1.3 Insulation & Cable Structures: Environmental Armor

Sector Conductor: A sector conductor is a stranded conductor whose cross-section is approximately the shape of a sector of a circle. A multiple conductor insulated cable with sector conductors has a smaller diameter than the corresponding cable with round conductors.

Compact Strand: A compact stranded conductor is a round or sector conductor having all layers stranded in the same direction and rolled to a predetermined ideal shape. The finished conductor is smooth on the surface and contains practically no interstices or air spaces. This results in a smaller diameter.

Compressed Strand: Compressed conductors are intermediate in size between standard concentric conductors and compact conductors. A comparison is shown below:

1.3.3.1.1 Wire Cable Types

Single-Core Cable

Arequire single-core cable consists of a single conductor surrounded by a layer of insulation and, in some cases, an outer jacket. The conductor is the current-carrying element, usually made of copper or aluminum. The insulation prevents direct contact with other conductors or the environment, ensuring electrical safety and signal integrity.

• Construction: One central conductor.
• Application: Commonly used in power distribution, both AC and DC systems, where separate conductors for different phases, neutral, or earth are run independently. For example, wiring for residential power circuits or high-voltage transmission lines.

Multi-Core Cable

A multi-core cable contains two or more insulated conductors bundled together within a single outer jacket. These individual conductors are called 'cores'. This configuration simplifies installation by consolidating multiple wires into one manageable assembly.

• Construction: Multiple insulated conductors laid up (often twisted or parallel) and enclosed in a common protective sheath.
• Application: Ubiquitous in control systems, instrumentation, data communication, and multi-phase power applications where multiple connections are needed between two points (e.g., control panels, network wiring, and appliance power cords).

Shielded Cable

A shielded cable is an electrical cable that includes a conductive layer, or shield, to protect the inner conductors from electromagnetic interference (EMI). EMI, also known as radio-frequency interference (RFI), can degrade signal quality and disrupt data transmission. The shield is typically grounded and works by reflecting or absorbing the interfering noise.

• Construction: The shield can be a braided mesh of copper wires, a solid or laminated conductive foil (like aluminum foil), or a combination of both. It is positioned around the insulated conductor(s) but beneath the outer jacket.
• Application: Essential for data cables (like Ethernet), audio/video cables (like coaxial cables), and instrumentation wiring in environments with high electrical noise, such as industrial plants or near motors and transformers.

Flat Cable

A flat cable consists of multiple conductors running parallel to each other in the same flat plane. As a result, the cable has a wide and flat profile. The conductors are individually insulated.

• Construction: Parallel conductors laminated between flexible insulating materials.
• Application: Frequently used in applications requiring high flexibility and space efficiency, such as in robotics, automated equipment, and elevators, where repeated bending and movement occur.

Ribbon Cable

A ribbon cable, also known as a multi-wire planar cable, is a specific type of flat cable where the conductors are arranged in a precise, parallel, and evenly spaced manner, resembling a ribbon. This design allows for mass termination with insulation-displacement connectors (IDCs).

• Construction: Multiple small-gauge wires running parallel, bonded together by a flexible insulating material.
• Application: Widely used for internal interconnections within electronic equipment, such as connecting peripherals to a motherboard inside a computer, due to its space-saving design and ease of termination.

Coaxial Cable

A coaxial cable is designed to transmit high-frequency signals with low loss. It features a central conductor surrounded by an insulating dielectric, which is then enclosed by a metallic shield (braid or foil) and an outer insulating jacket. This concentric construction creates a controlled electromagnetic field, minimizing signal radiation and susceptibility to EMI.

• Application: Used for cable television (CATV), broadband internet, and radio frequency (RF) applications.

Copper Calculations in Cables

Copper is an essential part of wires and cables and is listed on the stock exchange. 

The name DEL is derived from the German exchange "Deutsche Elektrolytkupfer Notiz für Leitzwecke". Based on the official quotation at the LME (London Metal Exchange), the value of the DEL list is calculated every trading day. The standard price for automotive cables is based on a copper value of 150.00 EUR / 100 kg.

Copper Weight [g / km] x ( ( Medium DEL [EUR / 100 kg] + 1 % procurement costs ) - copper base [EUR / 100 kg] ) / 100 = Copper Surcharge [EUR / km]

Example Calculation of Copper Surcharge

The total price will be the quoted price in the online shop + copper surcharge (in EUR / km):

9.60 [kg / km] x ( ( 590.00 [EUR / 100 kg] + 5.90 [EUR / 100 kg] ) - 150.00 [EUR / 100 kg] ) / 100

= 42.81 [EUR / km]

19.2.2.1.2 Wire Insulations

Wire insulation is the non-conductive material surrounding a wire's conductor. Its primary job is to prevent short circuits by keeping the conductor from touching other conductors or conductive surfaces. It also protects the wire from environmental factors like moisture, chemicals, and physical damage.

The selection of the right insulation is a critical engineering decision that directly impacts the safety, reliability, and lifespan of a cable harness.

1.3.3.2 Selection Criteria ⚙️

Choosing the correct insulation involves balancing performance requirements and cost. The main criteria are:

• Electrical Requirements: The insulation must have a high enough dielectric strength to withstand the system's voltage without breaking down.
• Temperature Range: It must perform reliably within the expected operating temperature range, from the coldest startup condition to the hottest peak temperature, without becoming brittle or melting.
• Mechanical Stress: The material must be tough enough to handle the physical demands of the application, including resistance to abrasion, cutting, vibration, and flexing.
• Chemical and Fluid Resistance: It must not degrade when exposed to fluids it might encounter, such as oil, fuel, hydraulic fluid, or solvents.
• Environmental and Safety Requirements: The application may have specific safety rules, such as requiring materials that are halogen-free or UV resistant.

19.2.2.1.4 Common Insulation Materials & Chemical Structure

Different chemical structures give insulation materials their unique properties.

• PVC (Polyvinyl Chloride): A vinyl polymer thermoplastic. It's the most common and cost-effective insulation. It has good general-purpose resistance to moisture and abrasion but has a limited temperature range and contains halogens.
• XLPE (Cross-linked Polyethylene): A polyolefin thermoset. The "cross-linking" process creates strong chemical bonds between polymer chains, giving it superior thermal stability, toughness, and chemical resistance compared to standard polyethylene or PVC. It's widely used in automotive and industrial applications.
• Silicone: An inorganic polymer. Its silicon-oxygen backbone makes it extremely flexible and gives it an excellent, wide temperature range (e.g., -60°C to 200°C). However, its mechanical strength is poor, meaning it has low resistance to cutting and abrasion.
• PTFE (Teflon) & other Fluoropolymers (FEP, ETFE): These are fluorocarbon-based polymers. The strong carbon-fluorine bonds give them exceptional resistance to high temperatures and chemicals. They also have a very low coefficient of friction, making them easy to pull through conduits. They are considered high-performance materials and are used in demanding aerospace and industrial applications.

19.2.2.1.5 Special Applications and Formulations

• Halogen-Free (LSZH - Low Smoke Zero Halogen): Standard insulators like PVC contain halogens (chlorine). When they burn, they release thick, toxic, and corrosive smoke. Halogen-free materials are used in enclosed or poorly ventilated spaces like aircraft, ships, subways, and data centers. In a fire, they produce very little smoke and no toxic halogenated gases, improving safety and evacuation.
• Sulfur-Free: This is a highly specific requirement for high-temperature applications that use silver-plated copper wire. At high temperatures, any sulfur present in the insulation material can react with the silver plating, forming silver sulfide (tarnish). This corrosion degrades the conductor, increases resistance, and can lead to connection failure. Therefore, the insulation used with silver-plated wire must be certified as sulfur-free.
• UV Resistance: For cables used outdoors, the insulation must contain additives to resist degradation from ultraviolet (UV) radiation from the sun. Without this protection, the material would become brittle and crack over time.

19.2.2.2 Connectors

Connectors are critical electromechanical devices in cable harnesses, providing a separable interface for electrical circuits. They allow harnesses to be easily connected to and disconnected from equipment, enabling modular design, simplified manufacturing, and efficient maintenance.

Connectors in cable harnesses are terminated using several methods, but the two most prevalent are crimp terminals and insulation-displacement connectors (IDC). Each method offers distinct advantages in reliability, production speed, and application suitability.

19.2.2.2.1 Connector Anatomy

A typical industrial connector isn't just a simple plug; it's an assembly of precision components designed to maintain a reliable connection in demanding environments.

• Housing: The outer shell that encases the internal components. It provides mechanical protection, alignment during mating, and electrical insulation. Housings are typically made from engineered polymers (like PBT or Nylon) for insulation and light weight, or metals (like aluminum or stainless steel) for durability and EMI shielding.
• Terminals / Contacts: These are the conductive elements within the housing that make the actual electrical connection. They are precision-machined from highly conductive copper alloys and are often plated with materials like golddie-blades or tin.rotary Gold plating provides excellent corrosion resistance and low contact resistance, crucial for low-level signals, while tin is a cost-effective choice for power applications.
• Seals & Gaskets:strippers In industrial settings, connectors must often protect against moisture, dust, and chemicals. Elastomeric seals (made from silicone, neoprene, or Viton) are integrated into the connector's design to achieve a specific level of environmental protection. This is quantified by an Ingress Protection (IP) rating, such as IP67, which signifies the connector is dust-tight and can be submerged in water.
• Locking Mechanism: To prevent accidentalconductor disconnectiondamage due to vibrationthe orforce pulling,required industrialto connectorscut featurethe robusttough lockinginsulation.
  mechanisms.

  1.3.2 CommonComplex typesCable include:

1. Threaded Coupling: A screw-on mechanism providing a very secure, vibration-resistant connection.
2. Bayonet Lock: A quick, push-and-twist mechanism common in militaryStructure and RFRisks connectors.
3. Push-Pull

   Beyond Latch:single Allowswires, forcomplex quickcables connectionintroduce and disconnection but provides a strong lockgeometry that cancontrols onlyelectrical beperformance. releasedAltering bythis pullinggeometry during processing destroys the cable's function.

   A) Coaxial Cables (RF Signals)

   Coaxial cable performance relies on the connector's outer sleeve.

Connectors in cable harnesses are terminated using several methods, but the two most prevalent are crimp terminals and insulation-displacement connectors (IDC). Each method offers distinct advantages in reliability, production speed, and application suitability.

Crimp Connectors

A crimp connector is a type of solderless electrical connection. It uses a specialized tool to mechanically deform a metal terminal around a wire's conductor, creating a secure, gas-tight joint. This method is widely used because it's fast, reliable, and creates a strong mechanical and electrical bond.

This process has two key parts:

1. Conductor Crimp: The main barrel of the terminal is squeezed tightly around the metal strands of the wire. The intense pressure forms the wires and the terminal into a single, solid mass, creating a cold weld. This forms a reliable, low-resistance electrical connection that prevents oxygen and moisture from getting in and causing corrosion.
2. Insulation Crimp: A second part of the terminal is lightly crimped around the wire's insulation. This doesn't make an electrical connection; instead, it acts as strain relief, protecting the delicate conductor strands from breaking due to vibration or movement.

Key Components;

• Wire: The conductor that needs to be terminated. The end must be stripped of its insulation to a precise length.
• Crimpconcentric Terminal: A specially designed metal piece (often tin-plated copper) that receives the wire.
• Crimping Tool: A specialized tool with dies shaped to match the terminal. Using the correct tool is critical for a proper crimp; using pliers or the wrong tool will result in a failed connection.

Insulation-Displacement Connectors (IDC)

IDC is a connection method where the terminal has sharp, precisely engineered tines or blades that pierce directly through the wire's insulation to make contact with the conductor. This eliminates the need for wire stripping, dramatically speeding up the assembly process.

• Process:

1. An insulated wire is placed into a slot on the connector.
2. A specialized tool or press pushes the wire into the slot, causing the sharp tines to displace the insulation and make a secure electrical connection with the conductor.

• Characteristics:

1. Speed & Automation: The elimination of wire stripping makes IDC ideal for high-speed, automated mass termination, especially for multi-conductor ribbon cables.
2. Specific Design: IDC connectors are designed for specific wire gauges and insulation types (typically solid or stranded PVC-insulated wires).
3. Common Applications: Widely used inside computers (e.g., floppy and PATA hard drive cables), networking, and telecommunications equipment where high-density, low-cost connections are required.

19.2.2.2 Terminals

Terminals are the metal components at the ends of wires that create a secure and reliable point for an electrical connection. They are the crucial interfacespacing between the wire'scenter conductor and the restshield, ofmaintained by the electrical system, whether it's another wire, a screw post, or the pin in a connector.

19.2.2.2.1 Crimping Terminalsdielectric

These are the most common type of terminal found inside multi-pin connectors. They are precision-stamped components designed to be crimped onto a wire and then inserted into a connector housing..

• Structure: TheyCenter Conductor – Dielectric – Shield (Braid/Foil) – Jacket.
• Processing Risk (Crushing): Using a clamp or tie-wrap that is too tight crushes the soft dielectric (e.g., foam PE). This changes the capacitance and impedance at that spot, causing signal reflection (VSWR failure).
• Stripping Risk: Cutting too deep slices the shield strands; cutting too shallow leaves dielectric residue on the center pin. Rotary stripping machines are mandatory for repeatability.

B) Twisted Pair (Differential Signals)

Twisted pairs (e.g., CAN bus, Ethernet) reject electromagnetic interference (EMI) via their specific twist rate (lay length).

• Untwisting Limit: When terminating, the "untwist" length must be minimized (typically have≤ 13 mm or 0.5 inch) to maintain noise rejection. Excessive untwisting creates an "openantenna" barrel"for noise right at the connector.

C) Shielded Cables (EMI Protection)

Shields (foil or "F-crimp"braid) designcontain withinternal twonoise setsand ofblock wings.external Onenoise.

• Termination: isThe crimpedshield aroundmust be terminated 360 degrees (via backshell) or via a drain wire. Pigtailing (twisting the barebraid wire conductor to createinto a gas-tightwire) electricalintroduces bond,high whileinductance theand secondshould setbe iskept crimpedas aroundshort theas wire's insulation to provide mechanical strain relief.possible.
• Usage:Stripping Risk: UsedSlicing insidethe multi-pinshield plasticduring connectorsjacket inremoval nearlybreaks allthe industries,ground includingpath. automotive,Using aerospace,a andscribe-and-break consumertechnique electronics,or tothermal createstripping serviceableavoids andthis robust connections.damage.

1.3.3

Ribbon

19.2.2.2.2and QuickFlat DisconnectsFlex Cables (Blade or Spade Terminals)FFC)

Flat cables offer high density and repeated flexing but are mechanically fragile.

A) Pitch Definitions

Pitch is the center-to-center distance between conductors.

• Ribbon Cable:These Standard pitch is 1.27 mm (0.050 inch) designed for IDC (Insulation Displacement Connectors).
• FFC (Flat Flexible Cable): Common pitches are 0.5 mm and 1.0 mm.

B) Processing Risks