Double Make Double Break Interrupter Module for MCCB Contact Wear
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Solution Overview
Problem
Molded case circuit breakers (MCCBs) experience uneven wear of electrical contacts due to short circuits, leading to reduced contact force and overtravel range on one side, affecting the circuit's reliability.
Innovation Solution
The introduction of a rotatable blade assembly with two independent conductive blades, each equipped with an extension spring and cam surfaces, allows for individual control of overtravel and contact force, ensuring balanced engagement of movable and stationary contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a unitary blade is used in the circuit breaker, then the structure is simple and manufacturing is easier, but uneven wear of electrical contacts occurs leading to reduced contact force and overtravel range
Solution Approach 1:
The unitary blade is divided into two separate conductive blades (first conductive blade and second conductive blade), each with its own movable electrical contact. This segmentation allows independent adjustment and maintenance of each blade's contact force and overtravel, preventing the uneven wear problem that occurs with a single unitary blade where one side's degradation affects the entire assembly.
2Device complexity
If a common drive mechanism is used for all poles, then the operation is synchronized and device complexity is reduced, but uneven erosion of contacts cannot be individually compensated
Solution Approach 1:
While maintaining a common drive mechanism for synchronized operation of all poles, the patent introduces local quality variations by equipping each conductive blade with its own extension spring and cam surface configuration. This allows each blade to have customized contact force and overtravel characteristics tailored to its specific wear condition, while still being driven by the common mechanism.
3Reliability
If extension springs are added to each conductive blade for independent control, then contact force and overtravel can be individually adjusted, but device complexity increases
Solution Approach 1:
The patent introduces dynamic elements (extension springs) to each conductive blade that can be adjusted via cam surfaces to provide the necessary contact force and overtravel. This dynamic adjustment capability allows the system to compensate for wear and maintain reliable contact engagement, while the modular spring-cam configuration keeps the added complexity manageable and localized to each blade assembly.
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 solution effectively reduces the magnitude and impact of uneven erosion, maintaining consistent contact force and overtravel range, thereby enhancing the reliability and longevity of the circuit breaker.
Implementation Method 1
each conductive blade has associated therewith an extension spring(s), which has one end connected to a pivot pin on the conductive blade and an opposite end connected to a fixed pin on the carrier. The extension spring of each of the conductive blades is used to control the over travel and contact force of the conductive blade.
Implementation Method 2
The two conductive blades of the blade assembly are rotatably mounted in the carrier such that the pivot pin of each conductive blade cams against a corresponding one of the cam surfaces of the carrier to control movement of the conductive blades between the closed position and an initial open position
Implementation Method 3
Each of the two conductive blades has a movable electrical contact configured to engage a corresponding one of the stationary electrical contacts in a closed position and to disengage from the corresponding one of the stationary electrical contacts in an open position.
Data Source
Figure 1
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AI summary
An interrupter module (10) of a molded case circuit breaker (2) includes two stationary electrical contacts (20), and a blade carrier assembly (100) with a blade assembly (130) and a carrier (160) for the blade assembly. The blade assembly includes two conductive blades (140A, 140B). Each blade includes a movable electrical contact (150A, 150B) for engaging a corresponding stationary electrical contact in a closed position and for disengaging from the corresponding stationary electrical contact in an open position. Each blade has an independent over travel and contact force to maintain contact between the movable electrical contacts and corresponding stationary electrical contacts in the closed position.