How to Test Vacuum Contactors?

The vacuum contactor is a switch driven by an electromagnet. Its function is to connect and disconnect the moving contacts and static contacts of the electrical equipment circuit, so as to realize the function of frequently connecting and cutting off the normal working current. It is used in switching break and control circuit. Vacuum contactors can be widely used in industries, power plants, mining, ports and other industries. In order to prove the quality of the vacuum contactor, we can test the vacuum contactor by different methods, and then we will introduce several testing methods for you in detail.

Vacuum detection of the interrupter

The most important part of the high voltage vacuum contactor is the vacuum contact interrupter. In actual operation, safety accidents are often caused by neglecting the vacuum detection of the arc extinguishing chamber and failing to detect the gas leakage of the arc extinguishing chamber in time. Therefore, attention must be paid to the detection of its vacuum degree in daily detection.

In the testing work, it is necessary to strictly test the vacuum degree regularly. When carrying out testing experiments, attention should be paid to separating the vacuum contactor from other electrical components in the high-voltage cabinet.

The specific operation method is:

First, open the whole machine, and then use a clamp to separate the moving contact and static contact in an arc extinguishing chamber to maintain the rated distance, then gradually apply pressure to the two contact ends, and pay attention to maintaining the power frequency voltage at 42 kV.

After one minute of pressurization, if there is no sudden change in the current, it can be considered that the vacuum degree test is qualified. If the current changes, there is a problem and the three phases need to be replaced.

Vacuum contactor wear check

After long-term use of high-voltage motors, the contacts of the internal vacuum contactors will wear out. In addition, the over-travel and synchronism of the vacuum contactor will also change. Therefore, in the daily inspection, it is necessary to strictly record the value of each fine-tuning, and at the same time accurately calculate the cumulative degree of adjustment. When the cumulative value is greater than 3 mm, the arc extinguishing chamber must be replaced in time to ensure the normal operation of the equipment.

The heating condition of the vacuum contactor check

Attention should also be paid to the heat generation of the vacuum contactor during normal operation of the equipment, and at the same time check the interrupting performance of the vacuum contactor when the equipment fails. This detection measures the resistance value of the main contacts when the vacuum contactor (such as is in the closed state. The measurement can use methods such as the voltage drop method, and pay attention to the influence of lead wire and joint resistance on the measurement results. If the resistance value of the main contact is found to exceed 100 micro-ohms during detection, the component should be replaced in time.

Working principle of vacuum contactor

When the electromagnetic coil of the AC vacuum contactor is not energized, the reaction force of the spring and the self-weight of the armature core keep the main contact in the disconnected position.

When the electromagnetic coil is connected to the control voltage through the control circuit, the electromagnetic force overcomes the reaction force of the spring and attracts the armature to the static iron core, driving the main contact to close, the circuit is connected, and the auxiliary contact moves accordingly.

Precautions

During the use period, all parts of the product should be checked regularly, the moving part should not be stuck, and the accessories should not be loose or fall off (if the parts are damaged, they should be replaced in time).

The surface of the contact should always be kept clean and no oil is allowed. When metal beads are formed on the surface of the contact due to the action of the arc, it should be removed in time. When the contact is severely worn, the over-travel should be adjusted in time. When the thickness is only 3/1, the contact should be replaced in time (the black oxide film formed on the surface of the silver and silver-based alloy contacts when the arc is broken， which has a very low contact resistance and will not cause poor contact phenomenon).

The original contactor with an arc extinguishing chamber should be used with the arc extinguishing chamber to avoid short-circuit accidents. The clay arc chute is fragile and should be avoided from collision. If it is broken, it should be replaced in time.

Application of vacuum contact

High-voltage vacuum contactors are usually used together with high-voltage vacuum circuit breakers. It mainly plays the role of turning on and off in the circuit, but its arc-breaking ability is not very strong. So it cannot break the short circuit, but it can operate frequently. The vacuum switch tube is composed of an upper cover, lower cover, metal bellows, and ceramic tube, etc. It has the characteristics of long distance, high mechanical strength, heat resistance, and impact resistance. A pair of dynamic and static contacts are packaged in the vacuum switch tube, and the contact material is made of wear-resistant material, so that under the condition of satisfying the breaking performance, the overvoltage caused by the cut-off during the breaking process is reduced, and the service voltage of the vacuum switch tube is improved.

When the vacuum contactor is closed, the current enters the inside of the vacuum bottle from the contact, forming an arc. When the vacuum contactor is disconnected, the arc is extinguished and the current stops flowing. The closing and opening of the vacuum contactor is very fast, usually only a few milliseconds, so it can be used to protect equipment and people in the power system.