Maintenance and upkeep of electric motors
1、 Hengli Electric Motor Maintenance
1. Pre start inspection
(1) Check whether the grounding of the motor and starting equipment is reliable and complete, whether the wiring is correct, and whether the contact is good;
(2) Check if the voltage and frequency indicated on the motor nameplate match the power supply voltage and frequency;
(3) For newly installed or long-term out of service motors (out of service for more than 3 months), the insulation resistance of the winding relative to phase and relative to ground should be checked before starting (measured with a 1000V megohmmeter). The insulation resistance of motors below 500V should generally be greater than 0.5M Ω. If it is lower than this value, the winding needs to be dried;
(4) For wound rotors, it is necessary to check whether the electric brushes and brush lifting devices on the collector ring are working properly, and whether the electric brush pressure meets the requirements. The pressure of the electric brush should be 1.5~2.5 N/cm2;
(5) Check whether the motor rotates flexibly, whether the lubricating oil in the rolling bearings reaches the specified measurement, and whether the oil in the bearings reaches the specified oil level;
(6) Check whether the rated current of the fuse used in the motor meets the requirements;
(7) Check if all fastening bolts and installation bolts of the motor are tightened.
After all the above inspections meet the requirements, the motor can be started. After starting the motor, run it without load for about 30 minutes. Pay attention to whether there are any abnormal phenomena in the motor. If abnormal conditions such as noise, vibration, and heating are found, measures should be taken until the situation is eliminated before it can be put into operation. When starting a wound rotor asynchronous motor, the starting rheostat should be connected to the rotor circuit. For motors with electric brush lifting structures, the electric brush should be lowered, the short-circuit device should be disconnected, the stator circuit should be closed, and the variable resistor should be turned. When the motor approaches the rated speed, lift the electric brush, close the short-circuit device, and the motor starts completely.
2. Maintenance during operation
(1) The temperature rise of Hengli motor during normal operation should not exceed the allowable limit, and the temperature rise of each part should be monitored regularly during operation.
(2) Monitor the load current of the electric motor. When an electric motor malfunctions, it often causes a significant increase in stator current, leading to overheating of the motor. Electric motors with higher power should be equipped with an ammeter to monitor the load current of the motor. The load of the electric motor should not exceed the rated current value specified on the nameplate. Otherwise, the cause must be identified and measures taken to eliminate the adverse conditions before continuing to operate.
(3) Monitor changes in power supply voltage, frequency, and voltage imbalance. Excessive or insufficient power supply voltage and frequency, as well as current imbalance caused by three-phase voltage imbalance, can all lead to motor overheating or other abnormal phenomena.
(4) Pay attention to the odor, vibration, and noise of the electric motor. The winding will emit insulation burning smell due to high temperature. Some faults, especially mechanical faults, can quickly manifest as vibrations and noise. Therefore, when smelling a burnt smell or detecting abnormal vibrations, rubbing sounds, loud buzzing sounds, or other noises, power should be immediately cut off for inspection.
(5) Regularly check the heating and oil leakage of bearings, and replace lubricating oil regularly. Generally, when replacing lubricating oil, the bearings and bearing covers are cleaned with kerosene, and then cleaned with gasoline. For rolling bearings, the lubricating grease should not exceed 70% of the bearing chamber volume.
(6) For winding rotor asynchronous motors, the contact between the brushes and the collector ring, brush wear, and spark conditions should be checked. If the spark is severe, it is necessary to clean the surface of the collector ring in a timely manner and correct the pressure of the brush spring.
(7) Pay attention to keeping the interior of the motor clean, and do not allow water droplets, oil stains, or debris to fall into the interior of the motor. The air inlet and outlet of the electric motor must be kept unobstructed.
Hengli electric motors should undergo regular maintenance after operation, generally divided into two types: minor repairs and major repairs. Minor repairs are general maintenance and do not involve major disassembly of the motor starting equipment and its overall structure. They occur approximately once a quarter. Overhaul involves disassembling all transmission devices and motor components, and conducting a comprehensive inspection and cleaning of the disassembled parts, usually once a year.
