The relay is a kind of electrical appliance that controls or protects the task by turning on or off the control circuit according to external input signals such as changes in electrical quantity (voltage, current) or non-electrical quantity (heat, time, speed, etc.) There are three basic parts, namely the sensing mechanism, the intermediate mechanism and the executing mechanism, and the article describes the troubleshooting methods that they produce.
1 Overhaul of sensing mechanism For electromagnetic (voltage, current, intermediate) relays, the sensing mechanism is an electromagnetic system. The faults of the electromagnetic system are mainly concentrated in the coil and the moving and static core parts.
(1) Coil troubleshooting Coil failure is usually caused by damage to coils; short circuit or earthing due to mechanical damage; due to low power supply voltage, static and dynamic iron cores are not tightly contacted, so that the coil current is too large and the coil heats up and burns. . When it is repaired, it should be re-wound. If the armature does not pick up after the coil is energized, it may be that the coil lead-out line is disconnected and the coil is disconnected. Check out the drop off after welding.
(2) Iron core fault repair The main fault of the iron core is that the armature does not suck up after power on. This may be due to a broken coil, foreign matter between the moving and stationary iron cores, and low power supply voltage. Should be repaired in different situations.
After power on, the armature is noisy. This may be due to the fact that the contact surfaces of the moving and static cores are not even or have oil contamination. When repairing, the coil should be removed, flattened or flattened its contact surface; if there is oil, it should be cleaned.
The noise may be caused by a short circuit or a broken ring. Repair or replace the new short circuit ring.
After the power is cut off, the armature cannot be released immediately. This may be caused by the moving iron core being trapped, the air gap of the iron core being too small, the spring straining, and the contact surface of the core being oily. Maintenance should be treated differently for the cause of the fault, or adjust the air gap to protect it at 0.02 ~ 0.05mm, or replace the spring, or use gasoline to clean the oil. For thermal relays, the sensing mechanism is a thermal element. Common faults are burnout of the thermal element or malfunction or failure of the thermal element.
(1) The thermal element is burned out. This may be due to a short circuit on the load side or a high frequency of operation of the thermal element. The thermal element should be replaced during the inspection and the setting value should be readjusted.
(2) The thermal device malfunctions. This may be due to the fact that the setting value is too small, the action is not overloaded, or there is a strong shock and vibration in the use case, which causes the action mechanism to loosen and trip and cause a malfunction.
(3) The thermal element does not operate. This may be due to the fact that the setting value is too small and the thermal element loses its overload protection function. During the overhaul, the setting current should be adjusted according to the load operating current.
2 Overhaul of actuators The actuators of most relays are contact systems. Through its "pass" and "off", to complete certain control functions. Faults in contact systems generally include contact overheating, wear, and welding. The main cause of contact overheating is insufficient capacity, contact pressure is not enough, the surface is oxidized or unclean; the main cause of increased wear is contact capacity is too small, the arc temperature is too high to make contact metal oxidation, etc. The main reason for welding is arc temperature is too high, or the contact is severely beaten. The contact maintenance sequence is as follows:
(1) Open the cover and check the contact surface condition.
(2) If the surface of the contact is oxidized, the silver contact may not be repaired, and the copper contact may be smoothed or lightly scratched with a knife to remove the oxide layer on the surface.
(3) If the contact surface is not clean, it can be cleaned with gasoline or carbon tetrachloride.
(4) If there are burns and singes on the surface of the contacts, the silver contacts may not need to be repaired, and the copper contacts may be repaired with an enamel or a knife. It is not allowed to use abrasive cloth or sandpaper for refurbishment, so as to avoid residual sand grains and cause poor contact.
(5) Contacts If welding, replace the contacts. If the contact capacity is too small, replace the relay with a large capacity.
(6) If the contact pressure is insufficient, adjust the spring or replace the spring to increase the pressure. If the pressure is still not enough, replace the contacts.
3 Overhaul of the intermediate mechanism (1) For air-type time relays, the intermediate mechanism is mainly airbags. The common fault is delay time. This may be due to loose airbag seal or leak, so that the action delay time, or even no delay; may also be airbag air channel blockage, so that the action delay becomes longer. When repairing, the former should be reassembled or replaced with a new one. For the latter, the air chamber should be disassembled to remove the blockage.
(2) For speed relays, the bakelite pendulum is an intermediate mechanism. If the motor can not stop when the brake is reversed, the bakelite pendulum rod may be broken. It should be replaced when overhauled.
1 Overhaul of sensing mechanism For electromagnetic (voltage, current, intermediate) relays, the sensing mechanism is an electromagnetic system. The faults of the electromagnetic system are mainly concentrated in the coil and the moving and static core parts.
(1) Coil troubleshooting Coil failure is usually caused by damage to coils; short circuit or earthing due to mechanical damage; due to low power supply voltage, static and dynamic iron cores are not tightly contacted, so that the coil current is too large and the coil heats up and burns. . When it is repaired, it should be re-wound. If the armature does not pick up after the coil is energized, it may be that the coil lead-out line is disconnected and the coil is disconnected. Check out the drop off after welding.
(2) Iron core fault repair The main fault of the iron core is that the armature does not suck up after power on. This may be due to a broken coil, foreign matter between the moving and stationary iron cores, and low power supply voltage. Should be repaired in different situations.
After power on, the armature is noisy. This may be due to the fact that the contact surfaces of the moving and static cores are not even or have oil contamination. When repairing, the coil should be removed, flattened or flattened its contact surface; if there is oil, it should be cleaned.
The noise may be caused by a short circuit or a broken ring. Repair or replace the new short circuit ring.
After the power is cut off, the armature cannot be released immediately. This may be caused by the moving iron core being trapped, the air gap of the iron core being too small, the spring straining, and the contact surface of the core being oily. Maintenance should be treated differently for the cause of the fault, or adjust the air gap to protect it at 0.02 ~ 0.05mm, or replace the spring, or use gasoline to clean the oil. For thermal relays, the sensing mechanism is a thermal element. Common faults are burnout of the thermal element or malfunction or failure of the thermal element.
(1) The thermal element is burned out. This may be due to a short circuit on the load side or a high frequency of operation of the thermal element. The thermal element should be replaced during the inspection and the setting value should be readjusted.
(2) The thermal device malfunctions. This may be due to the fact that the setting value is too small, the action is not overloaded, or there is a strong shock and vibration in the use case, which causes the action mechanism to loosen and trip and cause a malfunction.
(3) The thermal element does not operate. This may be due to the fact that the setting value is too small and the thermal element loses its overload protection function. During the overhaul, the setting current should be adjusted according to the load operating current.
2 Overhaul of actuators The actuators of most relays are contact systems. Through its "pass" and "off", to complete certain control functions. Faults in contact systems generally include contact overheating, wear, and welding. The main cause of contact overheating is insufficient capacity, contact pressure is not enough, the surface is oxidized or unclean; the main cause of increased wear is contact capacity is too small, the arc temperature is too high to make contact metal oxidation, etc. The main reason for welding is arc temperature is too high, or the contact is severely beaten. The contact maintenance sequence is as follows:
(1) Open the cover and check the contact surface condition.
(2) If the surface of the contact is oxidized, the silver contact may not be repaired, and the copper contact may be smoothed or lightly scratched with a knife to remove the oxide layer on the surface.
(3) If the contact surface is not clean, it can be cleaned with gasoline or carbon tetrachloride.
(4) If there are burns and singes on the surface of the contacts, the silver contacts may not need to be repaired, and the copper contacts may be repaired with an enamel or a knife. It is not allowed to use abrasive cloth or sandpaper for refurbishment, so as to avoid residual sand grains and cause poor contact.
(5) Contacts If welding, replace the contacts. If the contact capacity is too small, replace the relay with a large capacity.
(6) If the contact pressure is insufficient, adjust the spring or replace the spring to increase the pressure. If the pressure is still not enough, replace the contacts.
3 Overhaul of the intermediate mechanism (1) For air-type time relays, the intermediate mechanism is mainly airbags. The common fault is delay time. This may be due to loose airbag seal or leak, so that the action delay time, or even no delay; may also be airbag air channel blockage, so that the action delay becomes longer. When repairing, the former should be reassembled or replaced with a new one. For the latter, the air chamber should be disassembled to remove the blockage.
(2) For speed relays, the bakelite pendulum is an intermediate mechanism. If the motor can not stop when the brake is reversed, the bakelite pendulum rod may be broken. It should be replaced when overhauled.
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