Causes of Carbon Brush Failures in Brush Motors of Diesel Generators

With the development of science and technology, the types of motors and their operating conditions have become increasingly diversified. Therefore, various grades of carbon brushes are required to meet these demands, leading to a growing variety of carbon brush types alongside the advancement of the motor industry.

The working principle of a brushed motor involves the commutator and coil as the rotor, with the magnet and carbon brushes as the stator. Although brushed motor technology is quite mature, it has unavoidable drawbacks such as easy wear, high heat generation, low thermal efficiency, and the frequent need to replace carbon brushes.

1. Mechanical Factors

Mechanical factors include: misalignment of the commutator center, unbalanced rotor; excessive vibration of the unit; protruding insulation between commutator segments or protruding commutator segments; uneven or rough grinding of the carbon brush contact surface causing poor contact, surface contamination, unequal air gaps under each commutating pole; uneven or inappropriate spring pressure on the carbon brushes; carbon brushes being too loose in the brush holder causing bouncing, or too tight resulting in jamming. Reducing the unit's operating speed or improving vibration will reduce sparking.

2. Electromagnetic Factors

Electromagnetic factors involve: significant changes in carbon brush sparking when adjusting reactive power or excitation current. Poor contact between carbon brushes and commutator segments during exciter commutation, resulting in excessive contact resistance; uneven thickness of the oxide film on the commutator or slip ring, causing unbalanced current distribution among carbon brushes; sudden load changes or short circuits leading to abnormal voltage distribution between commutator segments; overloading and imbalance of the Dingbo Power genset; unreasonable carbon brush selection and unequal carbon brush spacing.

3. Chemical Factors

Chemical factors include: in a corrosive gas environment or when the unit operates in an oxygen-deficient space, the naturally formed copper oxide film on the contact surface between the commutator and carbon brushes is damaged. The previously established, approximately linear resistance commutation ceases to exist, and commutator sparking intensifies during the re-formation of the oxide film. Excessive dirt accumulation on brush holders and brush racks should be removed with a brush or compressed air.

After learning about the above three factors causing carbon brush failures in diesel generator brushed motors, it is essential to take preventive measures regardless of the factor. Otherwise, even after replacing with new carbon brushes, frequent replacements will be necessary, resulting in excessive wear and tear. Additionally, it is advisable to purchase the original model when buying carbon brushes. It is hoped that the above introduction will provide users with helpful references.

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