Rotary Switch Auxiliary Contact Sequencing for Arc Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing high current switches suffer from arcing damage between contacts during operation, leading to reduced lifespan and potential damage to electrical system components due to load dump, with existing solutions being unreliable and non-compliant with hazardous area codes.
Innovation Solution
A rotary switch design where auxiliary contacts break open before main contacts, utilizing a shaft with an auxiliary cam and main cam configuration to mechanically delay the breaking of main contacts, ensuring explosion-proof reliability and reducing arcing by controlling the sequence of contact opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple contacts open and close sequentially at different times, then arcing damage is reduced, but the first contact to make contact and/or the last contact to break experiences greatest contact wear and forms high-resistance connection
Solution Approach 1:
The switch is divided into two separate contactors: a main contactor for high-current switching and an auxiliary contactor for sequential operation. This segmentation allows the auxiliary contactor to handle the arcing and wear while the main contactor maintains reliable low-resistance connections for high current applications.
Solution Approach 2:
The auxiliary contactor acts as an intermediary between the control signal and the main contactor. It opens and closes sequentially before the main contacts, mediating the switching process to reduce arcing damage to the main contacts while maintaining their reliability for high-current applications.
2Object-affected harmful factors
If auxiliary contacts break before main contacts using electronic timing circuit, then break arc energy is minimized, but electronic timing circuits can fail and are non-compliant with hazardous area codes
Solution Approach 1:
The patent replaces the electronic timing circuit with a purely mechanical timing mechanism using cams and rollers. The auxiliary cam on the shaft mechanically delays the closing of auxiliary contacts relative to main contacts, eliminating electronic components while achieving the same sequential switching function for reduced arc energy.
Solution Approach 2:
The mechanical cam mechanism is self-regulating and inherently reliable without requiring external power or control circuits. The geometry of the cams and rollers automatically ensures the correct sequencing of contact operations, making the system compliant with hazardous area codes and eliminating points of failure associated with electronic timing circuits.
3Speed
If main contacts open first, then switching speed is faster, but load dump damages components connected to the battery
Solution Approach 1:
The auxiliary contactor performs a preliminary action by opening its contacts before the main contactor. This preliminary opening of the auxiliary circuit provides a path for residual current and ensures that the main contacts can open without causing load dump, protecting connected components while maintaining overall switching speed.
Data Source
AI summary
The present invention relates to a rotary switch. In particular, the rotary switch includes a main contactor having a main contact carrier and a main cam, a shaft rotatably journaled in the main contactor and extending axially through the main contactor, and an auxiliary contactor. When the switch is rotated from the ON position to the OFF position, the shaft rotates to break open auxiliary contacts before main contacts break open upon further rotation of the shaft.