Method of eliminating three-phase transformer trigger current and device for magnetizing core of the three-phase transformer with direct current

摘要

The present invention relates to a method of eliminating three-phase transformer (2) trigger current when connecting thereof to a three-phase alternating current source (4). Prior connecting to the three-phase alternating current source (4), direct current of a direct current source (16) is applied to one winding of the three-phase transformer (2) wherein said direct current source (16) is connected in one branch of a circuit of a device (1) for magnetizing the three-phase transformer (2) core. Said direct current magnetizes the three-phase transformer (2) core to thereby creating therein a flux of magnetic induction of a predetermined value. The three-phase transformer (2) is connected to the three-phase alternating current source (4) at an instant when the phase angle of the three-phase alternating current source (4) voltage achieves the predetermined value. After connecting to the three-phase alternating current source (4), the three-phase transformer (2) with magnetized core is disconnected from the direct current source (16) by opening the circuit of the device (1) for magnetizing the three-phase transformer (2) core with direct current. The invention also relates to a device for magnetizing core of a three-phase transformer (2) with direct current, which device comprises thee mutually connected branches from which each is connected or provided with means for connection with a coil (21, 22, 23, 24, 25, 26) of the same winding of the three-phase transformer (2). One branch of the device (1) comprises a direct current source (16) connected via a series connected transistor (14), a commutator choke coil (13) and a pair of diodes (121, 122) and resistors (111, 112) to the remaining two branches.