Page 42 - Industrial Power Engineering and Applications Handbook

Theory, performance and constructional features of induction motors 1/23
1.1 5 Degree of protection

The nomenclatures used above to define an enclosure
were earlier interpreted in different ways by different
manufacturers. To achieve harmonization, IEC 60034- 1
has eliminated the use of these codes. Instead, designation
IP, followed by two characteristic numerals according to
IEC 60034-5, is now introduced to define an enclosure.
The first characteristic numeral defines the protection of
personnel from contact with live or moving parts inside
the enclosure and of machines against the ingress of
solid foreign bodies. The second numeral defines the
Squirrel cage rotor type of protection against ingress of water. Tables 1.10
and 1.11 show these requirements.

Table 1.10 Types of protection against contact with live or
moving parts

First Type of protection
characteristic
number as in
IEC 60034-5

No special protection of persons against accidental
or inadvertent contact with live or moving parts
inside the enclosure.
No protection of equipment against ingress of
solid foreign bodies.
Protection against accidental or inadvertent
contact with live and moving parts inside the
enclosure by a larger surface of the human body,
Figure 1.19(a) TEFC squirrel cage motor (Cooling system ICOAI)
(Courtesy: NGEF Ltd) for example a hand, but not against deliberate
access to such parts.
Protection against ingress of large solid foreign
bodies (diameter greater than 50 mm).
Protection against contact with live or moving
parts inside the enclosure by fingers.
Protection against ingress of small solid foreign
bodies (diameter greater than 12 mm).
Protection against contact with live or moving
parts inside the enclosure by tools, wires or objects
having a thickness greater than 2.5 mm.
Slip ring rotor Protection against ingress of small solid foreign
bodies (diameter greater than 2.5 mm).
Protection against contact with live or moving
parts inside the enclosure by tools, wires, or such
objects of thicknesses greater than 1 mm.
Protection against ingress of small solid foreign
bodies (diameter greater than 1 mm) excluding
the ventilation openings (intake and discharge)
and the drain hole of the enclosed machine which
may have degree 2 protection.
Complete protection against contact with live or
moving parts inside the enclosure.
Protection against harmful deposit of dust. The
ingress of duct is not totally prevented, but dust
will not be able to enter in an amount sufficient
to harm the machine.
Figure 1.19(b) TEFC slip ring motor (Cooling system KOA1 Totally dust-tight. No ingress of dust.
(Courtesy: NGEF Ltd)