ASD Cable Termination with Tinned-Copper Braids for Stray Current Management
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Solution Overview
Problem
Traditional cable systems fail to provide a low-impedance path for high-frequency stray currents generated by Adjustable Speed Drives (ASDs), which can damage the drives and nearby equipment, and internal vibrations affect long-term connection viability.
Innovation Solution
A cable and termination system with three insulated phase conductors and three ground conductors, where the ground conductors collectively have a total cross-section of at least half that of a phase conductor, and a copper tape shield with a galvanized steel armor, along with a termination system using tinned-copper braids and connectors to ensure a low-impedance path for stray currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional grounding conductor is used in ordinary cable, then the cable structure is simple, but it cannot provide a low impedance path for stray currents at high frequencies
Solution Approach 1:
The grounding function is segmented into multiple components: individual ground conductors for each phase, copper tape shielding layers, and interwoven ground wires. This segmentation allows each component to address specific frequency ranges and current paths, achieving low impedance across broad spectrum while maintaining manageable structural complexity through modular design
Solution Approach 2:
The cable employs composite grounding structure combining copper tape (for high-frequency shielding), stranded ground wires (for flexibility and low-frequency conduction), and geometrically arranged ground conductors. This composite approach leverages the complementary properties of different materials to achieve broad-spectrum low impedance performance
2Reliability
If multiple geometrically placed grounding conductors are added for low frequency noise, then stray current conduction improves, but cable complexity increases
Solution Approach 1:
The ground conductors are designed to serve multiple functions simultaneously: providing low-frequency noise conduction, maintaining cable geometric symmetry for balanced phase conduction, and working in conjunction with copper tape shielding for high-frequency protection. This multi-functionality reduces the need for separate dedicated components for each function
Solution Approach 2:
Multiple ground conductors are geometrically arranged to maintain equipotential relationships across all phases, ensuring balanced current distribution and minimizing differential mode noise. The symmetric placement creates equivalent electrical paths for each phase, reducing common mode currents
3Reliability
If cable insulation is designed to withstand high transient voltage stress, then insulation reliability improves, but manufacturing complexity increases
Solution Approach 1:
The insulation material parameters are specifically selected and adjusted to withstand transient voltage stresses of 2-3 per-unit levels. This involves choosing materials with appropriate dielectric strength, breakdown voltage, and impulse resistance characteristics, allowing the insulation to handle ASD-generated transient overvoltages while maintaining standard manufacturing processes
4Reliability
If copper tape shield is applied helically with overlap, then shielding effectiveness improves, but cable diameter and flexibility are reduced
Solution Approach 1:
The copper tape is applied in a helical pattern around the cable core, creating a continuous overlapping shield that follows the cable's curvature. This helical application maintains shielding effectiveness by ensuring overlapping coverage while accommodating cable bending and flexibility requirements better than rigid spiral or flat configurations
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 system effectively manages high-frequency noise and provides long-term reliability by ensuring a low-impedance path for stray currents and secure connections, reducing attenuation and maintaining performance under vibration.
Implementation Method 1
the ground conductors collectively having a total cross-section of at least one-half of the cross-section of a phase conductor... Wrapped around the cable core is a cable wrap, including copper tape, applied helically over the cable core
Implementation Method 2
The termination which forms an integral part of the present invention includes a plurality of connectors and tinned-copper braids, where the braids are secured about the copper tape of the cable core... providing a low-impedance ground path for common mode (stray) currents
Implementation Method 3
a cable and termination system... with three ground conductors... Wrapped around the cable core is a cable wrap, including copper tape, applied helically over the cable core or any binding tape, with an overlap of fifty percent, and an overall jacket
Data Source
AI summary
A cable and termination system for use with adjustable speed drives, including flexible tray cables and metal-clad cables, and terminations coupled therewith. The cables generally include three phase conductors, three ground conductors and fillers, and are wrapped with copper tape and other elements. The terminations coupled with the cables include a plurality of connectors and flexible, tinned-copper braids which act as the shield termination for the copper tape. More detailed and other embodiments of the present invention are disclosed in the specification hereof.