Current Transformer Cabinets and Terminal Enclosures
Current transformer (CT) cabinets house current transformers that are used to convert a primary current into a secondary current, usually reducing a large current into a smaller current for measurement and protection. Due to the large currents involved, it is important that CT cabinets provide the necessary protection and prevent possible electric shock. CT cabinets must meet the safety standards of Underwriters Laboratories (UL) and National Electrical Manufacturers Association (NEMA). The standards set for CT cabinets is UL Type 1 and NEMA Type 3R. Most CT cabinets are made of aluminum, galvanized steel or stainless steel.
Terminal enclosures are similar to junction boxes in that they house one or more wiring connections. Terminal enclosures are designed to protect the connections from environmental conditions and accidental contact. They are typically available with 3 or 4 wire configurations in sizes up to 440 A. They are constructed to meet UL Type 1, NEMA Type 3R and UL 1773 standards. UL 1773 is specific to terminal enclosures. Most terminal enclosures are made of aluminum or steel.
Products
Enclosure Selection Basics
Electrical enclosures are cabinets that are designed to house electrical components. Their main function is to protect the components, as well as to protect the operators from electrical hazards. Enclosures are typically made of solid plastics, fiberglass and metal materials, such as carbon steel, stainless steel and aluminum.
One of the most important things to consider when selecting an electrical enclosure is the NEMA rating. NEMA stands for National Electrical Manufacturer Association. They have developed a rating system which determines the types of environments an electrical enclosure can be used in.
NEMA 1 and a NEMA 12 enclosures
Both of these enclosures are intended for indoor use only. They are both dust resistant. The NEMA 12 enclosure is rated for damp environments. The NEMA 1 is rated only for dry environments.
NEMA 4 and NEMA 4X enclosures
Both of these enclosures can be used indoors as well as outdoors. They are both dust resistant. They are also water resistant and corrosion resistant. NEMA 4X has an extra layer of corrosion resistance.
NEMA 7 enclosures
This is a more specific type of enclosure that is rated for use in hazardous environments. It is rated to contain an explosion within the enclosure and not cause any sort of external hazard.
Size
When selecting the size of an enclosure, it is important to consider the following: how much space will the electrical components occupy, how much space is needed around each component, is there enough room to run all of the wires and how much space is needed outside of the enclosure?
Temperature
When selecting an enclosure, it is important to consider both the ambient temperature and the temperature that is generated inside of the enclosure. When an enclosure is located outside in direct sunlight, that heat can be transferred inside the enclosure. Also, each component inside of the enclosure generates a certain amount of heat.