Switches, disconnectors, switch-disconnectOrS and fuse-combination units
IEC 60947-3-2020 pdf download.LOW-VOLTAGE SWITCHGEAR AND CONTROLG EAR –
Part 3: Switches, disconnectors, switch-disconnectOrS and fuse-combination units.
5.3.6.1 AbIlity to withstand motor switching overload currents See Annex A.
5.3.6.2 Rated making capacity
Subclause 5.3.5.2 of IEC 60947-1:2020 applies with the following additions.
The rated making capacity is stated by reference to the rated operational voltage and rated operational current and to the utilization category according to Table 4.
Not applicable to AC-20 or DC-20 equipment.
5.3.6.3 Rated breaking capacity
Subclause 5.3.5.3 of IEC 60947-1:2020 applies with the following additions.
The rated breaking capacity is stated by reference to the rated operational voltage and rated operational current and to the utilization category according to Table 4.
Not applicable to AC-20 or DC-20 equipment.
5.3.7 Short-circuit characteristics
5.3.7.1 Rated short-time withstand current (I)
The rated short-time withstand current of a switch, a disconnector or a switch-disconnector is the value of short-time withstand current, assigned by the manufacturer, that the equipment can carry without any damage under the test conditions of 9.3.6.2.
The value of the rated short-time withstand current shall be not less than twelve times the maximum rated operational current. The duration of the current shall be 1 s, unless otherwise stated by the manufacturer.
For alternating current, the value of the current is the RMS value of the AC component and it is assumed that the highest peak value likely to occur does not exceed n times this RMS value, the factor n being given by Table 16 of IEC 60947-1:2020.
5.3.7.2 Rated short-circuit making capacity (Icm)
Subclause 5.3.6.2 of IEC 60947-1:2020 applies with the addition of the following note.
Clause 7 of IEC 60947-1:2020 applies with the replacement of the paragraph under the heading wStandard pollution degree of industrial applications: in 7.1.3.2 “Pollution degrees with the following:
Unless otherwise stated by the manufacturer, the equipment is intended for installation under environmental conditions of pollution degree 3.
8 Constructional and performance requirements
8.1 Constructional requirements
8.1.1 General
Subclause 8.1 of IEC 60947-1:2020 applies, with the following additions.
Specific requirements for LV switchgear intended for the connections of aluminium conductors is given in Annex E.
When switches and fuse-combination units coming into the scope of this document are normally used to start, accelerate and/or stop an individual motor, they shall also comply with the additional requirements given in Annex A.
The requirements for single pole operated three-pole switches are included in Annex C.
Auxiliary switches fitted to equipment within the scope of this document shall comply with the
requirements of IEC 60947-5-1.
8.1.2.2 Glow wire testing
Subclause 8.1.2.2 of IEC 60947-1:2020 applies with the following changes and additions.
Parts of insulating material necessary to retain current-carrying parts in position shall conform to the glow-wire tests of 9.2.2.1 of IEC 60947-1:2020 for test temperatures as follows:
— main current carrying parts: 960 C.
— auxiliary current carrying parts: 850 C.
The requirements of 8.1.2.2 of IEC 60947-1:2020 do not apply to parts with a mass lower than 2g (insignificant mass as defined in 3.14 of IEC 60695-2-11:2014). For products containing a plurality of small parts, the total mass of non-tested parts located in close proximity to each other shall not exceed lOg. Proximity shall be based on engineering judgment considering.IEC 60947-3-2020 pdf download.