Rail Vehicle Power Supply Assembly Using Medium-Frequency Transformers
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Solution Overview
Problem
Existing electrical power supply arrangements for rail vehicles are heavy due to the need for large input transformers, especially at frequencies like 16.7 Hz, and require additional weight with DC/DC converters for operating on different DC voltage networks, limiting their versatility and efficiency.
Innovation Solution
A power supply arrangement using a rectifier configuration without galvanic isolation, converting AC voltage to medium-frequency AC, which allows transformers to be operated at higher frequencies, reducing size and weight, and utilizing transformers and converters as DC/DC converters to support operation on both AC and DC voltage networks with varying nominal voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an input transformer is used to transform high AC voltage to lower AC voltage, then the voltage transformation function is achieved, but the weight of the power supply arrangement increases significantly
Solution Approach 1:
The patent changes the operating frequency parameter of the transformer from standard mains frequency (50/60 Hz) to medium frequency (400 Hz). This parameter change allows the transformer to achieve the same voltage transformation ratio with significantly reduced core size and weight, while maintaining adequate magnetic flux density for efficient operation.
Solution Approach 2:
The patent introduces periodic switching action through pulse-width modulation (PWM) control of the inverter stage. By switching the DC voltage on and off at medium frequency and controlling the duty cycle, the system periodically transfers energy to the transformer, enabling voltage transformation without requiring a heavy continuous-duty transformer designed for low-frequency operation.
2Adaptability or versatility
If a DC/DC converter is added to enable operation on different DC voltage networks, then the adaptability to different voltage networks is improved, but the weight of the power supply arrangement increases
Solution Approach 1:
The patent designs the power supply arrangement with universal input capability that can accept both AC voltage networks (with or without rectifier) and DC voltage networks (with or without DC/DC converter) as input sources. The medium-frequency transformer and inverter stage serve multiple functions: voltage transformation from AC, voltage regulation from DC, and isolation for both input types, eliminating the need for separate dedicated circuits for each input type.
Solution Approach 2:
The patent implements dynamic switching capability where the system can automatically or manually switch between different operating modes (AC input with rectifier, AC input without rectifier, DC input with DC/DC converter, DC input without DC/DC converter) based on the detected input voltage type and magnitude. This dynamic adaptability allows a single lightweight power supply design to replace multiple fixed-design units.
3Device complexity
If the rectifier is connected without galvanic isolation, then the device complexity is reduced, but the safety and isolation performance deteriorate
Solution Approach 1:
The patent introduces the medium-frequency transformer as an intermediary component between the rectifier output and the inverter input. This transformer provides galvanic isolation, blocking harmful voltage transients, ground loops, and electrical noise from propagating through the system, while still allowing efficient magnetic coupling of the medium-frequency energy for voltage transformation and regulation.
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 solution achieves a significantly lower weight power supply arrangement that can efficiently operate on both AC and DC voltage networks with different nominal voltages, eliminating the need for heavy transformers and additional DC/DC converters, thereby enhancing operational flexibility and reducing weight.
Implementation Method 1
via an inverter which is connected to a primary side of a transformer
Implementation Method 2
a transformer with a secondary side which is connected to a second rectifier
Implementation Method 3
the secondary side of which is connected to a second rectifier
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electric interface is connected to power supply (A) and direct current (DC) voltage side of rectifier (181) of module (M1). The primary sides of transformers (171,172) of modules (M1,M2) are connected directly by electric interface and indirectly through inverter (161,162). The DC side of rectifier (182) of module (M2) is connected with electric terminal for connecting arrangement to intermediate circuit (ZK) so that power for operating driving motor (12) is transmitted from electric power supply network through rectifiers and inverters in intermediate circuit. Independent claims are included for the following: (1) method for operating rail vehicle; and (2) method for manufacturing electric power supply arrangement.