Bi-stable Overload Relay with Single Coil Tripping
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Solution Overview
Problem
Existing overload relays require manual mode selection for operation, are complex, consume significant power, and lack 'trip free' functionality, making them inefficient and difficult to use both electromagnetically and manually.
Innovation Solution
A bi-stable overload relay design featuring an electromagnetic activation path with a single coil for both tripping and resetting, combined with a mechanical activation path for manual operation, which prevents manual resetting during electromagnetic tripping, allowing for efficient electromagnetic actuation with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single coil is used for both tripping and resetting operations, then device complexity and power consumption are reduced, but the ability to perform electromagnetic and manual actuation independently is compromised
Solution Approach 1:
The single coil is designed to perform dual functions: tripping and resetting. By controlling the polarity of the voltage applied to the coil, the same physical component can attract the armature (resetting) or release it (tripping), eliminating the need for separate coils while maintaining full operational versatility
Solution Approach 2:
The system dynamically switches between two operational modes using the same coil by reversing voltage polarity. This dynamic control allows the coil to serve different functions at different times, enabling both electromagnetic and manual actuation paths to work independently without requiring separate physical components
2Ease of operation
If the relay allows manual resetting at all times, then ease of operation is improved, but trip free functionality is lost when electromagnetic tripping is activated
Solution Approach 1:
When electromagnetic tripping is activated, the system preemptively prevents manual resetting by using the energized coil to maintain magnetic attraction on the armature. This preliminary anti-action blocks the mechanical reset path before it can interfere with the tripped state, ensuring trip free functionality while still allowing manual operation during normal conditions
Solution Approach 2:
The coil acts as an intermediary that mediates between manual and electromagnetic actuation paths. When energized for tripping, it overrides manual reset attempts; when de-energized, it allows manual resetting. This intermediary control mechanism reconciles the conflict between ease of operation and trip free reliability
3Reliability
If the operator coil remains energized to maintain relay state, then operational reliability is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous energization, the system uses periodic or pulsed action. The coil is energized only momentarily during tripping or resetting operations, then de-energized. The mechanical bistable structure maintains the relay state without requiring continuous power, dramatically reducing energy consumption while preserving reliability
Solution Approach 2:
The mechanical structure with spring and magnet provides self-latching functionality that maintains the relay state without external power. Once the coil actuates the armature to a new state, the mechanical elements hold that state automatically, making the system self-sustaining and eliminating the need for continuous coil energization
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
Enables easy, efficient, and power-efficient operation without the need for mode selection, ensuring the relay remains 'trip free' and reduces energy usage by de-energizing the operator coil when necessary, facilitating both electromagnetic and manual actuation.
Implementation Method 1
a magnet to hold the armature in the set state
Implementation Method 2
a coil to overcome the magnet to release the armature to the tripped state
Implementation Method 3
under the influence of a spring
Data Source
AI summary
An overload relay is disclosed in which a single operator coil is controlled for both tripping and resetting. A permanent magnet and a spring make the device bi-stable, so the coil may be unpowered when in the trip and reset states. Energization of the coil overcomes the magnet to allow tripping, while energization in an opposite direction adds to the magnet force to reset the device. An electromagnetic activation path overrides a mechanical activation path for electromagnetic tripping despite attempted manual resetting. The device may be pulse width modulated to reduce power consumption.