Page 147 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

MAINTENANCE OF MOTORS

8.2 CHAPTER EIGHT

Totally enclosed, fan-cooled. Motors with exterior surfaces are cooled by an external
fan on the motor shaft. Cooling is dependent upon motor speed.
Totally enclosed air-over in-line. Motors with an external fan are driven by a constant-
speed ac motor flange mounted to the motor fan shroud. These provide cooling inde-
pendent of motor speeds. Brakes and tachometers cannot be mounted on the motor
end bracket, except for specific small tachometers which can be nested between the
motor bracket and fan.
Totally enclosed air-over piggyback. Motors have a top-mounted, ac motor-driven
blower with shroud to direct ventilating air over the motor frame.
Totally enclosed dual-cooled air-to-air heat exchanger. Motors are cooled by circu-
lating internal air through the heat exchanger by an ac motor-driven blower. External air
circulated through the heat exchanger by another ac motor-driven blower removes heat
from the circulating internal air. No free exchange of air occurs between the inside and
outside of the motor.
Totally enclosed dual-cooled with air-to-water heat exchanger. This is similar to the
previous description except that external circulating airflow is replaced by user-supplied
water to remove heat from the heat exchanger.
Totally enclosed pipe-ventilated or totally enclosed separately ventilated. Motors are
cooled by user-supplied air which is piped into the machines and ducted out of the
machines by user-supplied ducts.
Explosion-proof. The enclosures of these motors are designed and constructed to
withstand an explosion of a specified gas or vapor which may occur within them. It
prevents the ignition of the specified gas or vapor surrounding the machines by
sparks, flashes, or explosions of the specified gas or vapor which may occur within
the machine casing.
Dust-ignition-proof. The enclosures of these motors are designed and constructed so
as to exclude ignitable amounts of dust or amounts which might affect performance or
rating. It will not permit arcs, sparks, or heat otherwise generated or liberated inside the
enclosure to cause ignition of exterior accumulations or atmosphere-suspended dust on
or in the vicinity of the enclosure.
Weather-protected. These motors are divided into two types, I and II. A type I
motor is open, with ventilating passages constructed to minimize the ability of rain,
snow, and airborne particles to come in contact with the electric parts. A type II
motor includes ventilating passages at both intake and discharge in an arrangement
so that high-velocity air and particles blown into the machine by storms or winds can
be discharged without entering the internal ventilating passages leading directly to
the motor’s electric parts.
Totally enclosed, pipe-ventilated. These motors are totally enclosed except for openings
so arranged that inlet and outlet pipes are connected to them for the admission and dis-
charge of ventilating air. The air may be circulated by means integral with the motor or
external to and not a part of the motor, or separately forced ventilation.
Totally enclosed water, air-cooled. A totally enclosed motor is cooled by circulating
air, which, in turn, is cooled by circulating water. The motor is provided with a water-
cooled heat exchanger for cooling ventilating air and with a fan or fans, integral with or
separate from the rotor shaft, for circulating ventilating air.
Totally enclosed air-to-air cooled. This totally enclosed motor is cooled by circulating
internal air through a heat exchanger, which is cooled by circulating external air.

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