DC Motor Maintenance

1, commutator maintenance
(1) The surface of the commutator should be kept smooth and form a uniform dark brown glossy oxide film. If the surface of the commutator is stained with toner or oil, use a hand blower to clean it or use a soft cloth stained with alcohol to wipe the surface of the commutator to ensure cleanliness;
(2) When it is found that the surface state of the commutator deteriorates, the spark is large, and there are defects such as rough and uneven, burns, etc., it should be considered to stop the vehicle and polish the surface with "0" fine sandpaper to re-establish the oxide film. If the surface of the commutator is excessively rough, uneven, or partially worn, the commutator should be turned again. When turning, the end of the armature winding and the joint sheet should be covered with paper to avoid the splashing of metal chips. The cutting speed is 2 meters per second, and the cutting depth and feed amount are not more than 0.1mm. After cutting, the commutator piece should be chamfered, and if necessary, the interchip mica should be carved to avoid the mica piece higher than the commutator piece;
(3) Check whether the mica groove is clean, and the corners of the reversing sheet should be smooth without burrs;
(4) Under the condition of ensuring the surface quality of the commutator, it is also necessary to carefully observe and monitor the commutation spark in daily operation. Under normal circumstances, point-like, granular sparks (white or microribbon blue and yellow) are sparsely and evenly distributed on most brushes, and belong to normal commutation sparks. Loud, fireball, or splashing sparks (dark yellow, red, or green) are harmful sparks. When the ring fire spark occurs, the motor should not continue to run.
2, the use of brushes
(1) Blow the toner on the brush, brush box and commutator with air pressure;
(2) Check whether the brush contact arc surface has a burning point, whether the contact surface is uniform and smooth, if there are defects, it should be replaced immediately;
(3) Check whether the brush is flexible in the brush box;
(4) Check whether the pressure of the brush is uniform and appropriate, under normal circumstances, the brush pressure is 15-25kpa, and the pressure of each brush is calculated according to the cross-sectional area of the brush, and then compared 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, and replace it when the brush is worn to 1/3 of the original height. It should be noted that the number of brushes to be replaced at one time should not be too much, and the batch replacement of brushes is easy to destroy the oxide film on the surface of the original commutator. Simply replace short or problematic brushes. On the same motor, it is not allowed to use different grades of brushes, even if the same grade of brushes, because of different manufacturing time, the performance is also significantly different, so it is not allowed to use. After the new brush is installed, it is necessary to use the "0" emery cloth, the back is tightly attached to the commutator, and the brush is ground with the direction of the brush rotation to obtain a good contact surface with the commutator surface. After grinding, remove the toner, and make the motor run at 1/4-- 1/3 rated load for half an hour to one hour, and then increase the load;
(6) Check whether the fixing of the brush braid is reliable, and the uneven vibration and pressure of the brush are easy to cause the uneven distribution of the current of each brush;
(7) Check whether the press foot and spring of the brush box are softened or broken.
3. Motor winding
(1) The insulation resistance of the winding should be measured (with l000V megohm meter) before power transmission, the insulation resistance value should generally not be lower than R=V/ (1000+P/100) (MΩ) value, V is the rated voltage of the motor winding (V), P is the rated power of the motor (kW). But the minimum value is ≥0.5MΩ. If the insulation resistance is low, it should be dried.
(2) Check whether the connection line between the winding and the frame has insulation damage or mutual short circuit;
(3) Pay attention to observe whether the temperature rise of the main pole winding and the commutator pole winding is normal.
4. Maintenance of cooling system
Usually DC motor adopts pipe forced ventilation or air and water circulation cooler two cooling methods, for the air and water circulation cooler cooling method, the cooling device fan due to high speed, often appear burning loss, directly affect the ventilation cooling effect, absolutely can not be ignored.
(1) Daily check whether the filter device in the cooling device is saturated, and whether there is dust blocking on the air supplement filter material;
(2) For the cooling device fan, the dynamic balance test of the fan impeller should be done regularly;
(3) Often check whether the inlet/outlet valve of the cooling device is fully opened, the inlet temperature is less than 33 ° C, and the temperature difference between the cooled gas temperature and the inlet temperature should be > 7 ° C (to ensure that the inlet air temperature is less than 40 ° C).
5. Bearing
Ensure that the grease is equal to about 2/3 of the space in the oil chamber of the bearing cover, and replace the new grease after 2000-2500 hours of work. The grade of the grease is No. 3 lithium base grease, and the grease is replaced at least once a year.
6, other aspects of maintenance
(1) Check whether the conductive ring of the brush holder and its connection are complete, whether the connection screw is loose, and whether the creepage distance to the ground meets the standard requirements;
(2) Check whether the jack at the bottom of the frame is loose;
(3) Check whether the installation of the speed measurement feedback equipment is loose and whether the work is normal during maintenance.