Zero-Cross Relay Switching with Adaptive Arc Delay Control
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Solution Overview
Problem
Mechanical relays used in home appliances experience degradation due to plasmatic arcs when switching at random times relative to AC mains power, causing electromagnetic noise and reliability issues, which existing methods fail to address effectively.
Innovation Solution
A method and control unit that determine the control time instant for switching relays based on zero crossing detection of AC mains voltage, adjusting the control delay to align with zero crossing instants to minimize arc formation, using a detection circuit to monitor arc noise and update the control delay for precise zero cross control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the relay is switched at a random time instant relative to the AC mains power sine wave, then the switching operation is simple and fast, but the relay contacts and mechanical components are subjected to degradation from plasmatic arcs
Solution Approach 1:
The control unit determines the control time instant in advance by considering the control delay of the relay, so that the relay contacts are actually switched at the zero crossing time instant of the AC mains voltage. This preliminary timing adjustment prevents plasmatic arcs and extends relay life while maintaining efficient switching operation.
2Reliability
If the relay switching time is advanced to account for control delay, then the relay switches at zero crossing time instant, but the control timing becomes more complex
Solution Approach 1:
The control unit detects the actual switch-on or switch-off time instant of the relay and compares it with the desired zero crossing time instant. Based on this feedback, the control unit determines an updated control delay and adjusts future control time instants accordingly, enabling adaptive optimization of switching timing without requiring complex manual calibration.
Solution Approach 2:
The control unit automatically determines the control delay by detecting the actual relay switching behavior and self-adjusts the control time instant for subsequent operations. This self-service mechanism eliminates the need for external calibration or complex control logic, simplifying the overall system while maintaining precise zero-crossing switching.
3Reliability
If zero cross detection is used to avoid plasmatic arcs, then relay degradation is reduced, but the control system requires additional detection and timing mechanisms
Solution Approach 1:
The control unit combines the zero crossing detection function, control delay determination, and switching control into a single integrated device. By merging these functions, the patent avoids the need for separate detection circuits and timing mechanisms, reducing overall system complexity while achieving reliable zero-crossing switching and extended relay longevity.
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 reduces relay degradation by minimizing arc generation during switch-on and switch-off events, enhancing the reliability of home appliances by ensuring precise timing of relay operations.
Implementation Method 1
the coil current creating a magnetic field which attracts the movable anchor
Implementation Method 2
determining an upcoming or future zero crossing time instant of the AC voltage which is applied to the load ports of the relay
Implementation Method 3
the relay contacts and/or its mechanical components may be subjected to degradation resulting from plasmatic arcs which form between the relay contacts during switching events
Data Source
Figure 1~2a
Figure 2b~3a
Figure 3b
AI summary
A method (600) for controlling a relay (1) is described. The method (600) comprises applying (601), at a control time instant (313), a control signal to a control port (4) of the relay (1) for initiating a switch-off event or a switch-on event of the relay (1), wherein the control time instant (313) depends on a previously determined control delay (315) of the relay (1). The method (600) further comprises determining (602) arc information (406) regarding the formation of an arc between contacts (5) of the relay (1) during the switch- off event or the switch-on event of the relay (1), and updating (603) the control delay (315) based on the arc information (406).