Contactor Auxiliary Contact Layout for Normally Closed State Detection
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Solution Overview
Problem
Existing switching devices, particularly gas-filled contactors, struggle to reliably detect the fully open state, as conventional monitoring methods are either costly, require complex wiring, or suffer from interference and wear, failing to meet the IEC 60947 standard's requirements for 'normally closed' detection.
Innovation Solution
A switching device with auxiliary contacts arranged outside the switching chamber, a contact element movable with the movable contact, and a mechanical drive, allowing reliable detection of the 'normally closed' state without additional electronic components, magnetic interference, or arcing issues, by measuring electrical resistance between the auxiliary contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage measurement via main contacts is used for monitoring, then detection reliability is improved, but device complexity and cost increase due to additional high-voltage cables and insulation requirements
Solution Approach 1:
The monitoring function is segmented from the main switching circuit. Auxiliary contacts separate the monitoring signal path from the high-voltage main contacts, allowing voltage measurement without requiring additional high-voltage cable routing through the switching chamber.
Solution Approach 2:
Auxiliary contacts act as intermediaries that transfer the switching state information from the main contacts to the monitoring circuit. This mediator approach allows indirect monitoring without direct connection to high-voltage main contacts, reducing insulation and cable complexity requirements.
2Difficulty of detecting and measuring
If microswitch is mounted inside switching chamber for monitoring, then detection capability is improved, but arc quenching and insulation performance deteriorate
Solution Approach 1:
The monitoring contact (auxiliary contact) is extracted from the main switching chamber environment. By placing the auxiliary contact outside the switching chamber, the harmful arc effects are eliminated from the monitoring circuit while preserving the detection capability.
Solution Approach 2:
The auxiliary contact serves as an intermediary element that is mechanically linked to the switching bridge but electrically isolated from the high-voltage arc environment. This allows state detection without exposing monitoring components to arc damage.
3Difficulty of detecting and measuring
If microswitch or auxiliary switch with supply lines is used for monitoring, then state detection is improved, but hermetic sealing capability deteriorates due to required cable penetrations
Solution Approach 1:
The auxiliary contacts serve multiple functions: they provide monitoring signals for state detection and simultaneously maintain the hermetic seal of the switching chamber. The non-magnetic material construction allows both monitoring capability and magnetic field shielding for hermetic sealing.
Solution Approach 2:
The auxiliary contacts are constructed from non-magnetic materials, changing the magnetic property parameter to enable hermetic sealing while maintaining electrical contact functionality for monitoring purposes.
4Loss of time
If monitoring contact changes state before main contact closes (leading design), then early detection is improved, but ability to detect intermediate states and blockages deteriorates
Solution Approach 1:
The auxiliary contact's movement is dynamically coordinated with the switching bridge through the mechanical connection. The auxiliary contact maintains contact with the switching bridge during overtravel, enabling continuous monitoring of intermediate states and blockages while still providing early detection capability.
Solution Approach 2:
The auxiliary contact is positioned and dimensioned to maintain contact during the overtravel phase, performing preliminary monitoring action that continues through intermediate states. This allows detection of blockages before the main contacts complete closure.
5Difficulty of detecting and measuring
If conventional microswitch is used for monitoring, then state detection is improved, but service life deteriorates due to limited switching cycle durability
Solution Approach 1:
The auxiliary contact creates a copy of the main contact's switching state through mechanical linkage. This copy contact operates in a lower-stress environment with reduced arcing, effectively extending the monitoring system's service life beyond what a direct microswitch implementation could achieve.
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 cost-effective, reliable detection of the fully open state, meeting IEC 60947 standard requirements, while maintaining hermetic sealing and avoiding interference, wear, and arcing problems.
Implementation Method 1
the movable contact (2) is in a through-connecting state, in which the movable contact (2) has mechanical contact with the at least one fixed contact (1) and is thus galvanically through-connecting to them
Implementation Method 2
the contact element (4) is arranged at a distance from the at least two auxiliary contacts (3) in a second switching state... by measuring electrical resistance between the auxiliary contacts
Data Source
AI summary
In an embodiment a switching device includes at least one fixed contact and a movable contact in a switching chamber, a contact element outside the switching chamber, a mechanical drive with a shaft, wherein the mechanical drive is configured for moving the movable contact and the contact element; and at least two auxiliary contacts outside the switching chamber on a side of the shaft facing away from the movable contact, wherein the contact element is configured to contact the at least two auxiliary contacts in a first switching state of the switching device and be spaced apart from the at least two auxiliary contacts in a second switching state of the switching device, or be spaced apart from the at least two auxiliary contacts in a first switching state of the switching device and contact the at least two auxiliary contacts in a second switching state of the switching device.