Explanation of commutation failure of DC motor commutator

Update:16 Mar 2021

Commutation spark division principle Keeping the brush and commutator in good working condition and maintaining excellent commutation performance are important conditions for ensuring the safety of DC motors. Normally, the motor runs without sparks (or runs with faint harmless sparks), the oxide film on the surface of the commutator is uniform and shiny, and the brush and commutator are slightly worn, etc., which can be considered as a good sign of commutation performance. . On the contrary, strong reversing sparks, damage or abnormality of the oxide film on the surface of the commutator, unstable sliding contact between the brush and the commutator, and abnormal wear of the brush and the commutator are all symptoms of poor commutation. Directly threaten the operation of the motor.

Spark is the arc discharge phenomenon between the brush and the commutator, and it is the most obvious sign of poor commutation of the DC motor. Since a slight brush spark releases weak energy and does not pose a hazard to the operation of the motor, it is called a harmless spark. The energy of a stronger electric brush spark will destroy the sliding contact between the brush and the commutator, burn the mirror surface of the brush and the oxide film on the commutator surface, increase the wear of the two, and cause a vicious circle. This kind of spark is Harmful sparks. What's more, due to the strong brush sparks that free the air on the brush grinding track, the arc flying over causes the ring fire accident to cause huge damage to the motor, posing a threat to the operation of the DC motor. Different reversing sparks have different effects and hazards on the operation of DC motors. In order to determine the impact and hazards of reversing sparks on the operation of DC motors, it is necessary to divide the spark level. The reversing spark is the amount of electromagnetic magnetism released from the reversing element when the brush and the reversing piece are out of contact, which is manifested in the form of arc discharge.

According to the research on the commutation spark, it is a kind of electromagnetic wave with a wide frequency spectrum, the main range of the frequency spectrum is 30KHZ to 1MHZ. The hazard of reversing sparks should be based on the spark energy mark, which can be used as a standard for evaluating reversing sparks. However, due to the complexity and difficulty of spark measurement, spark brightness, intensity and size are usually used as the basis for classifying sparks. Different countries in the world have different standards for spark classification, but all these standards are based on the brightness, intensity, size and damage performance of the commutation sparks to the brushes and commutators. There is a certain instrument that can accurately determine the reversing spark level, which is determined by the observer's visual observation, so it is inevitable that there are certain subjective factors of the spark observer.

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