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Daily maintenance and main function detection of the motor protector

Article Source:Thermal protectorAuthor:YaxunPopularity:Published time:2019-10-21 10:14

Mechanical life and electrical life, if operated improperly or under abnormal conditions, will accelerate the aging of electrical components and shorten the service life of the motor protector. Therefore, whether natural or human factors will inevitably cause malfunctions and affect normal work, the correct use of motor protectors and normal daily maintenance are particularly important. Due to the large number of motor protectors and the complexity of the structure, the specific maintenance methods also have different grades. Here, only the maintenance and precautions that the protector has in common are briefly stated.
First, the maintenance of the motor protector protector includes daily maintenance, process inspection and regular inspection including each inspection before starting. The main job is to maintain according to the actual use of the protector, but there are differences in time and method.
(1) The surface of the protector body should be kept clean, and the surface area is excessively dusty and damp, which can easily lead to a decrease in the overall insulation resistance of the protector and induce a malfunction.

(2) Check if the output of the motor protector, the input terminal, the contact or the connecting plug are in good contact. Is there any phenomenon of overheating, oxidation, damage to the connecting line due to poor contact, especially the poor contact of the three-phase current main circuit or improper selection of the wire diameter to affect the housing.
(3) Check if the display status of the protector indicator light, digital tube and LCD screen is normal.
(4) Check if the protector and connector are installed firmly.
(5) Check whether the current value of the protector has changed from the original set value,
Deviation, especially the operation of the device by using the potentiometer knob and the DIP switch, is easily adjusted by the operator to change the original set value.
(6) Check if the cooling and ventilation system of the motor is blocked, and if there is abnormal noise in the motor running. Whether the insulation value is reduced, whether the AC contactor contacts are damaged, whether there is noise when sucking, etc.

(7) The main function of the motor protector The on-site inspection of the protector is the most practical and feasible method. The initial installation or periodic inspection of the protector plays a crucial role. The basic operation method is as follows:

1. Motor protector overcurrent test
(1) The protector is sent to the rated working power supply, and the protector is displayed and the indication is normal.
(2) The protector setting current value is set to the rated current value of the motor.
(3) Start the motor and check if the motor can start up within the specified time.
(4) After the motor is started, the actual running current of the motor should be checked regardless of whether the motor is running at no load or at the load. The protector without current display can measure the actual running current value of the motor at this time with a clamp-type ammeter.

(5) According to the actual running current value of the motor, select the overcurrent multiple that needs to be tested, and then adjust the setting current value. For example, test 6 times the overload current. If the actual running current of the motor is 30A, set the setting current value to 5A, and use the chronograph to observe whether the protective device operating time meets the specified time of the overcurrent characteristic curve specified in the random specification.
(6) After the protector is protected, it should be observed, inquired, displayed or indicated correctly. Such as fault type, overcurrent value, motor thermal power status, etc.
(7) Check the lockout state after the protector is activated and reset it within the specified time.

2. Phase failure test The phase failure test operation method and procedure are basically the same as the overcurrent test. Manually disconnect any phase power supply before the motor is running or starting, and observe whether the protector operates according to the phase failure protection time of the manual.

3. Protector with protection functions such as over-voltage, under-voltage, leakage, under-current, motor pre-embedded thermal element detection, and simple test on site.

 
(1) If the over- and under-voltage test starts the motor according to the normal procedure, the protector voltage protection function is modified before the motor starts. If the input voltage of the grid input voltage is 400V, the overvoltage protection value is modified to be lower than the grid voltage when the overvoltage is tested (the specific ratio is set according to the manual). When the voltage protection is under test, the voltage protection value is modified to be higher than the grid voltage, and it is observed whether the motor can complete the operation within the set action time range.
(2) The leakage test method is basically the same as the over and under voltage test. The leakage current is made by the artificial method, and a fixed resistor and an adjustable resistor are connected in series in any phase of the motor to observe whether the leakage protection action is completed according to the set action time. In short, on-site field inspections of the main and other functions of the protector can be carried out according to the random instructions.


Second, the precautions when using the protector
(1) After the protector is unpacked, first check whether the product is in a state of damage or defect, and check the random accessories.
(2) Read the product's random instruction manual carefully.
(3) Whether the field conditions in the field are convenient for the installation and wiring of the protector, and whether the protection function mode meets the actual requirements of the motor.
(4) Whether the field environment used is adapted to the working conditions standards specified by the protector.
(5) The user of each input and output terminal of the protector should be correct when wiring, and the wiring or insert should be fixed firmly and the contact is good.
(6) Whether the wire diameter joint used by the main current of the main machine can smoothly pass through the threading hole of the transformer group of the protector.
(7) When the protector is equipped with a transformer, the accuracy and the specified current ratio of the transformer should be in accordance with the range of the set current of the protector. The cross-sectional area of the secondary current conductor of the transformer must meet the maximum current requirement of the secondary current.
(8) When the protector output (relay contact capacity) cannot meet the required capacity of the AC contactor in the control loop, intermediate relay transition control must be added.
(9) The setting principle of the protector setting current value is equal to the rated current value of the motor.
(10) The fixed position of the protector is as easy to install, debug and observe as possible.
(11) The management of the use of the protector must be the responsibility of the professional, and the unrelated personnel must not use it at will.



Motor protector function test