Dual-Mode Transfer Switches for Fast and Reliable Load Transfer
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Solution Overview
Problem
Static transfer switches (STS) face failures that prevent load transfers from the primary power source to the alternate power source under certain conditions, leading to undesirable outcomes when the primary power source fails or is deemed unacceptable.
Innovation Solution
A transfer switch that operates in both static transfer switch (STS) mode and automatic transfer switch (ATS) mode, utilizing contactors and power stages to ensure reliable load transfer by switching between modes based on trigger conditions, allowing for faster transfer times in STS mode and slower but reliable transfer in ATS mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If static transfer switch (STS) mode is used to achieve fast load transfer, then transfer speed is improved, but reliability deteriorates due to power stage failures under certain conditions
Solution Approach 1:
The transfer switch dynamically switches between STS mode and ATS mode based on detected trigger conditions. When operating in STS mode, the system achieves fast transfer speeds using solid-state power stages. When a trigger condition indicates potential failure (such as abnormal current, voltage, or temperature), the system automatically transitions to ATS mode using contactors, which provides reliable load transfer even though it is slower. This dynamic adaptation resolves the contradiction by selecting the appropriate transfer mode based on real-time system state.
Solution Approach 2:
The system changes operational parameters by switching between two distinct transfer modes with different characteristics. STS mode uses solid-state power stages for rapid switching, while ATS mode uses electromechanical contactors for reliable isolation. The controller monitors system parameters and triggers mode switching when parameters indicate potential failure conditions, thereby maintaining both speed and reliability across different operating conditions.
2Reliability
If automatic transfer switch (ATS) mode is used to ensure reliable load transfer, then reliability is improved, but transfer speed deteriorates requiring multiple line cycles
Solution Approach 1:
The system dynamically selects between ATS mode and STS mode based on real-time monitoring of trigger conditions. During normal operation, the system may use STS mode for fast transfers. When trigger conditions indicate potential power stage failures (such as abnormal electrical parameters or thermal conditions), the system automatically switches to ATS mode, which uses contactors to provide mechanically isolated, reliable load transfer. This dynamic selection ensures reliability when needed while maintaining speed during normal conditions.
Solution Approach 2:
The controller continuously monitors system parameters and detects trigger conditions in advance of actual failures. When abnormal conditions are detected (such as excessive current, voltage deviations, or temperature rises), the system proactively switches from STS mode to ATS mode before a failure occurs. This preliminary detection and mode switching prevents reliability issues while minimizing the time spent in the slower ATS mode.
3Reliability
If dual mode operation is implemented to resolve reliability issues, then reliability is improved, but device complexity increases
Solution Approach 1:
The transfer switch is designed with multi-functionality by integrating both STS and ATS transfer modes within a single device. The system includes both solid-state power stages and electromechanical contactors, allowing it to perform both rapid solid-state switching and reliable mechanical isolation. This universal design enables the single device to handle both normal fast transfers and abnormal reliable transfers, improving reliability without requiring separate systems.
Solution Approach 2:
The patent merges two previously separate transfer switch technologies (STS and ATS) into a single hybrid system. The controller integrates monitoring of trigger conditions and automatic switching between modes, combining the fast transfer capability of STS with the reliable isolation of ATS. This merging reduces overall system complexity compared to having separate systems while maintaining the reliability benefits of dual-mode operation.
Data Source
AI summary
In one aspect, a transfer switch configured to operate in different transfer modes is provided. The transfer switch includes first and second inputs, first and second contactors, an output, first and second power stages, and a controller. The first and second inputs are configured to couple with first and second power sources, respectively. The first and second contactors are configured to selectively couple with the first and second inputs, respectively. The output is configured to couple with a load. The first and second power stages are configured to conduct electrical power when active. The controller is configured to determine whether a trigger condition has occurred while the first power stage is active, and in response thereto, to open the first contactor and activate the second power stage to transfer the load from the first power source to the second power source.