High-Voltage Vacuum Contactor Testing and Maintenance Guide: Troubleshooting and Practical Tips

High-voltage vacuum contactors are currently widely used in various power equipment and other high-voltage motor equipment in China. The integrity and operating status of this component are crucial to the overall operation and safety of the machinery and equipment. Therefore, relevant inspection and maintenance personnel must carefully check this component in daily work, promptly identify problems, and conduct regular maintenance to ensure the normal progress of production.

1. Principles for Inspection and Maintenance of High-Voltage Vacuum Contactors

The inspection and maintenance of high-voltage vacuum contactors should be carried out regularly to form a systematic and standardized operating procedure. For key items, in addition to daily patrol and maintenance, key inspection items and locations should be checked and maintained at regular intervals. Problems identified during daily inspections should be repaired or replaced in a timely manner to ensure the safe operation of the machinery and equipment. At the same time, maintenance personnel should also enhance their awareness of safe operation in daily work, standardize operations, and avoid safety accidents.

2. Items and Methods for Inspection and Maintenance of High-Voltage Vacuum Contactors

2.1 Pay Attention to the Detection of Vacuum Degree in Vacuum Contact Tip Arc-Extinguishing Chamber During Inspection

The most important component in a high-voltage vacuum contactor is the vacuum contact tip arc-extinguishing chamber. In practical operation, safety accidents often occur because the detection of the vacuum degree of the arc-extinguishing chamber is neglected, and air leakage in the arc-extinguishing chamber is not detected in time. Therefore, great attention must be paid to the detection of its vacuum degree during daily inspections.

In the detection work, a 42 kV power frequency withstand voltage operation within a unit minute can be adopted to strictly detect the vacuum degree regularly. When conducting the detection test, it is necessary to separate the vacuum contactor from other electrical components in the high-voltage cabinet. The specific operation method is as follows:

First, open the brake of the entire machine.

Then, use a fixture to pull apart the moving contact and static contact in one arc-extinguishing chamber, keeping them at the rated test opening distance.

Gradually apply voltage to the two contact ends, and ensure that the power frequency voltage is maintained at 42 kV.

After applying the voltage for one minute, if there is no sudden change in the current, the vacuum degree detection can be considered qualified. If the current changes, it indicates a problem, and the three phases need to be replaced.

2.2 Pay Attention to Checking the Wear Condition of the Vacuum Contactor During Inspection and Maintenance

After long-term use of the high-voltage motor, the contacts of the internal vacuum contactor will wear out. In addition, the overtravel and synchronization of the vacuum contactor will also change. Therefore, during daily inspections, the fine-tuning values of each time must be recorded strictly, and the cumulative degree of adjustment must be accurately calculated. When the cumulative value exceeds 3 mm, the arc-extinguishing chamber must be replaced in a timely manner to ensure the normal operation of the equipment.

During inspection and maintenance, attention should also be paid to checking the heating condition of the vacuum contactor when the equipment is working normally, and the interruption performance of the vacuum contactor when the equipment fails. For this kind of inspection, the resistance value of the main contact when the vacuum contactor is in the closed state should be measured. The voltage drop method can be used for measurement, and attention should be paid to the influence of lead and joint resistance on the measurement results. If the resistance value of the main contact exceeds 100 microohms during detection, the component should be replaced in a timely manner. A comprehensive maintenance of the vacuum contactor can be carried out every six months to correct the overtravel and synchronization of the vacuum contactor.

2.3 Pay Attention to Detecting the Voltage Value of the Vacuum Contactor During Inspection and Maintenance

This detection mainly focuses on checking the pull-in voltage and release voltage. Generally, a voltage regulator can be used for testing, and a multimeter can be used for real-time monitoring. During the detection, close attention should be paid to observing whether the contactor can complete the pull-in when the control voltage is 3/4 of the rated voltage, and whether the vacuum contactor can be disconnected when the voltage drops below 1/3 of the rated voltage. If a problem occurs, necessary repairs should be made to the component.

2.4 Pay Attention to Measuring the Insulation Resistance During Inspection and Maintenance

For the main circuit, the insulation degree between phases and between phases and the ground is required to be the same as the vacuum degree. This detection can also be carried out simultaneously with the vacuum degree detection. When detecting the main circuit, a 2500-volt megohmmeter can be used to measure the insulation resistance. If the measured value exceeds 500 MΩ, it can be regarded as normal; if the value is lower than this standard, maintenance work should be carried out in a timely manner. For the auxiliary circuit, a 500-volt megohmmeter can also be used for simultaneous monitoring during daily inspections. If the measured value is lower than 1 MΩ, the circuit needs to be repaired or replaced.

2.5 Pay Attention to Detecting the Electrical Components in the High-Voltage Cabinet During Inspection and Maintenance

High-voltage varistors and high-voltage capacitors are usually installed in parallel at the output end of the vacuum contactor to absorb the overvoltage generated during equipment operation and prevent damage to the equipment. Therefore, when inspecting the vacuum contactor, attention should also be paid to detecting the resistors and capacitors in the high-voltage cabinet.

2.5.1 Detection of High-Voltage Varistors

To detect the varistor, a DC voltage can be applied to the two terminals of the resistor, and the current can be controlled at 1 mA. At this moment, if the measured resistance value is about 11 kΩ (with an error not exceeding 0.5 kΩ), the varistor can be regarded as normal; if the error increases, the component should be replaced and maintained in a timely manner.

2.5.2 Detection of High-Voltage Capacitors

A certain voltage (which should be a stable DC voltage) can be applied to the varistor, and the current of the component can be measured under this voltage. If the current value exceeds 30 mA, the component should be maintained or replaced in a timely manner.

2.6 Other Items That Should Be Paid Attention to in Inspection and Maintenance

In addition to conducting detection tests on necessary values during inspection and maintenance, attention should also be paid to the maintenance of the hardware equipment of the high-voltage vacuum contactor.

Every time the high-voltage vacuum contactor is inspected, attention should be paid to keeping the vacuum arc-extinguishing chamber and other electrical components in the high-voltage cabinet dry, and cleaning and maintenance should be carried out on each component. At the same time, an appropriate amount of lubricant can be added to the parts that are prone to wear during the operation of the vacuum contactor to reduce the wear degree of the components and ensure the normal operation of the machinery and equipment.

In addition to the main contacts, other auxiliary contacts of the vacuum contactor should also be checked. The scope of inspection should include checking whether the contact surface is clean and dry, whether there is component damage, and testing the contact pressure. At the same time, for the moving and static contacts, the overtravel degree, the deformation coefficient of the spring, and the stiffness coefficient of the spring should also be detected. Other items, such as whether the machinery and equipment are on a horizontal working surface and whether the welding between various components is stable, should also be checked during daily inspection and maintenance.

3. Conclusion

The operating status of the high-voltage vacuum contactor directly affects the normal operation of the entire motor equipment. Therefore, maintenance personnel must be responsible in the inspection work, inspect each component of the vacuum contactor one by one, and promptly repair the problems found. At the same time, the inspection and maintenance work should be institutionalized, standards and rules should be established, and regular inspections should be carried out to do a good job in the daily maintenance of the equipment, ensure the safe operation of the equipment, and ensure the normal development of production activities.