Hybrid Relay Switching With Air-Gap Arc Suppression
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Solution Overview
Problem
Existing hybrid relays used in energy management systems fail to comply with government regulations due to the absence of an air gap in the current path when in the off state, leading to rapid contact erosion and failure from arcing.
Innovation Solution
A hybrid relay design incorporating a semiconductor switch in parallel with a relay, controlled by a controller to create an air gap during switching, ensuring compliance with regulations by preventing arcing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard relay is used with electro-mechanical contacts, then the relay creates an air gap when off state is achieved, but arc formation occurs during switching which causes rapid contact erosion and relay failure
Solution Approach 1:
A semiconductor switch is introduced as an intermediary device between the power source and the relay contacts. The semiconductor switch conducts current during the switching transition period, preventing arc formation at the contacts. Once the contacts are fully closed or opened, the semiconductor switch turns off, allowing the relay to maintain its normal off-state air gap functionality.
Solution Approach 2:
The semiconductor switch is activated in advance before the relay contacts begin to move during switching operations. This preliminary action ensures that the contacts are never exposed to full voltage during movement, eliminating the conditions necessary for arc formation and contact erosion.
2Reliability
If a hybrid relay with a semiconductor switch is used to prevent arcing, then contact erosion is reduced and relay lifespan is extended, but the semiconductor switch forms a bridge across the contact air gap preventing compliance with government regulations
Solution Approach 1:
The relay system is segmented into two distinct operational modes: a transition mode where the semiconductor switch is active and prevents arcing, and a steady-state mode where the semiconductor switch is inactive and the relay contacts form a complete air gap. This segmentation allows the system to achieve both arc-free operation during switching and regulatory compliance during the off state.
Solution Approach 2:
The semiconductor switch operates periodically only during the brief transition periods when contacts are moving, rather than continuously. This periodic activation allows the relay to maintain a permanent air gap in the off state for regulatory compliance, while still providing arc protection during the critical switching moments.
3Reliability
If the semiconductor switch remains active to prevent arcing, then contact wear is minimized, but the relay cannot maintain an air gap in the current path during the off state
Solution Approach 1:
The semiconductor switch's operational state is dynamically adjusted based on the relay's operational phase. The switch is activated only during the dynamic transition period when contacts are moving and deactivated when the relay is in steady state. This dynamic control allows the system to maintain an air gap shape during the off state while still providing arc protection during switching.
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 design extends relay life by preventing arcing, thus complying with energy management system regulations and reducing contact wear.
Implementation Method 1
A hybrid relay comprises a semiconductor switch (e.g., MOSFET or TRIAC) that is coupled across the contacts of the relay. The semiconductor switch is activated (i.e., conducts) just before the relay contacts are opened or closed and continues to conduct until the contacts are fully open or fully closed.
Implementation Method 2
When the contacts are open, an air gap is formed and current does not flow through the relay, i.e., the off state.
Data Source
AI summary
Apparatus forming an arc-free hybrid relay having an air gap when in the off state. The apparatus comprises a first relay coupled to a second relay, and having a semiconductor switch arranged to temporarily shunt current around the second relay.