Page 71 - Electric Drives and Electromechanical Systems

64 Electric Drives and Electromechanical Systems

The CENELEC and IEC (EN) standards specify the limits on harmonics within the
supply, while the IEEE standards contain recommended practices and requirement tor
harmonic control in electric power system as well as specifying requirements on the user
as well as on the utility. The European Commission document provides a framework for
EMC protection across the European Union.

2.7.5 Protection from the environment

A significant proportion of drive systems have to operate in relatively poor environ-
ments. The first line in this protection is the provision of a suitable protective
enclosure. Two basic classes exist for non-hazardous areas and hazardous areas. An
enclosure for non-hazardous areas is classified by the use of an IP code number
specified in IEC publication 60529 (2013), which indicates the degree of protection
from ingress of solid objects including personnel contact, dust, and liquid. In the
United States, the National Electrical Manufacturers Association (NEMA) classification
should be referred to.
The definitions of the IP classifications are given in Table 2.4. If a drive must operate
in a hazardous environment, where an explosive gas/air mixture is present, the formal
United Kingdom definition is contained in BS EN 60070; careful consideration has to be
given to the design of the enclosure and all external connections. It is recommended that
the designers of systems for this type of environment consult the relevant specialist
agencies, e.g., Health and Safety Agency.

Table 2.4 The IP (internal protection) rating system allows designers to specify a
motor, enclosure, or other components, with a specified degree of protection from
dust, water, and impact. The two numerals can be used to specify the protection
afforded to a component. In a number of cases a third numeral is added, which de-
fines the impact rating of the enclosure.

First number Second number
Protection against solid objects Protection against liquids
0 No protection No protection
1 Objects up to 50.00 mm Protection against falling drops of water
2 Objects up to 12.50 mm Dripping water up 15 degrees from the vertical
3 Objects up to 2.50 mm Direct sprays up 60 degrees from the vertical
4 Objects up to 1.00 mm Water splashed in all direction; limited ingress is
permitted
5 Protection against dust; limited ingress is permitted, Protection from low pressure jets of water in all
but no harmful deposits directions.
6 Totally protected against dust Protection from powerful water jets in all direction
7 Protection from immersion in water up to a depth
between 15 cm and 1 m
8 Immersion under water to a specified depth,
typically 3 m.