Three-Phase Motor Protector Thermal Plate Fixing
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Solution Overview
Problem
The conventional protector for three-phase electric motors with a thermally responsive plate experiences strain concentration and deformation issues due to the formation of a through-hole, leading to cracks and compromised AC current interruption precision.
Innovation Solution
A protector design that eliminates the through-hole by using an elastic member and a rotation preventing member to maintain the original reversing characteristic of the thermally responsive plate, ensuring precise AC current interruption without deformation limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a through-hole is formed in the central part of the thermally responsive plate for fixing to the support, then the thermally responsive plate can be fixed to the support by swaging or screwing, but strain concentration around the through-hole causes cracks and limits the movement of the plate during reversal and return
Solution Approach 1:
The invention extracts the through-hole from the thermally responsive plate structure. Instead of forming a through-hole in the plate, the support is designed with a projection that fits into a recess on the plate's surface, providing fixing stability without compromising the plate's structural integrity and crack resistance.
2Adaptability or versatility
If the thermally responsive plate is formed into a dish shape by drawing, then the plate can reverse direction at predetermined temperature, but the central part undergoes largest deformation and movement is limited when fixed with a through-hole
Solution Approach 1:
The through-hole is removed from the plate structure. The fixing mechanism is transferred to the support component, which has a projection that engages with a recess on the plate. This allows the dish-shaped plate to undergo full deformation during thermal reversal without being constrained by a central through-hole.
3Stability of the object's composition
If the thermally responsive plate is fixed to the support by swaging or screwing through a through-hole, then the plate can be securely attached, but the original reversing characteristic cannot be maintained and AC current interruption precision is compromised
Solution Approach 1:
The through-hole is extracted from the plate design. The support structure incorporates a projection that fits into a recess on the plate surface, providing secure attachment without interfering with the plate's thermal reversal characteristics and temperature response precision.
Solution Approach 2:
The recess and projection mechanism acts as an intermediary fixing solution between the plate and support. This intermediate structure provides stable attachment while allowing the plate to maintain its original reversing characteristic and respond precisely to temperature changes.
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 allows the thermally responsive plate to maintain its original reversing characteristic, ensuring precise interruption of AC current flowing into the three-phase motor, while preventing crack formation and enhancing the protector's reliability.
Implementation Method 1
a thermally responsive plate (32) formed into a dish shape by drawing so as to reverse a direction of curvature at a predetermined temperature
Implementation Method 2
an elastic member (34) holding a central part of the thermally responsive plate (32) between the protrusion (35) and the elastic member (34), thereby biasing the thermally responsive plate (32) in such a direction that the thermally responsive plate (32) departs from the fixed contacts (27)
Data Source
AI summary
A protector for a three-phase electric motor has a container with a housing and a metal plate secured thereto. A protrusion is provided in the housing. Three conductive terminal pins, each with a fixed contact, protrude into the housing through the metal plate. A thermally responsive plate is connected to the three moveable contacts. The thermally responsive plate is dish shaped and reverses its direction of curvature at a predetermined temperature. Three moveable contacts are secured to the thermally responsive plate. An elastic member extends between the protrusion and the thermally responsive plate. A rotation member prevents the thermally responsive plate from rotating, thereby maintaining the moveable contacts in opposition to the fixed contacts. The conductive terminal pins are located at a neutral point side of phase windings of a three-phase motor so that AC current flowing into the three-phase motor is interrupted.