Main Transformer Phase Synchronization for Inrush Current Prevention
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Solution Overview
Problem
Existing rolling stock systems experience excitation inrush currents when passing through switching or dead sections, or when attaching a pantograph to an overhead wire, leading to power failures and discomfort, and lack effective countermeasures for power outages, especially during overhead wire failures.
Innovation Solution
The system reversely excites the main transformer by detecting the voltage of the overhead wire using AC-DC power converters and power storage devices, ensuring the primary side matches the overhead wire's phase and voltage, and supplies power to auxiliary machines during wire failures using stored energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rolling stock passes through a switching section or dead section, or attaches a pantograph to an overhead wire, then power is supplied to the main transformer, but an excitation inrush current flows into the main transformer causing power failures and discomfort
Solution Approach 1:
The system performs preliminary detection of the overhead wire voltage phase using a detector before connection, and pre-excites the main transformer by applying a voltage at the detected phase through the AC-DC power converter. This preliminary action ensures that when the pantograph connects to the overhead wire, the transformer is already synchronized to the correct phase, preventing excitation inrush current from flowing into the transformer.
2Object-affected harmful factors
If conventional switching section control is used to prevent excitation inrush current, then the inrush current is prevented, but main circuit currents are temporarily restricted deteriorating riding comfort
Solution Approach 1:
The system uses the rolling stock's own AC-DC power converter and power storage device to perform the phase detection and pre-excitation operations, eliminating the need for external switching section equipment to control the inrush current. This self-service approach allows the main circuit currents to remain unrestricted while still preventing excitation inrush current, thereby maintaining riding comfort.
3Object-affected harmful factors
If a converter is installed in ground equipment to control the middle section phase, then excitation inrush current is prevented, but the size of the equipment increases
Solution Approach 1:
The system extracts the phase detection and pre-excitation functions from ground-based switching section equipment and relocates them to the rolling stock itself. By using the detector and AC-DC power converter already present in the rolling stock, the patent eliminates the need for additional ground equipment, thereby reducing overall system complexity and equipment size while still preventing excitation inrush current.
4Reliability
If the overhead wire experiences a power failure, then power supply to auxiliary machines is stopped, but no effective countermeasures exist to maintain operation
Solution Approach 1:
The system stores energy in advance in the power storage device (such as a capacitor or battery) connected to the AC-DC power converter. When a power failure of the overhead wire is detected by the detector, this pre-stored energy is immediately discharged to supply power to the auxiliary machines, maintaining their operation during the power failure without requiring any structural changes or additional countermeasures.
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
Prevents excitation inrush currents and ensures continuous power supply to auxiliary machines during overhead wire failures, enhancing riding comfort and reducing equipment capacity needs.
Implementation Method 1
an AC-DC power converter which performs a regeneration operation for converting an alternate current of the overhead wire to a direct current and returning an energy from a DC side to an AC side
Implementation Method 2
the main transformer is reversely excited such that a primary side of the main transformer has the same phase/same voltage as the detected voltage of the overhead wire
Data Source
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AI summary
A breaker 162 is opened when a pantograph 101 is lowered. The pantograph 101 is connected to an overhead wire 200. Voltage and its phase of the overhead wire are detected by a detector 161. Power is supplied from a power storage device 150c to a tertiary winding 112c via a power converter 14c such that a primary side of the main transformer 110 has the same voltage and phase as the overhead wire so as to reversely excite the main transformer 110. When the voltage of the main transformer 110 has the same phase as the voltage of the overhead wire 200, the breaker 162 is turned on and then the pantograph 101 is raised, to connect the overhead wire 200 and the main transformer 110 to each other, thereby preventing the occurrence of an excitation inrush current to the main transformer 110.