Original Xi’an Simo Electric Motor Carbon Brushes: High Lubrication, Low Friction, Superior Commutation Performance

These original Xi’an Simo electric motor carbon brushes offer excellent lubrication, low friction coefficients, and reliable commutation. They are ideal for the collector rings of large turbine generators, exciters, hydro generators, and direct current motors with stable commutation.

Overview of Motor Carbon Brushes

Carbon brushes are devices used in motors, generators, and other rotating machinery to transmit energy or signals between the stationary and rotating parts. They are generally made from pure carbon mixed with a binder, often shaped as small blocks fitted within a metal holder. A spring holds them tightly against the rotating shaft. For example, when an oil well is drilled and needs testing, tools are lowered into the well, and carbon brushes transmit signals from the rotating section (steel cable reel) to ground instruments. Carbon brushes resemble pencil erasers with a lead on top, varying in size and widely used in electrical equipment. Common materials include electrographite, resin-impregnated graphite, and metal-based graphite (with copper or silver).

Functions of Carbon Brushes

In brushed motors, the carbon brush presses against the commutator surface, transferring electrical energy to the coil during rotation. Due to its carbon composition, it’s referred to as a carbon brush and is a wear-prone part requiring periodic maintenance, cleaning, and replacement.

Types of Carbon Brushes

Carbon brushes are classified into resin-based, electrochemical, and non-ferrous metal types, each suitable for different motor applications depending on the material and production process.

How to Select High-Performance Carbon Brushes

1. Quickly form a uniform, stable oxide film on the commutator or collector ring.

2. Ensure a long lifespan without damaging the commutator or collector ring.

3. Provide excellent commutation and current-collecting properties to control sparks within allowable limits and minimize energy loss.

4. Operate without overheating, with low noise, reliable assembly, and no breakage.

Carbon Brush Installation

1. The carbon brush should move freely within the holder, with a clearance of 0.1-0.3 mm to avoid excessive shaking. The distance between the holder’s lower edge and the commutator should be around 2 mm.

2. For large or difficult-to-commutate motors, consider dual-type brushes with a lubricated inlet edge and a spark-suppressing outlet edge to improve performance.

3. Uniform pressure should be applied across all brushes in the motor to avoid uneven current distribution, overheating, and sparking. High-speed or vibrating motors may require a higher unit pressure, such as 0.4-0.6 kgf/cm² for traction motor brushes.

Carbon Brush Testing

1. Visually, brushes should be chamfered, well-sized, and structurally sound with appropriate wire gauge and length. They should show no signs of looseness, cracks, or irregularities.

2. Indicators of good performance include:

• Long lifespan without commutator or collector ring wear.

• Good commutation with minimal sparks and low energy loss.

• Low operating noise, no overheating or breakage.

• Quick formation of a stable oxide film on the commutator or collector ring.

3. Testing instruments can verify brush specifications, such as resistance, hardness, density, current density, contact voltage drop, friction coefficient, wear after 50 hours, and permissible peripheral speed.

4. Use the same model and manufacturer’s brushes on a single motor to maintain current distribution. Avoid using different types, as they may lead to uneven current flow, affecting performance.

Carbon Brush Replacement

1. Replace worn brushes all at once to avoid uneven current distribution. For large machinery, replacing all brushes at once may disrupt production; instead, replace 20% of the brushes every 1-2 weeks, allowing for gradual wear-in.

2. Arc brushes for a better fit to the commutator. Place fine sandpaper between the brush and commutator, and grind the brush by rotating the motor. Avoid using emery paper, which can damage the commutator. After grinding, clean with compressed air, wipe off dust, and run the motor at partial load for a few hours, gradually increasing to full load.

Features of Carbon Brushes

Carbon brushes provide conductive contact during sliding motion, unlike metal-on-metal contacts, which could seize or wear heavily. Commonly used in motors, generators, and axle machines, they are essential for commutation and are available in various shapes. Carbon brushes are compatible with AC/DC generators, synchronous motors, battery DC motors, crane motor collector rings, welding machines, and more. As motors and operational environments diversify, the demand for a wide range of carbon brush grades has increased.

Working Principle of Carbon Brushes

1. They transfer external (excitation) current to the rotating rotor (input current).

2. They conduct static charges on the shaft to the ground (ground brush) (output current).

3. They connect the shaft to protection devices, enabling rotor grounding and measuring rotor-to-ground voltages.

4. They reverse current flow (in commutator motors, brushes also aid in commutation).

Carbon brushes are essential for any motor with commutator rings, except for induction-type asynchronous AC motors.