The term “tray cable” was developed through its installation in cable tray. Each type of insulation is engineered to be able to withstand some type of environmental condition that could possibly damage the copper underneath it. In cable tray, insulation would come in contact with moisture, oils and solvents and if it’s not protective enough to withstand those things the copper could be affected.
The first two things to determine about your tray cable will be the voltage and the shielding. There is a 300 volt version called PLTC (Power Limited Tray Cable) and a 600 volt “tray cable” for applications requiring more power. There are three versions of shielding that are offered including unshielded, shielded and individually shielded.
Tray Cable Shielding
An unshielded tray cable is the cheapest and most basic version you can get if your application doesn’t need to block EMI (Electromechanical Interference). When two cables run next to each other in tray or duct there can be a certain amount of interference which is blocked with a shield over the conductors. An aluminum foil polyester shield wraps around all of the conductors to limit the amount of EMI. To picture it in your mind, imagine a glowing circumference pulsating around each of the cables. When they connect there’s “interference” so the shielding shrinks that circumference to limit the amount of interference.
An individually shielded tray cable has a shield around each pair of wires inside the cable. So a “3 pair” cable has an individual shield around each pair and an overall shield wrapping around all of the conductors together. This is needed when each pair can interfere with each other. The shield will limit the EMI between each set of two wires so that there is a clean signal passing through.
Flexible Tray Cables
Once you decide the voltage and the shielding for your tray cable you will just need to figure out the AWG (American Wire Gauge) and the amount of copper conductors. The flexibility remains the same throughout most tray cables because the installation types are nearly all the same. When a cable is being snaked through duct, or pushed through cable tray, added flexibility would only hurt the process. Therefore, most tray cables come with stiff copper strands to keep a firm hold during the installation in tray and duct.
There are plenty of flexible electronic cables available that are similar to tray cables that can be used if your installation is a bit different than the standard. So, make sure that the insulation with withstand everything that the cable will be exposed to and include the option of added flexibility to your cable. It will bend easier and wrap around corners easier but it will not be the best option for a cable installed in conduit or duct.
Written by: Chris Bell