METHODS OF COOLING AND ENCLOSURE OF MOTORS AND GENERATORS (NEMA) BASICS AND TUTORIALS

The machine is provided with an enclosure to give physical protection from external sources of motor damage. The following standard enclosures have been adopted by NEMA:

• Open enclosure: An enclosure with ventilating openings that permits passage of external cooling air over and around the windings of the machine.

• Drip-proof enclosure: An open enclosure in which ventilating openings are so constructed that successful operating is not interfered with when drops of liquid or solid particles strike or enter the enclosure at any angle from 0° to 15° downward from the vertical.

• Splash-proof enclosure: An open enclosure in which ventilating openings are constructed so that successful operation is not interfered with when drops of liquid or solid particles strike or enter the enclosure at any angle not greater than 100° downward from the vertical.

• Guarded enclosure: An open enclosure in which all openings giving direct access to live metal or rotating parts are limited in size by structural parts or by screens, baffles, grilles, or other means to prevent accidental contact with hazardous parts.

• Externally ventilated enclosure: An open closure that is ventilated by a separate motor-driven blower mounted on the enclosure.

• Pipe-ventilated enclosure: An open enclosure with provision for connecting inlet ducts or pipes. It is called force-ventilated when the air through the enclosure is driven by an external blower.

• Weather-protected type 1 enclosure: An open enclosure with ventilating passages constructed and arranged to minimize the entrance of rain, snow, and airborne particles to the live and rotating parts.

• Weather-protected type 2 enclosure: An open enclosure with ventilating passages at both intake and discharge constructed and arranged to permit high-velocity air and airborne particles to be discharged without entering the internal ventilating passages of the enclosure. Motors and Generators 555

• Totally enclosed enclosure: This enclosure prevents free exchange of air between the inside and outside of the enclosure. This enclosure is not airtight.

• Totally enclosed nonventilated enclosure: An enclosure that is not equipped for cooling by means external to the enclosing parts.

• Totally enclosed fan-cooled enclosure: An enclosure that is equipped for exterior cooling by means of a fan or fans integral with the enclosure but external to the enclosing parts.

• Explosion-proof enclosure: A totally enclosed enclosure designed and constructed to withstand an explosion of a specified gas or vapor that may occur within it and to prevent the ignition of gas or vapor surrounding the machine by sparks.

• Dust-ignition-proof enclosure: A totally enclosed enclosure constructed in a manner to exclude ignitable amounts of dust or amounts that might affect the performance or rating, and which will not permit heat, arcs, or sparks liberated inside the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specific dust on or in the vicinity of the enclosure.

• Waterproof enclosure: A totally enclosed enclosure so constructed that it will exclude water coming externally from a hose. Leakage around the shaft is allowed provided it does not enter the oil reservoir. A check valve or drain is provided at the lowest part of the enclosure for drainage.

• Totally enclosed pipe-ventilated enclosure: A totally enclosed enclosure except for openings arranged for inlet and out-ducts or pipes for connection to the enclosed for admission and discharge of ventilating air.

• Totally enclosed water-cooled enclosure: A totally enclosed enclosure cooled by circulating water or water pipes coming in direct contact with the motor parts.

• Totally enclosed water–air-cooled enclosure: A totally enclosed enclosure cooled by circulating air, which in turn is cooled by circulating water, the heat exchanger medium.

• Totally enclosed air–air-cooled enclosure: A totally enclosed enclosure cooled by circulating internal air through heat exchangers, which, in turn, are cooled by circulating external air.

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