Electrical enclosure

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Electro polished enclosure (control station), explosion-proof Schaltschrank Enclosure.jpg
Electro polished enclosure (control station), explosion-proof
A municipal electrical enclosure Electricalenclosure.JPG
A municipal electrical enclosure
Allen Bradley programmable logic controller (PLC) installed in an electrical enclosure BMA Automation Allen Bradley PLC 4.JPG
Allen Bradley programmable logic controller (PLC) installed in an electrical enclosure

An electrical enclosure is a cabinet for electrical or electronic equipment to mount switches, knobs and displays and to prevent electrical shock to equipment users and protect the contents from the environment. The enclosure is the only part of the equipment which is seen by users. It may be designed not only for its utilitarian requirements, but also to be pleasing to the eye. Regulations may dictate the features and performance of enclosures for electrical equipment in hazardous areas, such as petrochemical plants or coal mines. Electronic packaging may place many demands on an enclosure for heat dissipation, radio frequency interference and electrostatic discharge protection, as well as functional, esthetic and commercial constraints.

Contents

Standards

Internationally, IEC 60529 classifies the IP Codes (ingress protection rating) of enclosures.

In the United States, the National Electrical Manufacturers Association (NEMA) publishes NEMA enclosure type standards for the performance of various classes of electrical enclosures. The NEMA standards cover corrosion resistance, ability to protect from rain and submersion, etc.

Materials

Electrical enclosures are usually made from rigid plastics, or metals such as steel, stainless steel, or aluminum. Steel cabinets may be painted or galvanized. Mass-produced equipment will generally have a customized enclosure, but standardized enclosures are made for custom-built or small production runs of equipment. For plastic enclosures ABS is used for indoor applications not in harsh environments. Polycarbonate, glass-reinforced, and fiberglass boxes are used where stronger cabinets are required, and may additionally have a gasket to exclude dust and moisture.

Metal cabinets may meet the conductivity requirements for electrical safety bonding and shielding of enclosed equipment from electromagnetic interference. Non-metallic enclosures may require additional installation steps to ensure metallic conduit systems are properly bonded.

Stainless steel and carbon steel

Carbon steel and stainless steel are both used for enclosure construction due to their high durability and corrosion resistance. These materials are also moisture resistant and chemical resistant. They are the strongest of the construction options. Carbon steel can be hot or cold rolled. Hot rolled carbon steel is used for stamping and moderate forming applications. Cold rolled sheet is produced from low carbon steel and then cold reduced to a certain thickness and can meet ASTM A366 and ASTM A611 requirements. [1]

Stainless steel enclosures are suited for medical, pharma, and food industry applications since they are bacterial and fungal resistant due to their non-porous quality. [2] Stainless steel enclosures may be specified to permit wash-down cleaning in, for example, food manufacturing areas.

Aluminum

Aluminum is chosen because of its light weight, relative strength, low cost, and corrosion resistance. It performs well in harsh environments and it is sturdy, capable of withstanding high impact with a high malleable strength. Aluminum also acts as a shield against electromagnetic interference.

Polycarbonate

Polycarbonate used for electrical enclosures is strong but light, non-conductive and non-magnetic. It is also resistant to corrosion and some acidic environments; however, it is sensitive to abrasive cleaners. Polycarbonate is the easiest material to modify.

Fiberglass

Fiberglass enclosures resist chemicals in corrosive applications. The material can be used over all indoor and outdoor temperature ranges. Fiberglass can be installed in environments that are constantly wet.

Terminology

Enclosures for some purposes have partially punched openings (knockouts) which can be removed to accommodate cables, connectors, or conduits. Where they are small and primarily intended to conceal electrical junctions from sight, or protect them from tampering, they are also known as junction boxes, street cabinets or technically as serving area interface.

Telecommunications

Telecommunication enclosures are fully assembled or modular field-assembled transportable structures capable of housing an electronic communications system. These enclosures provide a controlled internal environment for the communications equipment and occasional craftspeople. The enclosures are designed with locks, security, and alarms to discourage access by unauthorized persons. Enclosures can be provided with a decorative facade to comply with local building requirements.

Fire risk

Fire of an electrical cabinet (left : picture, right : simulation with Fire Dynamics Simulator ) Electrical enclosure fire.png
Fire of an electrical cabinet (left : picture, right : simulation with Fire Dynamics Simulator )

Electrical enclosures are prone to fires that can be very intense (in the order of the megawatt) and are hence an important topic of fire safety engineering. [5]

See also

Related Research Articles

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Stainless steel, also known as inox, corrosion-resistant steel (CRES), or Rustless steel, is an alloy of iron that is resistant to rusting and corrosion. It contains at least 10.5% chromium and usually nickel, and may also contain other elements, such as carbon, to obtain the desired properties. Stainless steel's resistance to corrosion results from the chromium, which forms a passive film that can protect the material and self-heal in the presence of oxygen.

<span class="mw-page-title-main">Outside plant</span>

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In physical chemistry and engineering, passivation is coating a material so that it becomes "passive", that is, less readily affected or corroded by the environment. Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material, or allowed to build by spontaneous oxidation in the air. As a technique, passivation is the use of a light coat of a protective material, such as metal oxide, to create a shield against corrosion. Passivation of silicon is used during fabrication of microelectronic devices. Undesired passivation of electrodes, called "fouling", increases the circuit resistance so it interferes with some electrochemical applications such as electrocoagulation for wastewater treatment, amperometric chemical sensing, and electrochemical synthesis.

Surgical stainless steel is a grade of stainless steel used in biomedical applications. The most common "surgical steels" are austenitic SAE 316 stainless and martensitic SAE 440, SAE 420, and 17-4 stainless steels. There is no formal definition on what constitutes a "surgical stainless steel", so product manufacturers and distributors often apply the term to refer to any grade of corrosion resistant steel.

<span class="mw-page-title-main">Monel</span> Solid-solution binary alloy of nickel and copper

Monel is a group of alloys of nickel and copper, with small amounts of iron, manganese, carbon, and silicon. Monel is not a cupronickel alloy because it has less than 60% copper.

<span class="mw-page-title-main">Electrical wiring</span> Electrical installation of cabling

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<span class="mw-page-title-main">IP code</span> Standard for protection against intrusion of dust and water

The IP code or ingress protection code indicates how well a device is protected against water and dust. It is defined by the International Electrotechnical Commission (IEC) under the international standard IEC 60529 which classifies and provides a guideline to the degree of protection provided by mechanical casings and electrical enclosures against intrusion, dust, accidental contact, and water. It is published in the European Union by the European Committee for Electrotechnical Standardization (CENELEC) as EN 60529.

<span class="mw-page-title-main">Electrical equipment in hazardous areas</span> Electrical equipment in places where fire or explosion hazards may exist

In electrical and safety engineering, hazardous locations are places where fire or explosion hazards may exist. Sources of such hazards include gases, vapors, dust, fibers, and flyings, which are combustible or flammable. Electrical equipment installed in such locations can provide an ignition source, due to electrical arcing, or high temperatures. Standards and regulations exist to identify such locations, classify the hazards, and design equipment for safe use in such locations.

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<span class="mw-page-title-main">SAE 304 stainless steel</span> Most common stainless steel

SAE 304 stainless steel is the most common stainless steel. The steel contains both chromium and nickel metals as the main non-iron constituents. It is an austenitic stainless steel. It is less electrically and thermally conductive than carbon steel. It is magnetic, but less magnetic than steel. It has a higher corrosion resistance than regular steel and is widely used because of the ease in which it is formed into various shapes.

<span class="mw-page-title-main">Cable entry system</span>

Cable entry systems are used for routing electrical cables, corrugated conduits or pneumatic and hydraulic hoses into switch cabinets, electrical enclosures, control panels and machines or in large heavy-duty vehicles, rolling stock and ships. Possible requirements can be high ingress protection rates or integrated strain relief.

<span class="mw-page-title-main">Electrical conduit</span> Tube used to protect and route electrical wiring in a building or structure

An electrical conduit is a tube used to protect and route electrical wiring in a building or structure. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Most conduit is rigid, but flexible conduit is used for some purposes.

<span class="mw-page-title-main">Gas cabinet</span>

A gas cabinet is a metallic enclosure which is used to provide local exhaust ventilation system for virtually all of the gases used or generated in the semiconductor, solar, MEMS, NANO, solar PV, manufacturing and other advanced technologies.

Telecommunications power cable, as described in Telcordia GR-347 & GR-347, consist of a stranded copper conductor used in AC/DC circuits up to 600 V that are insulated with non-halogen, limited smoke, polyolefin materials that are heat-resistant, moisture-resistant, and flame-retardant. These cables are provided as either Class B (standard) or Class I (flexible) products.

References

  1. "Carbon Steel Enclosures". BisonProfab.com. Retrieved June 9, 2023.
  2. "Stainless Steel Electrical Enclosures Product Reference". Adalet.com. Retrieved June 9, 2023.
  3. "FDS-SMV : Fire Dynamics Simulator - SmokeView". National Institute of Standards and Technology.
  4. Macqueron, Corentin (2017). "Electrical Cabinets Fire Modeling with Fire Dynamics Simulator and CFAST". Research Gate - Groupe de Recherche Feux GDR.
  5. McGrattan, Kevin (2016). "Heat Release Rates of Electrical Enclosure Fires (HELEN-FIRE)". National Institute of Standards and Technology.