Cause Of Ignition Of Generator Carbon Brush

 As a sliding contact for conducting current, the carbon brush is used to introduce the excitation current required by the generator into the rotor coil through the slip ring. In order to ensure the normal operation of the motor, the correct selection of brush type is very important. Because of the different raw materials and techniques used in the manufacture of brushes, their technical properties are also different. Therefore, in the selection of brush, should consider the performance of the brush and the requirements of the motor brush.

When the generator is in normal operation, the causes of brush fire are generally as follows:

1. The carbon brush weave is burned.

Carbon brush braids in operation often appear overheating phenomenon, if not handled in time, will lead to braids burned out. But the braids of some generators are covered with insulation, making them hard to find when burned. If it is not found and replaced in time, it will burn out a large number of carbon brushes due to overload, and finally make the generator lose magnetism.

Cause analysis: Due to the unqualified quality of carbon brush, insufficient or uneven pressure of constant pressure spring, mixed use of different types of carbon brush, poor contact between carbon brush and slip ring, brush braid and carbon brush, etc. , carbon brush distribution is not uniform, part of the carbon brush burned because of overload.

2. The carbon brush pulsates incorrectly.

The beating of the carbon brush increases the wear of the carbon brush, resulting in a large amount of carbon powder accumulated in the brush grip, resulting in carbon brush cracking, poor contact between the carbon brush and the slip ring, reduced flow rate, resulting in overload of other carbon brushes。

Cause analysis: The main reason for carbon brush beating is eccentric or rusted slip ring, which needs to be repaired or polished in time.

3. Spark failure between slip ring and carbon brush.

When there is a spark between the slip ring and the carbon brush, if it is not dealt with in time, it will lose the normal working state in the contact process, cause ring fire, burn the carbon brush and brush grip, and even damage the slip ring, resulting in a little grounding.

Cause analysis: There are two reasons for spark between slip ring and carbon brush.

1) Because the carbon brush jumps.

2) Due to the unqualified quality of carbon brush, too low graphite content, too high internal hard impurities, poor contact between carbon brush and slip ring, sparks appear.

4. The slip ring temperature is too high.

Slip ring operating temperature is high for several reasons:

1) Poor contact between carbon brush and slip ring is caused by unqualified quality of carbon brush or insufficient pressure of constant pressure spring.

2) Spark is generated between slip ring and collector ring.

For generators, slip rings and carbon brushes are always weak links. On the one hand, it is the direct contact between the stationary part (carbon brush) and the sliding part, and the transmission current to the rotor winding is the key part of the excitation rectification part, which is affected by a variety of factors. Therefore, the operation and maintenance of carbon brushes and slip rings becomes very important. Generator manufacturers should do the operation and maintenance work well through the following points:

1. Strictly control the carbon brush quality.

Before replacing a carbon brush, check it carefully. Check the appearance of the carbon brush to ensure that it is in good condition.

2. Strictly control the carbon brush replacement process.

When the carbon brush in operation is worn to 2/3 of the height of the carbon brush, replace the carbon brush in time. Before replacing the carbon brush, carefully polish the carbon brush to make its surface smooth and ensure that the carbon brush can move freely up and down within the brush grip. The distance between the lower edge of the brush grip and the working surface of the slip ring should be controlled at 2-3 mm. If the distance is too small, it will collide with the slip ring surface and be easily damaged. If the distance is too large, the carbon brush will easily jump fire and spark. The number of carbon brushes to be replaced at each time should not exceed 10% of the number of carbon brushes at each pole, and a record of carbon brush replacement should be kept. The operator replacing the carbon brush shall stand on the insulation pad and shall not touch the poles or the first stage and the grounding part at the same time, and shall not work at the same time. After the new carbon brush is put into the brush grip, it should be pulled up and down to check whether the carbon brush can move up and down easily. If there is a blockage, the carbon brush should be polished around to meet the requirements.

Guangxi Dingbo Power Equipment Manufacturing Co., Ltd. established in 2006, is an manufacturer of diesel generator in China, which integrates design, supply, commissioning and maintenance of diesel generator set. Product covers Cummins, Perkins, Volvo, Yuchai, Shangchai, Deutz, Ricardo, MTU, Weichai etc. with power range 20kw-3000kw, and become their OEM factory and technology center.