Thyristor Bridge Filter for Excitation Systems
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Solution Overview
Problem
Conventional thyristor power converters for excitation applications are overly complex and costly due to excessive use of protective components, which increases material and labor costs while compromising reliability, especially when relying on active diode bridges like the bucket filter approach that stresses capacitors and introduces transient disturbances.
Innovation Solution
A three-phase AC line filter is used as the primary filtering method, eliminating RC snubbers and ferrites, and employing series resistive and capacitive elements across the input line with bleed resistors to absorb energy and protect thyristors, reducing component count and complexity, and providing reliable protection without active diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective components (RC snubbers, ferrites, AC line filters) are added to meet thyristor specifications, then reliability of thyristor operation is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts and eliminates unnecessary protective components from the conventional bridge circuit. By analyzing the actual operational requirements, the invention removes RC snubbers, ferrites, and complex AC line filters that were traditionally added but are not essential for reliable thyristor operation in excitation applications, thereby simplifying the circuit while maintaining reliability
Solution Approach 2:
The patent makes the thyristor bridge circuit universally applicable by designing it to inherently meet thyristor specifications without requiring additional protective components. The bridge circuit is designed with proper voltage and current distribution characteristics that naturally protect the thyristors, eliminating the need for application-specific protective additions
2Reliability
If multiple protective components are added to the bridge circuit, then component protection is improved, but material and labor costs increase
Solution Approach 1:
The patent removes expensive protective components such as RC snubber circuits, ferrite beads, and complex AC line filters from the design. By extracting these unnecessary elements, the invention significantly reduces both material costs and assembly labor while maintaining adequate component protection through the simplified bridge circuit design
Solution Approach 2:
The patent replaces expensive protective components with a more economical design approach. Instead of using costly RC snubbers and ferrites, the invention relies on the inherent characteristics of the simplified bridge circuit to protect components, achieving the same protective function at lower cost
3Reliability
If conservative design with extensive protective features is used, then reliability requirements are met, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates excessive protective features from conservative designs. By analyzing the actual reliability requirements of excitation systems, the invention removes redundant protective components while maintaining the necessary level of reliability through a simplified, more elegant circuit design
Solution Approach 2:
The patent changes the design parameters and operating characteristics of the bridge circuit to inherently provide the necessary protection and reliability. By optimizing voltage distribution, current sharing, and switching characteristics, the invention achieves reliable operation without relying on extensive protective additives
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 configuration reduces complexity, cost, and improves reliability by distributing energy across multiple capacitors, reducing stress on components, and eliminating the need for active diodes, resulting in lower failure rates and enhanced operational safety.
Implementation Method 1
circuits incorporating a series resistive element and a series capacitive element
Implementation Method 2
series resistive element and a series capacitive element
Implementation Method 3
employing series resistive and capacitive elements across the input line with bleed resistors to absorb energy
Data Source
AI summary
An exciter system for the field of a synchronous generator excitation is provided. The exciter system includes an AC power source; a three-phase thyristor bridge having six legs, the three-phase bridge being connectable with the AC power source, and being adapted to provide a variable DC voltage output; a thyristor in each of the six legs of the three-phase bridge, wherein the thyristors provide a path for a device current; and a three-phase AC line filter series, including series resistive and capacitive elements across each phase of the AC power source and a plurality of bleed resistors, wherein at least one bleed resistor is connected to each AC input connection of the filter.