The reason for sparking of the generator brushes: uneven distribution of the load between the carbon brushes
If a small part of the carbon brushes is due to following reasons:
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①The wear is too short;
②The spring pressure is insufficient;
③The braid of the brush is broken;
④The contact surface between the carbon brushes and the collector ring decreases, etc. ; when the load cannot be shared normally, in order to maintain the normal output of the generator, the current density through the other carbon brushes will increase, and the heat generated by the carbon brushes is proportional to the square of the current (Q= I2Rt), causing a sharp increase in temperature, resulting in sparking, this situation is more serious when the device is under full load and the contact surface of the carbon brush wears irregularly, and gradually deteriorates to formr a ring of fire.
Solution:When encountering this situation, personnel should be prepared in time, use a current clamp to measure the current distribution of each carbon brush, and replace the worn elements , hot and short jump brushes. Carbon brushes, and at the same time replace the pressure spring which has been softened by heat. Adjust carbon brushes that are too heavy or too light in a timely manner. The brushes are uniform and align the position with the normal direction of the circumference of the electric ring so that the carbon brushes are in full contact with the commutator ring.
The pressure of each carbon brush on the slip ring must be basically the same and meet the technical requirements of 14.5 N ± 20%/piece (measured with a spring balance).
Preventive measures: try to reduce contact resistance
1 Clean regularlyent
Be sure to clean the brushes, brush holders, brush holders, blow the toner on the surface of the slip ring and in the brush holder, as well as dust and oil around the slip ring with compressed air and wipe it with a clean cloth. Keep brushes, brush holders, slip rings and brushes clean at all times. It is stipulated that the equipment must be purged at least twice a week and at least 4 groups must be removed for inspection and cleaning every week.
Take advantage of downtime to thoroughly clean the device. Use a clean white cloth dipped in alcohol to clean the surface of the slip ring and the carbon powder in the brush holder or wipe the surface of the slip ring. with gasoline to keep it clean and smooth.
2. The slip ring will generate heat and fire during operation, causing pitting on the surface of the slip ring. Once pitting is detected, take the opportunity to stop and polish it if the brush device; has poor contact, it will also be silver. The contact resistance of the slip ring and the brush device is significantly reduced.
3. Take safe operation measures to prevent the bearing from falling oil, causing the slip ring and brush device to be contaminated with a large amount of oil and increasing the contact resistance between the slip ring and the brush.
Reference for the above content: Baidu Encyclopedia - The brush is on fire