Coaxial Cable Shield Folding to Prevent Partial Discharge
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Solution Overview
Problem
The occurrence of partial discharge due to gaps between the folded portion of the shield wire and the insulator in coaxial cables used in time-of-flight mass spectrometers leads to voltage noise, affecting measurement accuracy by disturbing the electric field and causing local electric field concentration, which in turn affects the time-of-flight of ions.
Innovation Solution
A method involving a folding processing step to form a folded portion of the shield wire and a burying processing step to dispose an insulating or semi-conductive buried member in the gap between the folded portion and the insulator, followed by a cover processing step to secure the buried member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shield wire is folded back toward the outer sheath side to secure creepage distance, then electrical safety is improved, but a gap is generated between the folded portion and the insulator causing partial discharge
Solution Approach 1:
A filler material is introduced as an intermediary substance to occupy the gap between the folded shield wire and the insulator. This mediator eliminates the harmful air-filled gap that causes partial discharge while maintaining the necessary creepage distance for electrical safety.
Solution Approach 2:
The gap-filling treatment is applied locally only at the folded portion where the gap exists, rather than modifying the entire cable structure. This targeted approach eliminates partial discharge at the critical location while preserving the overall cable design and creepage distance requirements.
2Ease of operation
If a gap exists between the folded portion and the insulator, then the shield wire can be folded back for grounding, but electric field concentration occurs causing noise
Solution Approach 1:
The filler material acts as an intermediary that eliminates the gap responsible for electric field concentration, thereby removing the source of noise while preserving the grounding connection capability through the folded shield wire.
Solution Approach 2:
The dielectric properties of the gap region are changed by introducing filler material with appropriate dielectric characteristics. This parameter change eliminates electric field concentration and associated noise while maintaining the electrical functionality of the grounding connection.
3Reliability
If the shield wire is peeled off by a long length to ensure creepage distance, then electrical insulation is improved, but the folded portion becomes larger increasing the gap volume
Solution Approach 1:
The filler material is introduced to occupy the gap created by the extended folding, allowing the shield wire to maintain the necessary creepage distance for electrical insulation while eliminating the harmful gap volume through the intermediary substance.
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
Reduces the occurrence of partial discharge, minimizing noise and maintaining measurement accuracy by stabilizing the electric field, thereby improving the reliability of ion flight time measurements.
Implementation Method 1
when a voltage is applied to the coaxial cable in a state where a gap is generated between the folded portion of the shield wire and the insulator, the electric field is disturbed in the gap, and local electric field concentration occurs, thereby causing partial discharge
Data Source
AI summary
A method for processing a coaxial cable (60) for applying a voltage to a time-of-flight mass spectrometer (10) includes a folding processing step S2 and a burying processing step S3. In the folding processing step S2, a folded portion (66a) is formed by folding a tip end portion of a shield wire (66) to the outer sheath (68) side with respect to the coaxial cable (60) including a central conductor (62), an insulator (64) provided around the central conductor (62), the shield wire (66) provided around the insulator (64), and the outer sheath (68) provided around the shield wire (66). In the burying processing step S3, a buried member (74) having insulating property or semiconductivity is disposed in a gap (72) formed between the folded portion (66a) and the insulator (64).