Wire
Cable tray wire, or tray cable, is rated and approved for installation in raceways and cable trays. The cable is made of individual conductors covered with armor for insulation and a jacket that can withstand abrasion. Because tray cables pass strict crush and impact tests, they do not require conduit and can leave cable tray or raceways up to six feet, as long as they are secured and supported. Tray cables can be rated for indoor and outdoor use, and hazardous and corrosive areas.
MTW wire (Machine Tool Wire) consists of stranded, bare copper conductors insulated with polyvinyl chloride (PVC). The stranding gives the wire more flexibility for routing in tight spaces such as electrical cabinets. MTW wire has corrosion protection and is resistant to moisture, heat, oil and gasoline. It is rated up to 600 V and 105 degrees Celsius.
THHN wire (Thermoplastic High Heat-resistant Nylon) consists of a stranded or solid, bare copper or aluminum conductor with a thermoplastic insulation and a nylon jacket. THHN is a building wire usually used to carry electricity to external power sources. It is rated up to 600 V and 90 degrees Celsius in dry locations, 75 degrees Celsius in wet locations.
Industrial Wire Types: Part 1
THHN
Thermoplastic, High Heat resistant, Nylon jacket insulation (THHN) wire is used in conduit or in cable trays due to its rigidity and tough insulation characteristics. THHN can be stranded (several small strands of wire grouped together), allowing for more flexibility and less chance of breakage, or solid (one wire), which is more durable and rigid. THHN wire is suitable for use in dry locations with temperatures that do not exceed 90 degrees Celsius.
XHHW
Cross-linked polyethylene, High Heat-resistant, Water-resistant (XHHW) wire is very similar to THHN. The difference is that XHHW wire is overall a more durable wire that can withstand higher temperatures and is water resistant. XHHW wire can also be found in both stranded and solid wire options.
MTW
Machine Tool Wire (MTW) wire is much more flexible than THHN wire with insulation that is not as durable, making it a poor choice to run through conduit. The flexibility makes it ideal for winding through tight areas, such as wire ducting in an industrial control cabinet. MTW wire is almost exclusively found in stranded wire, which allows for much of the flexibility and reduces the chances of the wire breaking. MTW wire is intended for use in dry locations that do not exceed 90 degrees Celsius or wet locations that do not to exceed 60 degrees Celsius.