Insulation is a nonconductive material, or a material resistant to the flow of electric current.It is often called a dielectric in radio frequency cables. Insulation resists electrical leakage, prevents the wire’s current from coming into contact with other conductors and preserves the material integrity of the wire by protecting against environmental threats such as water and heat. The safety and effectiveness of the wire depend on its insulation.

PVC -A PVC jacket is a relatively inexpensive and easy-to-use material with the potential to be used in diverse applications. The maximum temperature range is minus 55 degrees Celsius to 105 degrees Celsius and is resistant to flame, moisture and abrasion. It also holds up against gasoline, ozone, acids and solvents. It can also be used for medical- and food-related purposes as it is odorless, tasteless and nontoxic. PVC jackets can be used in heavy- and thin-wall applications. PVC should not be used when flexibility and an extended flex life are required at low temperatures. When used in retractile cord applications, it also shows below-average flexibility. PVC jackets display high attenuation and capacitance loss, meaning that power is lost when used in an electrical system.

PE -This compound is used most in coaxial and low-capacitance cables because of its exemplary electric qualities. Many times, it is used in these applications because it is affordable and can be foamed to reduce the dielectric constant to 1.50, making it an attractive option for cables requiring high-speed transmission. Polyethylene can also be cross-linked to produce high resistance to cracking, cut-through, soldering, and solvents. Polyethylene can be used in temperatures ranging from negative 65 degrees Celsius to 80 degrees Celsius. All densities of polyethylene are stiff, hard and inflexible. The material is also flammable. Additives can be used to make it flame-retardant, but this will sacrifice the dielectric constant and increase power loss.

PP -This material is very similar to Polyethylene but has a wider temperature range of minus 30 degrees Celsius to 105 degrees Celsius. It is used primarily for thin-wall primary insulations. Polypropylene can be foamed to improve its electrical properties.

TPR -In many applications, TPR is used to replace true thermoset rubber. It has improved colorability, higher processing speeds and a wider usable temperature range. It also displays excellent heat, weather and age resistance without curing. TPR is not cut-through resistant but can be used in applications where other properties of rubber are preferred.

TPU -Thermoplastic polyurethane (TPU) is the go-to overmolding material for watertight applications or products that must survive harsh environments. Thermoplastic polyurethane also features good electrical insulation up to 1,000 V (exceeding the required 108 Ohm-cm by standard ISO6722).

The Difrence Between TPU and PVC

Cables for fixed installation in wire channels or long walls or long sealings of rooms need to be bendable. Cores for moveable electric devices and units need to be flexible. The required processability is achieved by using stranded conductors inside the cable which are produced on stranding machines.

Stranding is the process where a particular number of stranding elements are joined together while winding them round a common axis.

Stranding is a result of rotating and forward movement. The rotation creates winding of the stranding elements around an axis or a center element. The forward movement is made using a capstan.

The most common and simplest stranding system is the 6-wire system. This system has a center element and 6 wires are helically laid around this center element. All additional layers on top of this one have 6 wires more than the layer before. For example 1+6+12+18+24 etc.

When using the 6-wire system all wires in all layers have exactly the same diameter. Such a design is called concentric design.

Lay-length -The lay-length is the measurement parallel along the axis that every individual stranding element needs for one complete winding around the axis.

Stranding direction -The stranding direction can be indicated when looking on the rope in the roll axis. When looking on a right-stranded rope the stranding elements are going from front left to down right. For this direction the character “Z” is indicated. The character “S“ is symbolic for left stranding. The assignment of “S” or “Z” is related to the center of the character which either goes right to left or left to right.

The cross lay stranding has an opposite direction of each layer to the one before.

When designing the cable with mono lay all layers have the same stranding direction.

Single Twist Bunching

The advantage of the single twist bunching machine is a spinning of the take-up reel around its centre axis.

The production speeds to be achieved are in comparison to a drum twister much higher. The single twist buncher is limiting the bending radius of the ingoing individual products. In case the min. achievable bending radius of the single conductor is bigger than the bending radius inside the single twist machine another way of production has to be selected for example drum twister Thanks to modern control technology the single twist machines can perform good stranding results for the entire production length.

Double Twist Bunching

The double twist bunching machine is making two twists in turn of the bow. In the double twist bunching machine the take-up bobbin or reel is installed and a bow is rotating around the pay-off. The pay-offs for the individual products are outside of the machine. The machine usually has a housing. In addition to bobbins barrels can be used as pay-off for the individual wires. The individual elements are outside the machine housing and are going to the lay-plate in front of the machine. From the lay-plate they are going through the bow where the two twists are added before going onto the spool or drum.

Compacting can also been done in Double Twist Bunching Machines.

Compacting

Round conductors -When compacting a round conductor this is usually made using the stranding nipple and/or compacting rollers. Both ways of compacting are reducing the cross section of the individual wires until the strand has the requested diameter. The geometric shape of the cross section regarding the single wire is unevenly changed.

Sector conductors -To reduce the cross section of stranded conductors, especially for energy cable, sector shaped conductors are replacing round conductors. Multi wire sector conductors are always compacted.

Depending on cable design there are 60°, 90°, 100° and 120° sectors. The sum of the angle of the individual conductors has to be 360°.

Compacting and production of sector shaped conductors is usually made using compacting rollers.

Armor is a metal layer wrapped around the exterior of a cable to provide mechanical protection. It is primarily used in hazardous environments that require an extra layer of cable defense, or in situations where Type MC (metal clad) cable is required by the National Electric Code.

The metal armor can protect the cable against falling objects, crushing, and other physical damage. It also adds extra fire resistance, is safer for electrical maintenance workers, and is can be used in both Riser and Plenum applications. Even in markets with strict building regulations, armoring makes almost any electronic cable installation possible.

Common Cable Armor Materials

The most common armor materials are interlocked galvanized steel, interlocked aluminum, and corrugated-and-welded aluminum. All are similarly priced and, in most applications, steel and aluminum armor are equally sufficient. However, there are a few characteristics that set them apart and could make one more appropriate for a specific application.

Steel - This material is crush resistant and impact resistant. It is stronger than aluminum, but it also 10-40% heavier. In high current applications, steel is more effective than aluminum at blocking electromagnetic interference.

Aluminum - Aluminum is about five times more conductive than steel armor and weighs much less. It is impact resistant, but in order to achieve the same crush resistance as steel, aluminum armor must be five mils thicker. In low current applications, aluminum better shields cable from electromagnetic interference.

Armor vs. Shielding

Many times the idea of armor and shielding go hand in hand. Although both are metal layers used in cable to provide protection, each provides a very different kind of protection. Armor, located on the outside of the cable, is a sturdy layer of metal designed to protect mechanical integrity. It defends the cable against physical hazards and prevents it from being crushed or damaged by outside forces. Shielding is incorporated in the inner layers of the cable, around the conductor. It works to minimize electromagnetic interference and prevents the cable from intercepting outside currents or signals that could damage its productivity. Whether armor and shielding are both used in a cable depends on the application for which it is being designed.