Analysis and Countermeasures of abnormal phenomena

Analysis and Countermeasures of abnormal phenomena in the installation and commissioning of mechanical and electrical equipment

after the installation and construction of engineering mechanical and electrical equipment, it is usually necessary to start and debug the motor and its machinery. The commissioning and operation equipment is operated by the personnel of the construction unit and operates for a long time according to the conditions and requirements of formal production or use, which is compared with the requirements of the project design. The purpose is to test the quality of equipment design, manufacturing, installation and commissioning, verify the reliability of continuous operation of the equipment, test the performance of the equipment, compare the test data with the data recorded in the factory of equipment manufacturing, and evaluate the quality of equipment engineering. In actual work, the commissioning of the equipment will encounter unexpected abnormal phenomena, which will cause the motor to trip due to the failure of starting, and there will be more opportunities for motors with larger capacity. In order to facilitate post analysis, we should make preparations before starting the motor (especially for large motors), and analyze the inspection results

2. Inspection and commissioning inspection before starting the motor

timely release the new material industry policy information 2.1 inspection before starting

(1) for newly installed or stopped for more than three months, the nut and flange cover should be reliably fastened, and the insulation resistance between each winding and the ground (shell) of the motor should be measured with a megger, All external wiring on the motor outlet terminal shall be removed before the test. Generally, 500V megger is used to measure the insulation resistance of motors below 500V, and 1000V megger is used to measure the insulation resistance of 500~3000v motors. According to the requirements, the insulation resistance of motors shall not be less than 1 megohm per 1kV working voltage, and the insulation resistance of motors with voltages below 1kV and capacities of 1000 kW and below shall not be less than 0.5 megohm. If the insulation resistance is low, the motor should be dried first, and then the insulation resistance should be measured. Only after it is qualified can it be powered on for use

(2) check whether the secondary circuit wiring is correct. The secondary circuit wiring inspection can simulate the action first without connecting the motor to confirm that all links act correctly, including whether the signal light display is correct. Check whether the connection of the motor outgoing line is correct, whether the phase sequence and rotation direction meet the requirements, whether the grounding or neutral connection is good, and whether the cross-sectional area of the conductor meets the requirements

(3) check whether there are sundries inside the motor, and blow the inside with dry and clean kPa compressed air (you can use a blower or a hand bellows, etc.), but do not damage the winding

(4) check whether the voltage and frequency shown on the motor nameplate are consistent with the voltage and frequency of the connected power supply, whether the power supply voltage is stable (generally, the allowable fluctuation range of power supply voltage is ± 5%), and whether the connection method is the same as that shown on the nameplate. If it is a step-down start, check whether the wiring of the starting equipment is correct

(5) check whether the internal organization of the motor fastening bolts is uniform and loose, whether the bearing is lack of oil, whether the gap between the stator and the rotor is reasonable, whether the gap is clean and whether there are sundries. Check whether there are sundries around the unit that hinder the operation, and whether the foundation of the motor and the driven machinery is firm

(6) check whether the setting value of protective appliances (circuit breakers, fuses, AC contactors, thermal relays, which can carry larger thrusters, etc.) is appropriate. Whether the moving and static contacts are in good contact. Check whether the capacity of the control device is appropriate, whether the melt is intact, whether the specification and capacity meet the requirements, and whether the assembly is firm