How to test a contactor?

Figure 1: A good contactor.

1.Test steps

We can test the contactor through the following aspects.

1.1 Test The Coil of The Contactor

Check the rated voltage of the contactor coil and connect it to the matching power supply. Open the switch and check whether the contactor is closed. If it cannot be pulled in, it indicates that the contactor coil is faulty.

Another method is to use a multimeter to measure the voltage of the contactor coil. If you have no experience, you can use the parameters of a new contactor with the same power as a reference.

1.2 Test The Contacts of The Contactor

If the contactor can be pulled in and the three-phase power supply is normal, but there is a lack of phase at the output end, we can judge whether it is normal by measuring the voltage of any two phases of three phases. At this time, we need to check the main contact of the contactor to see if it is worn and burned. If yes, the contactor has been damaged, please replace it in time.

Figure 2: Test the contacts of the contactor.

1.3 Contact Electromagnetic Mechanism Suction

Insufficient suction of electromagnetic structure is a common phenomenon. Generally, the contactor can be pulled in, but there is a lack of phase at the lower end of the main contact. After the external force is applied, the missing phase will disappear. This situation also indicates that the contactor has been damaged. Please replace it in time.

2. Matters

Theses are the performance of phase loss of some motors: Increased vibration; Abnormal sound; Temperature rise; Speed drop; Current increases; There is a strong buzzing sound when starting, and it cannot be started.

If the above phenomenon occurs, please focus on checking whether the power supply and contactor are out of phase and replace them in time to avoid greater losses.

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