Grade Info

One of the greatest challenges in manufacturing carbon brushes is supplying a grade that will maximize performance for the manner in which the motor or generator is operating. Consideration must be given to the actual running loads, duty cycle, voltage, peripheral speeds, and the environment.

Helwig Carbon’s technical staff is experienced in selecting the proper grade for your application. Choosing the wrong material could cause considerable damage to your equipment. However, overall, grades have been held more accountable for brush performance than is warranted. While selecting the proper grade is crucial, other factors often have a greater effect on brush performance.

Many of the grades used today are derived through variations in raw materials, molding pressure, temperature, duration of the baking process, and after-treatments. All brush grades fall into five categories:

  • Carbon Graphite
  • Graphite
  • Electrographite
  • Copper Graphite
  • Silver Graphite

Each material is designed and developed to perform under certain operating conditions. A best grade for each application is offered, although, several grades with similar characteristics may offer satisfactory performance.

CARBON GRAPHITE

Carbon graphite grades were developed early in the history of motors and generators. These grades, therefore, are found most often on older equipment, particularly those with flush mica commutators. Carbon graphite offers cleaning action for use at slow speeds, low-current densities and medium to low voltages.

ELECTROGRAPHITE

Electrographite is the most common grade used on modern equipment. With excellent performance at high voltages, high-current densities and high speeds, wide ranges of characteristics exist within this category. Most electrographite grades are capable of handling overloads.

GRAPHITE

Graphite grades are used in special applications requiring low-friction characteristics. When brushes must operate at very low current densities or very high peripheral speeds, a graphite grade should be used.

COPPER GRAPHITE

Copper graphite has a material content of 15 – 95% copper or copper alloy. The added conductivity and lower voltage drop, allows metal graphite brushes to operate at very high current densities and low voltages.

SILVER GRAPHITE

Silver graphite has a material content of 8 – 95% silver. The added conductivity and lower voltage drop, allows metal graphite brushes to operate at very high current densities and low voltages.

electrographite, some of our grade information

Grade Data

Many of the grades used today are derived through variations in raw materials, molding pressure, temperature, duration of the baking process, and after-treatments. All brush grades fall into five categories and are represented by the tables below.

Key for Performance Characteristics

Voltage Drop VH 2.5 and Higher H 1.9 to <2.5 M 1.3 to <1.9 L 0.7 to <1.3V VL Less than 0.7V
Coefficient of Friction H 0.3 and Higher M 0.2 to < 0.3 L 0.1 to < 0.2 VL < 0.1
Film Code 1 Mild Abrasive = Light Film 2 No Cleaning - Filming 3 Film Forming Properties = Med - Dark Film
 
VDCFFilmRated Current

Voltage drop, coefficient of friction, film code, and rated current are performance characteristics. Values shown are based on tests under one standard set of conditions, and are for use in comparison between grades only. On any application, the values could vary due to differences in operating conditions.

ResistivityHardnessStrengthRated Current
GradeOHM-INµOHM-MShorePSIN/mm2VDCFFilm #Amp/in2Amp/cm2
H0.00112755300020.7MM1406.2
H2500.00082060670046.2MM1507.8
H3570.00123050280019.3MM1558.5
H4220.0119750360027.9HL1609.3
H9900.00276770430029.6HH1406.2
NH120.03280045302520.1HL1558.5
NH160.0250025220015.2HVL1558.5
NH40.00164045250017.2ML1507.8
ResistivityHardnessStrengthRated Current
GradeOHM-INµOHM-MShorePSIN/mm2VDCFFilm #Amp/in2Amp/cm2
H220.000751845300025.6ML27010.9
H230.00153770450031.0ML17010.9
H240.00164055410026.2ML28012.4
H250.00123065510035.2ML28012.4
H270.00174365390026.9HVL28012.4
H280.00184645260017.9MVL28012.4
H30.00035935350024.1MVL37010.9
H340.00225575440030.3HL28012.4
H350.00225550250017.2HL29014.0
H360.00225570330022.8HVL38012.4
H370.00184670440030.3HVL28012.4
H380.00205080540037.2MVL28012.4
H390.00164085540037.2HVL38012.4
H410.00256260300020.7HVL38012.4
H430.00184665370025.5ML29014.0
H43990.00082045400027.6HL38012.4
H440.00174285550037.9ML28012.4
H44300.00225548250017.2VHL38012.4
H450.00256255330022.8HVL38012.4
H460.00102525150010.3ML28012.4
H470.00256240150010.3HL28012.4
H490.00256245200013.8HL29014.0
H500.00215260290020.0ML29014.0
H510.00225560320022.1MVL28012.4
H520.00225560290020.0HL28012.4
H550.00112750397527.4ML37511.6
H570.00215250260017.9ML29014.0
H5800.00036940370025.5ML19014.0
H600.00215375530036HVL38012.4
H610.00061530150010.3MVL27511.6
H740.00307555180012.4HVL38012.4
H760.00307565240016.6HL38012.4
H770.00266540180012.4HVL38012.4
H820.00164064500034.4ML28012.4
H830.00174270300020.7HL28012.4
H840.00174280550037.9HL28012.4
HH0.00061540300020.7LL17511.6
ResistivityHardnessStrengthRated Current
GradeOHM-INµOHM-MShorePSIN/mm2VDCFFilm #Amp/in2Amp/cm2
H5520.00051215200013.8LL2609.3
H6100.00082020470032.4ML2609.3
H6190.00194735550037.9VHL3507.8
H6210.07177845450031.0VHL3304.7
H6460.0125030500034.5HL1609.3
H6490.009824535260017.9HL26510.1
H6510.0125035430029.6HL2558.5
H7000.00041025230015.9ML17010.9
H7020.00125157004.8MM1609.3
H7040.0006151510006.9ML1609.3
H72400.17425055400027.6VHM2253.9
K0180.000717.740300020.7ML38012.4
K0940.06140037210015.9VHL3304.7
K1740.00820027190013.1HL3558.5
K1940.0037625450031.0HL3558.5
K2140.03588937300020.7VHL2558.5
K2240.00820030400027.6VHVL2558.5
K2440.04102035260017.9VHL2406.2
K2540.0009304035002.0HL28012.4
K2940.02553035200013.8HL2558.5
K3840.01333025250017.2HL3406.2
ResistivityHardnessStrengthRated Current
GradeOhm-inµOhm-mShorePSIN/mm2VDCFFilm#Amp/in2Amp/cm2Metal %
6H60.00059.735250017.2ML1901415
K2750.001333.0225400027.5ML28012.427
6H10.000266.530270018.6ML110015.530
H6710.000256.350600041.3LM111017.130
H43750.00036.623300020.7VLL211017.130
K0750.000266.625400027.5ML210015.530
K1650.00036.625250017.2LL211017.135
6H20.00012330370025.5LL111017.140
H6700.000184.540510035.2LL211017.140
H43330.00015323400027.5VLL213020.240
K0450.000112.825450031ML211017.140
K1750.000164.0645500034.4LL211017.140
K4250.000194.8225500034.4LL110015.542
6H30.000061.825320022.1LL112018.650
K0850.00012.5425330022.8ML112519.350
K5350.0000041.0225500034.4LL211017.153
6H70.0000330.6425340023.4LL113020.265
K1760.0000338.425500034.4LL113020.265
K6760.0000140.3525540037.2LL212018.667
K7360.0000070.1720750051.6LL113020.273
6H80.0000130.3322450031VLL114021.775
H6820.0000050.1325510035.2LVL114021.775
K1360.0000130.3318480033.1VLL114021.775
K2160.000010.25420400027.5LL114021.777.5
K1060.0000040.18615042.4VLL115023.385
K2360.000020.520900062.1LVL115023.385
H6800.0000030.0818930064.1LL115023.387
H6920.0000030.0818880060.7VLL116024.890
K0760.0000200.5131300089.6VLL117527.191
K0860.0000020.057900062.1VLL116024.891
K2860.0000150.3815600041.3LL116024.894
H6930.0000020.06201150080VLL117527.195
ResistivityHardnessStrengthRated Current
GradeOhn-inµOhm-mShorePSIN/mm2VDCFFilm#Amp/in2Amp/cm2Metal %
K2970.000615.24157004.82LL27010.858
K0470.00037.6025450031LL210015.5029
K0170.000051.2720380026.7VLL214021.7050
K0870.000061.5225350024.1VLL313020.1050
K1070.000030.7625650044.78VLL114020.1560
K2270.000041.0125340023.42VLL114020.1560
K0570.0000080.1620550037.9VLL116024.8077
K1970.0000040.1015500034.45VLL117026.3580
K2770.0000020.0510850058.56VLL118027.9088
K0370.0000020.056600041.3VLL120031.0091