In some chemical plants, there are always some areas that burn down DC contactors. According to my work experience, it is usually caused by the following reasons:
1. The motor starts frequently.
2. The application working temperature is too high, the environmental humidity is too high or the dust is too much (the key reason for burning the AC contactor at this time, the solution: remove and replace the DC contactor with large space), and carefully operate the termination button in the control circuit, whether the self-protection contact point is loose, or the working pressure of the contact point is insufficient. If it is loose, the electromagnetic coil will work The main circuit breaker of DC contactor is easy to burn because of the unstable absorption of transformer core and the transient voltage. In case of frequent burning of AC contactors, and in case of burning of contacts of AC contactors, the key reasons are as follows:
1. The rated voltage of the AC contactor is too small, and the AC contactor shall be effectively equipped according to the rated voltage of the motor.
2. The motor often starts and stops. Due to the frequent starts and stops, the nodes are easily burned by electro-optic, which shortens the service life of the AC contactor.
3. The product quality of AC contactor is poor. Nowadays, the contact volume of some AC contactors is too small, which is inconsistent with the rated voltage indicated. In the whole operation process, the contact overtemperature is caused, which is also very easy to burn the AC contactor.
4. The dynamic contact point of the AC contactor is jammed, which results in the unsmooth posture during operation, and it is very easy to arcing, resulting in the damage of the AC contactor.
5. The connection between the AC contactor and the transmission line is not very good, the screw is not tightened, etc., the over temperature occurs, or the transmission line is too thin, the whole operation process is hot, which will also cause damage to the AC contactor.
6. The arc extinguishing cover of the AC contactor is missing or damaged, resulting in the actual effect of arc extinguishing is not good, which is very easy to damage the AC contactor.
7. The dust around the AC contactor is large and cold, which is very easy to damage the AC contactor.
Manufacturer of AC contactor - if the electromagnetic coil of AC contactor is damaged, the key reasons are as follows:
1. The external working voltage of the electromagnetic coil is inconsistent with the working voltage of the electromagnetic coil of the AC contactor. If the working voltage of the external power supply is too high, it is very easy for the electromagnetic coil to be ablated.
2. The working voltage of the electromagnetic coil is different from that of the external working voltage. For example, the working voltage of the electromagnetic coil is 200V for communication and 200V for direct current.
3. There is dust in the middle of the transformer core of the AC contactor, which makes the iron core of the transformer not absorb in time. The iron core of the transformer is very easy to burn, which causes the temperature of the electromagnetic coil to rise and damages the AC contactor.
4. There is a pyrogen around the AC contactor, which causes the working temperature to be too high and the electromagnetic coil to be easily ablated.
5. The natural environment around the AC contactor is too wet and cold, which makes the insulation layer of the electromagnetic coil not good and easy to be damaged.
AC contactor manufacturer - according to the left and right points, we should distinguish well and do relative solutions.
In addition to frequent start-up, three-phase imbalance and excessive load, there is a long-term lack of maintenance oil for motor bearing (shaft sleeve), which causes less damage and large gap, resulting in the motor operating current exceeding the load current of the AC contactor of the original power circuit, so it is very easy to damage. Check the operation current, and pay attention to regulating the star delta start change time relay.