Brush grades

Brush grades describe the exact composition and the quality of our carbon brushes. With a wide range of formulations and properties, we ensure that the correct carbon brushes are supplied, even for the most special customer requirements.

Thanks to special reworking processes such as impregnation, we can alter and improve the properties of MACK brush grades. For example, we can provide increased strength, improved slide characteristics, or lower spark production.

MACK carbon brushes are divided into five grade categories:

• Carbon graphite grades
• Electrographite carbon grades (high grade)
• Resin-bonded carbon graphite grades
• Copper graphite grades (bronze grades)
• Silver graphite grades

Carbon graphite grades

Our graphite carbon grades consist of different types of graphite. In the process, mineral components provide a weak abrasive effect. At low speed and low sparking they are able to grind off slight carbon deposits on the collector.

The applications

• Machines with a high circumferential speed
• Turbo generators
• Small and medium-sized motors (approximately 30 kW)
• Very small motors
• Universal motors
• Automotive alternators

Electrographite carbon grades (high grade)

Our electrographite carbon grades are produced using annealed and solidified carbon material. The high temperatures during the production transform the carbon into electrographite, which is almost completely free of impurities. Electrographite carbon is characterised by high electrical and thermal loading and also has very good commutation and slide characteristics. There is also a high resistance to short circuits and burn-off. 

The applications

• Direct current motors with any output
• Three-phase AC commutator machinery
• AC machinery
• Drive motors
• Idle power machinery
• Slip rings
• Welding converters
• Universal motors

Resin-bonded carbon graphite grades

Our resin bonded carbon graphite grades represent a further development of conventional graphite carbon grades. This version is characterised by high resistance, high contact voltage, and a large transverse to longitudinal resistance ratio. A further feature is the positive effect on the damping of the commutating currents. 

The applications

• Small and medium-size generators up to 30 kW
• Auxiliary brushes for cross-field excitation
• Three phase AC commutator machinery
• Control motors
• Repulsion motors
• Frequency converter
• Universal motors

Copper graphite grades (bronze grades)

Our bronze carbon grades consist of different types of graphite and metal powders, providing good conductivity together with low contact resistance. The electrical loading capacity is far higher than with graphite and high-grade carbon brushes. 

The applications

• Grounding
• Direct-current, low-voltage machinery
• Automotive starters
• Slip rings
• Synchronised asynchronous motors
• Conductor lines
• Current collectors

Silver graphite grades

Our silver graphite carbon grades are compressed and sintered using a combination of graphite and silver powder. In comparison with bronze carbon grades, they are characterised by an even lower resistance and higher conductivity. 

The applications

• Transmission of measuring, controlling and monitoring information (data transfer)
• Shaft grounding
• Very small motors with low voltage
• Tachogenerators
• Contacts