Open Machine (Motors)

A machine having ventilating openings which
permit passage of external cooling air over and
around the windings of the machine.
A. Dripproof Machine is an open type machine
in which ventilating openings are so
constructed that successful operation is not
interfered with when drops of liquid or solid
particles strike or enter the enclosure at any
angle from 0 to 15 degrees downward from
vertical.
B. Splashproof Machine is an open type
machine in which ventilating openings are so
constructed 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 degrees
downward from the vertical.
C. Semiguarded Machine is an open machine in
which part of the ventilating openings in the
machine, normally the top half, are guarded
as in the case of a “guarded machine” but the
others are left open.
D. Guarded Machine (NEMA Standard) is an
open machine in which all openings giving
direct access to live metal or rotating parts
(except smooth rotating surfaces) are limited
in size by the structural parts or by the
screens, baffles, grilles, expanded metal or
other means to prevent accidental contact
with hazardous parts. Openings giving direct
access to such live or rotating parts shall not
permit the passage of a cylindrical rod 0.75
inch in diameter.
E. Dripproof Guarded Machine is a dripproof
machine whose ventilating openings are
guarded in accordance with the definition of
a guarded machine.
F. Open Externally Ventilated Machine is one
which is ventilated by means of a separate
motor driven blower mounted on the machine
enclosure. This machine is sometimes known
as a blower-ventilated or a force-ventilated
machine.
G. Open Pipe Ventilated Machine is basically an
open machine except that openings for
admission of ventilating air are so arranged
that inlet ducts or pipes can be connected to
them. Air may be circulated by means
integral with the machine or by means
external to the machine (separately or forced
ventilated).
H. Weather-Protected Machine is an open
enclosure divided into two types:
1. Type 1 enclosures have ventilating
passages constructed to minimize the
entrance of rain, snow, airborne particles
and prevent passage of a 0.75 inch
diameter cylindrical rod.
2. Type 2 enclosures provide additional
protection through the design of their
intake and exhaust ventilating passages.
The passages are so arranged that wind
and airborne particles blown into the
machine can be discharged without
entering directly into the electrical parts of
the machine. Additional baffling is
provided to minimize the possibility of
moisture or dirt being carried inside the
machine.