92 results about "Residual flux" patented technology

To suppress the magnetizing inrush current occurring when supplying power of three phases of the transformer are performed simultaneously using three single-phase circuit breakers or a non-phase segregated operation-type circuit breaker, without providing a circuit breaker with a resistor or other equipment. A magnetizing inrush current suppression method for transformer suppresses a magnetizing inrush current occurring at the start of energizing of a three-phase transformer 300, when a three-phase power supply 100 is input to a terminal of each phase by means of a three-phase circuit breaker 200. In the method, by integrating phase voltages or line-to-line voltages on the primary side or the secondary side or the tertiary side when three-phase AC voltages are applied in a steady state to the transformer 300, steady-state magnetic flux 4, 5, 6 for each phase of the transformer is calculated, and the polarity and magnitude of the residual magnetic flux 7, 8, 9 of each phase of the transformer after the circuit breaker 200 shuts off the transformer are calculated, and the three-phase circuit breaker is caused to close simultaneously in a region 13 in which three phases overlap, each of the three phases having the polarity of the steady-state magnetic flux 4, 5, 6 equal to the polarity of the residual magnetic flux 7, 8, 9 for each phase of the transformer.

A system for reducing inrush current in a three phase utility transformer upon energization of the transformer by an applied three phase voltage utilizes a pre-flux circuit for establishing residual flux levels in the core segments of the primary windings of the transformer which are near the prospective flux levels established in the core segments by the applied voltage. The pre-flux circuit includes a pre-fluxing capacitor which, after being charged to a predetermined voltage level, is discharged serially through two of the primary windings to establish the predetermined flux levels in the core segments of the two windings, and a reduced flux level in the core segment of the remaining primary winding. The transformer is energized at the instant of positively-referenced peak phase voltage to the third primary winding such that prospective and residual flux approach a near-equal level in all three core segments and inrush current is reduced. The method may be applied to the secondary or tertiary windings instead of the primary windings. Additionally, an alternative method allows application of the pre-fluxing circuit to a delta-connected set of transformer windings.

A first calculation part calculates the phase-to-phase steady-state magnetic flux of the three phases of the power supply. A second calculation part calculates the phase-to-phase residual magnetic flux of the three phases in the primary windings side of the transformer when the circuit breakers interrupt the transformer. A phase detection part detects a voltage phase at which polarity and magnitude of the calculated steady-state magnetic flux and residual magnetic flux coincide. Closing control part firstly causes only the circuit breakers of the two phases to close at the detected voltage phase, and then causes the circuit breaker of the remaining one phase to close.

Disclosed is a compensated current differential relaying method and system for protecting a transformer more correctly by calculating and estimating an exciting current including a core-loss current and a magnetizing current, and, in particular, to a compensated current differential relaying method and system which can protect the transformer correctly irrespective of the level of remanent flux.

Inrush current suppression apparatus for suppressing a transformer inrush current including a transformer side voltage measurement unit which measures a voltage at a side of a transformer, a residual magnetic flux calculation unit which calculates three line-to-line residual magnetic fluxes, a power supply side voltage measurement unit which measures a voltage at a side of a power supply, a stable-state magnetic flux calculation unit which calculates three line-to-line stable-state magnetic fluxes, based on the voltage at the side of the power supply, a phase determination unit which determines a phase in which phases of the three line-to-line stable-state magnetic fluxes are respectively the same in polarity as phases of the three line-to-line residual magnetic fluxes, and a closing unit which closes the circuit breaker in the phase determined by the phase determination unit.

An optical device includes a Faraday rotator made of a bismuth substituted rare earth iron garnet single crystal (BIG) having a Faraday rotation of 45 degrees, and permanent magnets arranged beside the Faraday rotator to define two or more areas of a single domain structure in the Faraday rotator. Adjacent areas are magnetized in opposite directions to cause the polarization planes of light beams passing through the adjacent areas to rotate in opposite directions. The optical device satisfies the relation expressed by Hs / Br / DH>DeltaD / 2>0 where Hs (Oe) is a saturation magnetic field of the BIG, DH (cm<-1>) is a rate of change in magnetic field in the proximity to a boundary between the adjacent areas, Br (Gauss) is a residual flux density of the permanent magnets, and DeltaD is a distance between the two light beams.

This invention describes a method and an electrical circuit for controlling the closing of a three-phase circuit breaker with simultaneous pole operation to mitigate the inrush current resulting from power transformer energization by taking into account the residual magnetic flux in the transformer's magnetic core. It is disclosed a method to perform controlled switching on transformer and therefore mitigate the inrush current. It is disclosed that this method can be applied to any configuration of transformers which can be, but not limited to, Y-delta, Y-Y, delta-delta and delta-Y with either floating or grounded neutral.