Reasons and Solutions for Sparks in Generator Brushes

  1.The current density of the electric brush is too high.In actual operation,if two brushes are stuck due to mechanical reasons,insufficient spring pressure,and other reasons that do not output power,in order to maintain normal load,the current passing through other brushes will increase.If there is a brush that is rubbed and deviated in the increased current passing brush,the contact area with the sliding ring will decrease,and the current density of the contact surface will increase.According to Q=I*IRT,the heat generated is proportional to the square of the current.When the accumulated heat cannot be dissipated,the temperature rises sharply and sparks are generated at the contact surface between the brush and the slip ring.In addition,the generation of sparks makes the working environment of the brushes worse,leading to a vicious cycle and more severe sparking of the brushes.When this situation is severe,ring fires can occur.
  2.Uneven or unsatisfactory brush pressure.When the electric brush leaves the factory,the manufacturer has relevant regulations:the pressure of the electric brush is adjusted to a pressure that does not produce sparks.After scientific demonstration and practical summary,the pressure is generally 200-300µ/c㎡,which is 0.02-0.03 MPa.It is required that the pressure between each electric brush should also be uniform,and the difference should not exceed 10.If a certain brush friction is too short or the brush is stuck in the brush frame during long-term operation of the generator,the pressure will be uneven.In addition,due to factors such as mechanical and spring softening due to heating,the pressure cannot meet the theoretical requirement of the brush not producing sparks.When we tighten and pull carbon brushes,sometimes we rely on intuition and lack experience accumulation,resulting in significant operational errors.
  3.The surface of the electric brush is not clean.This is something that is overlooked.The brushes of the normally operating generator are sealed in a closed cabinet,and there is a gear shaped axial flow fan between the two brushes,which rotates by the rotor to timely remove the heat generated by the ground graphite carbon powder and brushes,achieving the purpose of cleaning and cooling.If the cabinet door is not tightly closed or forgotten to close during inspection,the dust outside will be sucked into the brush with hot air and attached to the brush column,which will affect the heat dissipation of the brush.On the other hand,when sparks occur on the electric brush,the surface of the brush posts is not clean,and the strength between the edges of the brush posts is not strong enough,which can easily cause ring fire.In addition,the slip ring on the car has spiral grooves,which is to increase the heat dissipation area of the brush,improve contact with the brush,make the brush more fully cooled,and make it easier for the carbon powder to be removed.If the cabinet door is not tightly closed and the fan suction is insufficient,dust outside can easily adhere to the spiral groove,and the consequences can be imagined.Considering that the excitation electromechanical brush is exposed to the outside due to its relatively low voltage,it is also recommended to conduct regular maintenance and cleaning.A few days ago,there was an incident in our factory where the excitation electric brush emitted sparks and was forced to shut down.The reasons were multifaceted,and small things often led to big disasters.We should pay enough attention to it.
  4.The bearing vibrates greatly.The second phase of the main shaft is equipped with an exciter,and due to the long bearings and many additional equipment,it is naturally difficult to control the vibration,.The prolonged operation of the machine,fatigue,aging and other complex factors cause increased bearing vibration.With the vibration of the electric brush,uneven friction of the brush column,loose leads and springs will occur,and local sparks will slowly progress,affecting the overall situation.