Precautions for daily maintenance of DC motor

DC motor maintenance generally requires:

1. Environmental conditions of DC motor:

(1) No water vapor, corrosive gas such as acid or alkaline, or combustible gas such as gas, and dirt such as dust are allowed to enter the room where the motor with protection grade of IP23 or below is installed;

(2) During continuous operation under rated load, the ambient air temperature shall not be more than 40 ℃, not less than 5 ℃, and the relative humidity shall not be more than 90%;

2. Regular general inspection during operation

(1) Keep the outer surface of the motor and its surrounding environment clean, and do not place anything on or inside the motor;

(2) Whether the motor foot is fastened to the foundation, and whether there is abnormal sound or vibration during operation;

(3) Whether the ventilation window has smooth air;

(4) Whether there is constant time overload;

(5) Whether the grounding device is reliable;

3. Regular maintenance and inspection

(1) For the DC motor that operates frequently, the following inspections shall be carried out regularly, at least once a month;

(2) Under the rated load, there shall be no spark greater than level 1 on the commutator;

(3) Check whether the surface of the commutator is smooth and clean. If there is any mechanical damage or spark burn mark, handle it according to the "maintenance of commutator" standard;

(4) Check whether the brush is excessively worn and whether the pressure of the brush holder is appropriate;

(5) Blow the dust and brush powder inside the motor with compressed air of no more than two atmospheres, and wipe the dust and scale on the surface;

(6) Remove all wiring connected with the motor, and measure the insulation resistance of the winding to the housing with a 500V megohmmeter. If it is less than 1 megohm, it shall be subject to "drying of insulation"

(7) When the motor is running, measure the temperature of the bearing and listen to its rotating sound. If there is any abnormal sound or the temperature rise exceeds, handle according to the standard of "bearing maintenance";

(8) If the motor has to be stopped for a long time, the commutator shall be wrapped with paper and the whole motor shall be covered with anti cloth to ensure that the temperature of the motor storage place is not less than 5 degrees, not more than 40 degrees, and the relative humidity is not more than 90%, and there shall be no water vapor and corrosive gas intrusion.

Maintenance requirements for main components of DC motor:

1. Maintenance of commutator

(1) The commutator surface shall be smooth and form a uniform dark brown and glossy oxide film. If the surface of the commutator is stained with carbon powder and oil stain, the surface of the commutator shall be cleaned by hand blower or by soft cloth stained with alcohol to ensure cleanness;

(2) When it is found that the surface condition of commutator deteriorates, sparks are large, rough, out of round, burn and other defects, it is necessary to stop the commutator and polish its surface with "0" fine sandpaper to rebuild the oxide film. If the surface of the commutator is excessively rough, out of round or some parts are excessively worn, the commutator shall be turned again. During turning, the end of armature winding and joint piece shall be wrapped with paper to avoid splashing of metal scraps. The cutting speed is 2 meters per second, and the cutting depth and feed rate are not more than 0.1mm. After cutting, chamfering shall be conducted between reversing pieces, and mica shall be carved between pieces if necessary to avoid mica piece higher than reversing piece;

(3) Check if the mica groove is clean, and the edges and corners of the reversing plate shall be smooth without burr;

(4) Under the condition of ensuring the surface quality of commutator, it is also necessary to carefully observe and monitor the commutator spark in daily operation. In general, spot and granular sparks (white or micro blue and yellow) are distributed sparsely and evenly on most brushes, which belong to normal commutation sparks. The sound, fireball or splash sparks (dark yellow, red or green) are harmful sparks. When the ring fire spark occurs, the motor should not continue to run.

Use of brush

(1) Clean the carbon powder on the brush, brush box and commutator with air compressor;

(2) Check whether the brush contact arc surface has burning point, whether the contact surface is uniform and smooth, and replace it immediately if there is any defect;

(3) Check whether the electric brush floats flexibly in the brush box;

(4) Check whether the pressure of the electric brush is uniform and appropriate. Generally, the pressure of the electric brush is 15-25kpa. Calculate the pressure of each electric brush according to the sectional area of the electric brush, and then compare it with the actual measured pressure. Regardless of the length of the brush, its pressure should meet the requirements;

(5) Check the wear height of the brush. When the brush is worn to 1 / 3 of the original height, it should be replaced. It should be noted that the number of brushes to be replaced at one time should not be too much, and the replacement of brushes in batches is easy to damage the oxide film on the surface of the original commutator. Just replace the short or faulty brush. In the same motor, it is not allowed to use brushes of different brands. Even if the brushes of the same brand have obvious differences in performance due to different manufacturing time, they are not allowed to be used. After the new brush is installed, it is required to use "0" abrasive cloth, and the back of the brush is closely attached to the commutator. Grind the brush along the rotation direction of the brush to obtain a good contact surface with the commutator surface. After grinding, remove the carbon powder and run the motor for half an hour to an hour under 1 / 4-1 / 3 rated load, then increase the load;

（6） Check whether the fixation of the brush braid is reliable, and whether the current distribution of each brush is uneven due to the vibration and uneven pressure of the brush; (7) check whether the pressure foot and spring of the brush box are softened or broken.

Motor winding

(1) Before power transmission, the insulation resistance of the winding shall be measured (with l000v megger). Generally, the insulation resistance value shall not be lower than the value of R = V / (1000 + P / 100) (m Ω). V is the rated voltage of the motor winding (V), P is the rated power of the motor (kw). But the minimum value is ≥ 0.5m Ω. If the measured insulation resistance is low, it shall be dried;

(2) Check whether the connecting wires between the winding and the base have insulation damage or mutual short circuit;

(3) Observe whether the temperature rise of main pole winding and reversing pole winding is normal.