Magnetizing Inrush Current Suppression via Phase-Synchronized Closing
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Solution Overview
Problem
Existing methods fail to effectively suppress magnetizing inrush currents in transformers, especially when three phases are simultaneously closed, and are influenced by DC voltage and residual magnetic flux, leading to voltage fluctuations and inaccurate flux derivation.
Innovation Solution
A magnetizing inrush current suppression device that measures three-phase AC voltages and terminal voltages of a transformer, calculates prospective and residual magnetic fluxes, determines the minimum residual magnetic flux, and simultaneously closes the circuit-breaker at a specific phase position to minimize inrush currents, independent of neutral point voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a circuit-breaker with a resistor is used to suppress magnetizing inrush current, then the inrush current is suppressed, but the device size becomes large
Solution Approach 1:
The invention extracts and eliminates the resistor component from the circuit-breaker structure. By using a circuit-breaker without a resistor (contact-only structure), the device size is reduced while still achieving inrush current suppression through controlled closing timing based on voltage phase detection
Solution Approach 2:
The invention changes the operating parameter from using a resistor-based current limiting approach to a timing-based approach. By detecting the voltage phase angle and closing the circuit-breaker at specific timing (when voltage is near zero), the inrush current is suppressed without requiring additional resistive components
2Ease of operation
If three-phase simultaneous operation circuit-breaker is used, then the operation is simple, but the magnetizing inrush current cannot be suppressed
Solution Approach 1:
The invention introduces dynamic phase detection and timing control to the circuit-breaker operation. The control unit detects the instantaneous voltage phase angle and dynamically determines the closing timing for each phase, transforming the static simultaneous operation into a dynamic controlled operation that suppresses inrush current
Solution Approach 2:
The invention performs preliminary detection of the voltage phase angle before closing the circuit-breaker. By detecting the voltage waveform in advance and calculating the appropriate closing timing, the system prepares the optimal closing moment for each phase to minimize inrush current while maintaining simple operation
3Reliability
If DC voltage remains in transformer after interruption, then the voltage is present, but the residual magnetic flux cannot be precisely derived
Solution Approach 1:
The invention introduces an intermediary calculation process that separates the DC voltage component from the AC voltage component. By detecting the voltage phase angle and using trigonometric relationships, the system calculates the residual magnetic flux while eliminating the influence of DC voltage, achieving precise measurement despite DC presence
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device precisely suppresses magnetizing inrush currents and accurately determines residual magnetic fluxes, even with DC voltage present, by integrating line voltages and determining the optimal closing phase position, thereby stabilizing system voltage.
Implementation Method 1
a circuit-breaker that closes and opens connection between a transformer having a Y-connected primary winding and Δ-connected secondary winding and a three-phase AC power supply
Data Source
AI summary
According to one embodiment, there is provided a magnetizing inrush current suppression device. A closing phase determination unit determines a phase position for suppressing the magnetizing inrush current among phase positions in which the prospective magnetic flux calculated by the prospective magnetic flux calculation unit and the residual magnetic flux calculated by the residual magnetic flux calculation unit coincide between the lines of the minimum residual magnetic flux determined by the minimum residual magnetic flux determination unit, as a closing phase position. A closing unit simultaneously closes the three phases of the circuit-breaker at the determined closing phase position.