PAS 62072:2005 pdf download Natural graphite brush for rotating electrical machinery – Basic characteristics
This PAS applies to brushes for commutators and slip-rings in rotating electrical machinery.
This excludes brushes of electrical appliances such as starters of automobiles and tractorsmicro-appliances for household and tools, appliances for aeronautics and space, and othersoperating in special conditions.
2Normative references
The following referenced documents are indispensable for the application of this documentFor dated references, only the edition cited applies. For undated references, the latest editionof the referenced document (including any amendments) applies
EC 60276， Definitions and nomenclature for carbon brushes, brush-holders, commutatorsand slip-rings
IEC 60413, Test procedures for determining physical properties of brush materials forelectrical machines
EC 60773， Test methods and apparatus for the measurement of the operationalcharacteristics of brushes
Terms and definitions3
For the purposes of this document, the following terms and definitions apply.
3.1 NG brush materialmaterial, which consists of natural graphite mineral with developed crystal structure and abinder able to take appropriate characteristics as brush
3.2 NG brushbrush for commutator and slip-ring made of NG brush material in accordance with IEC 60276Clause 2
4Classification
The NG brushes should be classified in accordance with 4.1 to 4.4.
According to usage
4.1a) commutator brush;
b) slip-ring brush.
4.2According to grade of rotating electrical machinery:a) for d.c.electrical machine;
b) for turbine generator;
c) for hydro generator;
d) for wound-rotor type asynchronous motor.
4.3 According to voltage used:
a) using up to 100 V;
b) using in the range of 100 V to 500 V;
c) using in the range of 5 00 V to 1 000 V;
d) using in the range of 1 000 V to 3 000V.
4.4 According to operating conditions:
a) operating in current above 600 A;
b) operating in peripheral velocity above 60 m/s;
c) operating in vibrating width above 100 µm;
d) operating in ambient temperature above +40 °C;
e) operating in the on-off times per hour above 20;
f) operating in normal condition.
5 Characteristics
5.1 Physical properties
5.1.1 Bulk density
The bulk density of NG brush material should be in the range of 1,2 g/cm 3 to 1,4 g/cm 3 .
5.1.2 Hardness
The hardness of NG brush material should be in the range of 10 to 40 in HR 2,5/3,5.
5.1.3 Resistivity
The resistivity of NG brush material should be in the range of 10 µΩ·m to 80 µΩ·m for commutators and 6 µΩ·m to 12 µΩ·m for slip-rings.
5.1.4 Bending strength
The bending strength of NG brush material should be in the range of 8 MPa to 15 MPa.
5.1.5 Ash
The ash content in NG brush material should be up to 0,5 %.
5.2 Operating characteristics
5.2.1 Total voltage drop
The total voltage drop should be in the range of 2 V to 3 V.
5.2.2 Coefficient of friction
The coefficient of friction should be up to 0,2.

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