneously, and phase angles of voltages of the two phases at the moment of disconnection are recorded; and (b) when the breaker is closed, the phase A and the phase C of the breaker are closed at the same time if the voltage phase angles of the two phases equal the voltage phase angles of last breaker opening, and the phase B of the breaker is closed when the voltage of the phase B reaches a peak value. The method can effectively inhibit inrush current of a closing moment of the zero-load transformer.