The failure of the thermal relay generally has the phenomenon that the thermal component burns out, malfunctions, and does not move.
(1) The thermal element is blown. When the operating frequency of the thermal relay is too high, a short circuit or excessive current is generated on the load side, causing the thermal element to blow. To eliminate this fault, first cut off the power supply, check the circuit to eliminate the short-circuit fault, then re-select the appropriate thermal relay and re-adjust the set value.
(2) The thermal relay malfunctions. The reason for this kind of failure is that the setting value is too small, so that it is not overloaded; the motor starting time is too long, so that the thermal relay may trip during the starting process; the operating frequency is too high, so that the thermal relay is often affected by the starting current. The strong impact and vibration of the place are used to make the thermal relay action mechanism loose and trip; in addition, if the connecting wire is too thin, the thermal relay may malfunction. For the above fault phenomenon, the thermal relay suitable for the above work should be exchanged, and the setting value should be adjusted reasonably or the appropriate connecting wire should be replaced.
(3) The thermal relay does not operate. Since the thermal element is blown or dropped, the current setting value is too large, so that the overload does not operate for a long time; the guide plate is tripped; the connection line is too thick, and the thermal relay does not operate, so the motor is not protected. For the above reasons, targeted repairs can be performed. In addition, after the thermal relay is tripped, it cannot be manually reset immediately. It should be 2 min. After the bimetal is cooled, the contacts are reset.
2.3 Time relay fault repair
The air-type time relay's airbag is damaged or the seal is not tight and leaks, so that the delay action time is shortened or even no delay; the air chamber is extremely clean, and if the dust enters the airway, the air passage will be blocked during the disassembly process. The delay time of the time relay will become very long. In response to the above situation, the air chamber can be disassembled, the rubber film can be replaced or the dust can be removed to solve the problem. The air type time relay will be affected by the change of the ambient temperature and the long-term storage will have a delay time change, which can be adjusted according to the specific situation.
2.4 Speed ​​relay failure and maintenance
After the speed relay fails, it is generally indicated that when the motor is stopped, the brake cannot be stopped. If the fault is not in contact with the contact, it may be caused by improper adjustment of the adjusting screw or breakage of the bakelite pendulum. Just remove the rear cover of the speed relay for inspection.
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