Transformer Coil Group Energizing to Limit Inrush Current
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Solution Overview
Problem
Transformers, especially those in electric railway propulsion vehicles, experience transient high inrush currents when energized, leading to potential disconnection by protection installations and increased complexity and cost in existing solutions.
Innovation Solution
The method involves supplying a supply voltage to a first number of groups of coils for a predetermined time to limit inrush current, followed by supplying the voltage to all groups of coils, eliminating the need for complex pre-magnetizing circuits and phase synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an air gap is introduced into the magnetic core to limit inrush current, then the inrush current is reduced, but the device complexity and manufacturing cost increase
Solution Approach 1:
The primary winding is divided into multiple coil groups that can be independently connected or disconnected. This segmentation allows selective energization of coil groups to control inrush current without modifying the magnetic core structure, thereby resolving the contradiction between current limitation and structural simplicity.
Solution Approach 2:
The invention changes the electrical connection parameters (series/parallel configuration) of the coil groups rather than modifying the magnetic core's physical structure. By adjusting the number of active coil groups and their connection mode, the effective impedance changes dynamically, limiting inrush current while maintaining a simple standard stacked core structure.
2Object-generated harmful factors
If phase synchronization is implemented to limit inrush current, then the inrush current is reduced, but the device complexity and cost increase
Solution Approach 1:
The controller pre-configures the switching states of coil groups before full energization occurs. By selectively connecting or disconnecting specific coil groups in advance based on their impedance characteristics, the system prepares an optimal configuration that limits inrush current without requiring real-time phase synchronization or complex control algorithms.
Solution Approach 2:
The controller automatically determines the optimal switching configuration based on the transformer's own operational state and coil group characteristics, without requiring external synchronization signals or complex coordination with the power supply phase. The system self-regulates to achieve inrush current limitation.
3Power
If multiple coil groups are connected in parallel to increase power capacity, then the transformer power handling increases, but the inrush current increases
Solution Approach 1:
The invention dynamically adjusts the connection configuration of coil groups during the energization process. Initially, coil groups are connected in a configuration that limits inrush current (e.g., series connection or selective disconnection), and then the configuration is changed to parallel connection for full power operation. This dynamic reconfiguration resolves the contradiction between power capacity and inrush current.
Solution Approach 2:
Before full parallel connection of all coil groups, the controller preliminarily energizes a subset of coil groups or configures them in a high-impedance state. This preliminary action builds up magnetic flux gradually, preventing excessive inrush current when the full parallel configuration is eventually activated, thus enabling both high power capacity and controlled inrush current.
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
This approach reliably limits inrush current to a non-excessive amount, preventing erroneous activation of protection devices and simplifying the energizing process without the need for complex auxiliary circuits or phase synchronization.
Implementation Method 1
By supplying the supply voltage to the first number of the groups of coils, a common magnetic flux is passed through the groups of coils
Implementation Method 2
a transient high inrush current flows upon connection of the transformer to a supply voltage when the transformer is in an unenergized, or unmagnetized, state. The high inrush current flows as a result from a magnetic saturation in the transformer core
Data Source
Figure 1
AI summary
Transformer connection assembly comprises a transformer having groups (5a, 5b) of coils forming primary transformer windings (5), and a secondary transformer winding (6), the groups (5a, 5b) in an operational state of the transformer being passed through by common magnetic flux; a first switch (3), when closed, connects supply voltage terminal (2) to first number (5a) of groups of coils; a second switch (4), when closed, connects supply voltage terminal (2) to entirety (5a, 5b) of groups of coils; and an energizing controller configured to perform a method comprising, in this time order: supplying supply voltage to first number (5a) of groups (5a, 5b) of coils for predetermined amount of time, the first number (5a) being less than the entirety of groups (5a, 5b) of coils, thereby passing a common magnetic flux through the groups (5a, 5b) of coils; and supplying supply voltage to the entirety of the groups (5a, 5b) of coils.