Bi-stable Relay Tamper Resistance via Magnetic Counteraction
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Solution Overview
Problem
Existing bi-stable relays used in electricity meters are vulnerable to magnetic tampering and fail to function reliably when exposed to strong magnetic fields, making it difficult for energy providers to remotely disconnect power supply to consumers.
Innovation Solution
A bi-stable relay design that combines a permanent magnet and an electromagnet to resist magnetic tampering, using a slider with a magnetically conducting armature and a spring arrangement to maintain stable positions, allowing the relay to withstand high currents and external magnetic fields, and enabling remote control through an electromagnet that counteracts the permanent magnet's flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a normal electromagnetic relay is used, then the relay can be controlled remotely, but the relay becomes vulnerable to magnetic tampering and may malfunction when exposed to strong magnetic fields
Solution Approach 1:
The patent combines a permanent magnet and an electromagnet in a bi-stable relay system. The permanent magnet provides a stable magnetic field that is resistant to external magnetic tampering, while the electromagnet enables controlled switching. This merging of two magnetic sources creates a system that maintains reliability under magnetic interference while preserving remote control capability through the electromagnet's controlled activation.
Solution Approach 2:
The relay employs a composite magnetic system using both permanent magnet material and electromagnet material. This composite approach creates a magnetic field structure where the permanent magnet's stable field counteracts external magnetic interference, while the electromagnet's field provides controlled actuation. The composite magnetic architecture ensures both tamper resistance and controllable operation.
2Power
If the relay is designed to handle high currents of at least 50 A, then the relay can be used for power line disconnection, but the electrical contact members experience repelling Lorentz forces that can force them out of contact
Solution Approach 1:
The patent applies the counterweight principle by using spring arrangements that exert a force opposing the repelling Lorentz forces generated during high current flow. The springs are pre-loaded to provide sufficient contact pressure that counteracts the electromagnetic repulsion between contact members, ensuring stable electrical contact even when carrying high currents of 50 A or more.
Solution Approach 2:
The spring arrangements are pre-loaded before current flow begins, establishing a preliminary contact force that will counteract the Lorentz repulsion when high current is applied. This preliminary mechanical force ensures that the contact members remain firmly pressed together even under the stress of high current operation.
3Reliability
If a bi-stable relay with permanent magnet is used to resist magnetic tampering, then the relay maintains stable states in strong magnetic fields, but additional magnetic flux must be managed to enable switching
Solution Approach 1:
The patent introduces magnetically conducting elements as intermediaries between the permanent magnet, electromagnet, and slider armature. These conducting elements channel and manage the magnetic flux from both the permanent magnet and electromagnet, facilitating controlled interaction between the two magnetic sources. The intermediary elements simplify flux management by providing dedicated magnetic pathways that guide the flux efficiently between components.
Solution Approach 2:
The magnetic circuit is segmented into distinct flux pathways using separate magnetically conducting elements for the permanent magnet and electromagnet. This segmentation allows independent management of each magnetic source's flux, making it easier to control the overall magnetic field behavior. The segmented approach enables the permanent magnet to provide stability while the electromagnet provides switching control without excessive magnetic interference between the two sources.
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 solution significantly reduces the risk of magnetic tampering, allowing the relay to maintain stable states even in strong magnetic fields and enabling reliable remote control of power supply, suitable for high-current applications and multi-phase meters.
Implementation Method 1
a permanent magnet arranged together with at least a first magnetically conducting element for generating a magnetic flux serving to magnetically attract the armature of the slider, so as to keep the slider in the second stable position
Implementation Method 2
an electromagnet comprising at least one electrical coil for receiving an electric input, wherein the electromagnet is arranged to magnetically attract said armature, via the first magnetically conductive element, in response to said electric input, so as to move the slider from the first to the second stable position
Implementation Method 3
the electromagnet is arranged to magnetically counteract the magnetic flux generated by the permanent magnet in response to said electric input, so as to allow the first spring arrangement to move the slider from the second to the first stable position
Implementation Method 4
a first spring arrangement arranged to provide a force on the slider, so as to keep the slider in the first stable position irrespective of the magnetic flux generated by the permanent magnet
Data Source
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AI summary
The invention provides a bi-stable electric relay. Electrical contact members CM1, CM2 are in contact with the respective electrical terminals T1, T2. The contact members CM1, CM2 provide electric contact in the first stable state, and are disconnected in the second stable state. A slider SL with a magnetically conducting armature AM can move between two stable positions and the slider SL can thereby break electrical contact between the contact members CM1, CM2 in one stable position. A permanent magnet PM arranged with a magnetically conducting element ML1, ML2 for generating a magnetic flux to magnetically attract the armature AM of the slider SL, so as to keep the slider SL in the stable position, where the contact members CM1, CM2 are disconnected. An electromagnet EM or solenoid, preferably sharing the magnetically conducting element ML1, ML2 with the permanent magnet PM, is used to switch between the stable states by being energized by an electric current to either attract the armature AM of the slider SL or to cancel the attraction force provided by the permanent magnet. The electromagnet EM should be powerful enough to counteract the magnetic attraction force of the permanent magnet PM in the disconnected state. The contact members CM1, CM2 are designed such that repelling Lorentz forces serve to force their electric contact points against each other, thereby allowing the relay to be used for high currents without damage problems. The relay can be integrated in an electricity meter to allow remote breaking of delivery of electric energy to a consumer.