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| Common trouble in relay contact control circuit | ||||
| Publisher:admin | Add time：2018/10/30 | Viewed：644 | ||
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1. Maintenance of sensing mechanism For electromagnetic (voltage, current, intermediate) relays, the sensing mechanism is electromagnetic system. The faults of electromagnetic system mainly focus on coil and moving and static core. (1) coil fault maintenance Coil failure usually has coil insulation damage; Formed interturn short circuit or ground by mechanical injury; Because the power supply voltage is too low, the dynamic and static core contact is not close, so that the coil current through the coil is too large, the coil heat to burn. When it is repaired, it should be rewound. If the coil is energized and the armature is not closed, it may be that the outlet connection of the coil falls off, causing the coil to break. Just weld on the exfoliated part after inspection. (2) core fault maintenance The core faults are mainly caused by electrification and the armature can not be absorbed. This may be caused by disconnection of the coil, foreign matter between the moving and static cores, and low power supply voltage. Repairs should be differentiated. After electrification, armature iron noise is big. This may be caused by uneven contact surface of dynamic and static iron cores or by oil pollution. When repairing, remove the coil, file or smooth its contact surface; If there is oil, clean it. The noise may be caused by short circuit or broken ring. Repair or replace the short circuit ring. The armature can not be released immediately after power failure, which may be caused by the moving iron core being stuck, the air gap of the iron core being too small, spring strain and oil on the contact surface of the iron core. During maintenance, the fault shall be treated differently according to the fault cause, or the air gap shall be adjusted to protect it from 0.02 ~ 0.05mm, or the spring shall be replaced, or the oil shall be cleaned with gasoline. For thermal relays, the sensing mechanism is the thermal element. The common fault is the thermal element burning, or the thermal element misoperation and non-operation. (1) the heat element is burnt out. This can be caused by a short circuit at the load side or by the high frequency of thermal elements. The thermal element should be replaced during maintenance and the setting value should be adjusted again. (2) misoperation of thermal elements. This may be caused by the movement due to too small setting value, the movement without overload, or the strong shock and vibration in the use situation, which makes the movement mechanism loose and loose and causes the wrong movement. (3) the thermal element does not work. This may be because the setting value is too small and the thermal element loses its overload protection. Adjust the setting current according to the load working current. 2. Maintenance of the actuator Most relay actuators are contact systems. Through its "on" and "off", to complete a certain control function. The fault of contact system is overheating, wear, welding and so on. The main causes of contact overheating are insufficient capacity, insufficient contact pressure, surface oxidation or cleaning, etc. The main cause of wear is that the contact capacity is too small and the arc temperature is too high, which makes the contact metal oxidize. The main cause of contact welding is high arc temperature, or contact beating. The maintenance sequence of contact is as follows: (1) open the cover and check the contact surface. (2) if the surface of the contact is oxidized, the silver contact can not be repaired. The copper contact can be made smooth with an oil file or the oxide layer on its surface can be scraped gently with a knife. (3) if the contact surface is not clean, use gasoline or carbon tetrachloride to clean. (4) if the contact surface has burn marks and burrs, the silver contact need not be repaired, and the copper contact can be repaired with oil file or knife. Do not use emery cloth or sandpaper to repair, to avoid residual sand, resulting in poor contact. (5) if the contact is welded, the contact shall be replaced. If the contact capacity is too small, the relay with a larger capacity should be replaced. (6) if the contact pressure is insufficient, adjust the spring or change the spring to increase the pressure. If the pressure is still insufficient, the contact should be replaced. 3. Maintenance of intermediate mechanism (1) for air type time relay, among which the inter-mechanism is mainly air bag. Its common trouble is delay is inaccurate. This may be due to the airbag seal is not tight or leakage, so that the action delay is shortened, or even not delay; It could also be that the air passage of the air bag is blocked, making the action delay longer. When repairing, the former should be re-assembled or replaced with a new air bag, while the latter should open the air chamber and clear the plug. (2) for the speed relay, the bakelite swing bar belongs to the intermediate mechanism. If the motor can not brake stop when the reverse connection brake, it may be bakelite swing rod fracture. It should be replaced during maintenance. |
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