What is an Electrical Enclosure?

What is an Electrical Enclosure?

An electrical enclosure is a housing for electrical or electronic equipment.  Its purpose is to protect that equipment from the environment  and also to protect people from the equipment.

An enclosure protects a Electrical equipments from contaminants in the environment in which it is operating. In addition, the type of enclosure affects the cooling of the equipment.

There is a harmonized European standard that specifies the different aspects of an enclosure’s performance and how it should be categorized – at least for low voltage applications.That is EN 62208 Empty Enclosures for Low-Voltage Switch gear and Control gear Assemblies.

Protection from hazards and the cabinet’s strength

The main hazard from electrical enclosures is usually the electrical components inside.  The job of the enclosure is to prevent people from coming into contact with these components.  If the enclosure is damaged then the electrical equipment and wiring can be exposed and become a shock hazard.

In certain fault conditions, it is possible for live electrical components to touch the body of the enclosure.  For plastic enclosures, made from insulating material, this clearly doesn’t raise an immediate hazard, while the cabinet remains closed.  Metal enclosures should be earth bonded (sometimes to a local earth spike or mat) to protect against this possible hazard.

Protection against water ingress

Classified by the IEC60529 IP code system – the second digit of the IP code.

The enclosure needs to be reasonably watertight to protect from precipitation.  Condensation is also a common problem which can be harder to eradicate since it involves the ingress of water as a vapour.  Flooding is an issue in extreme cases and many enclosures (with high IP ratings) are designed to be submerged in water.

Protection against adverse temperatures

Extreme temperatures can damage electronic equipment or stop it working properly.  Regulating temperature usually involves adding ventilation , double skins, insulation layers or even air conditioning units to the enclosure.

When designing the heat management for an enclosure it is necessary to account for typical external temperature fluctuations and solar gain .  However, the electrical or particularly electronic equipment can generate significant heat inside the cabinet too.

Enclosures are categorized as either open or totally enclosed, and there are  most common types of enclosures are:

Open Drip Proof

Open enclosures permit cooling air to flow through the motor. The rotor has fan blades that help move the air through the motor. One type of open enclosure is the ODP enclosure. In an ODP enclosure, the vent openings prevent liquids and solids that fall from above at angles up to 15° from vertical from entering the interior of the motor and damaging the operating components.

Explosion proof 

Explosion-proof motor enclosures are similar in appearance to TEFC motors, but are designed to contain an inside explosion and to prevent ignition of specified gases or vapors surrounding the motors.

Totally enclosed, fan cooled

Prevents the free exchange of air between the inside and outside of the frame, but does not make the frame completely air tight. A fan is attached to the shaft and pushes air over the frame during its operation to help in the cooling process.

Totally enclosed non ventilated

Sometimes, the air surrounding the motor contains corrosive elements, dust, sand, and other debris that can damage the internal parts of a motor, or the motor is exposed to wind-driven rain or seawater spray. A totally enclosed motor enclosure is not airtight, but it restricts the free exchange of air between the inside of the motor and the outside. A seal where the shaft passes through the housing keeps out water, dust, and other foreign matter that could enter the motor along the shaft. The absence of ventilating openings means that all heat dissipates through the enclosure through conduction.

 

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