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    1.  Thermal relay fault solution

    –  For false action  :

    –  Ambient temperature problem  : If the ambient temperature is too high resulting in thermal relay misoperation, you can improve its installation environment. For example, install a thermal relay in a well-ventilated place with a relatively stable temperature, or install a cooling device to reduce the temperature around it.

    –  Starting time is too long  : For the motor starting time is too long, it is necessary to adjust the starting mode. It can be used to reduce the starting current and shorten the starting time by step-down starting or soft starting. At the same time, adjust the setting value of the thermal relay properly, so that it can distinguish the normal motor starting current and overload current.

    –  For no action  :

    –  Setting problem  : Re-check and adjust the setting value of the thermal relay. According to the rated current of the motor and the actual working situation, the setting value can be correctly set according to the instruction manual of the thermal relay. The general setting value should be slightly higher than the rated current of the motor, usually 1.05-1.2 times the rated current.

    –  Aging problem of bimetal sheet  : If aging of bimetal sheet is suspected, a new thermal relay needs to be replaced. Because the bimetal plate aging, its action characteristics are difficult to return to the normal state, will affect the reliability of overload protection.

    1.  Fuse fault solution

    –  For false fuse  :

    –  Melt selection problem  : Re-select the melt with the appropriate rated current. The selection of melt rated current should take into account the starting current and normal operating current of the motor. For general motors, the melt rated current can be selected according to the rated current of the motor 1.5-2.5 times (the specific multiple is determined according to the starting characteristics of the motor and other factors).

    –  Melt damage  : If the melt is mechanically damaged during installation, a new melt should be replaced, and care should be taken to avoid damage to the melt during installation. When installing, it is necessary to ensure that the contact between the melt and the fuse is good, and that the melt cannot be twisted, squeezed, etc.

    –  For non-fuse  :

    –  Rated current problem  : Check whether the rated current of the melt is selected too large. If so, it should be replaced with a melt with a suitable current rating. The appropriate melt current rating can be determined by reference to the motor’s rated current and overload multiple.

    –  Poor contact problem  : For poor contact of the fuse contact, clean and tighten the contact. The contact surface can be lightly sanded to remove the oxide layer, and then the contact can be tightened to ensure good electrical contact. At the same time, check whether the connection line of the fuse is firm to avoid increasing the contact resistance due to loosening of the line.

    1.  Electronic overload protector fault solution

    –  For false alarms  :

    –  Electromagnetic interference problem  : Shielding measures can be taken for electronic overload protectors subject to electromagnetic interference. For example, use a shielded wire to connect a current transformer to an electronic circuit, or install an electronic overload protector in a cabinet with electromagnetic shielding. At the same time, check whether there are large electromagnetic interference sources around, such as high-power frequency converters, and try to stay away from these interference sources.

    –  Parameter setting problem  : Re-check and adjust the parameters of the electronic overload protector. According to the rated current, starting current and overload characteristics of the motor, set the overload current threshold, operation time and other parameters reasonably. You can refer to the technical data of the motor and the manual of the protector to set up.

    –  For inaccurate detection  :

    –  Current transformer fault  : If the current transformer fails, such as winding short circuit or open circuit, need to replace a new current transformer. After replacement, it is calibrated to ensure that it accurately converts the main current proportionally to a small current signal.

    –  Electronic circuit component damage  : For the filter, amplification and other components in the electronic circuit damage, the need to use professional electronic equipment for detection and maintenance. Tools such as an oscilloscope can be used to check the signal waveform in the circuit, identify damaged components and replace them. At the same time, pay attention to the quality and compatibility of electronic components to ensure that the replaced components can work normally.

    1.  Other common fault solutions

    –  Wiring fault solution  :

    – If the cable is loose, check the terminal regularly and tighten the loose cable. Use appropriate tools, such as screwdrivers and crimpers, to ensure that cables are securely connected. At the same time, the wiring should be in accordance with the correct wiring mode to avoid wiring errors. If a wiring error is found, correct it in time and connect the cables correctly according to the wiring diagram of the protection device.

    –  Power failure Solution  :

    – If the power supply voltage is too low or fluctuates too much, voltage regulation measures should be taken. A voltage regulator can be installed to stabilize the supply voltage, ensuring that it is within the rated voltage range of the protection device and the motor. For the case of unbalanced three-phase power supply, check whether the load distribution of the three-phase power supply is uniform. If the imbalance is caused by excessive load in a certain phase, the load distribution can be adjusted to balance the three-phase current as much as possible.