The switch vacuum degree tester uses the magnetic control discharge method for measurement.Pull the two contacts of the vacuum switch arc extinguishing chamber apart by a certain distance, apply a high-voltage electric field pulse, place the arc extinguishing chamber inside a solenoid coil or place a new type of electromagnetic coil outside the arc extinguishing chamber, and pass a large current through the coil, thereby generating a pulsed magnetic field synchronized with the high voltage inside the arc extinguishing chamber. In this way, under the action of the pulsed strong magnetic field and strong electric field, the charged ions in the arc extinguishing chamber move in a spiral, and collide with residual gas molecules to cause ionization. The resulting ion current is approximately proportional to the residual gas density, i.e., the vacuum degree.
The vacuum degree tester uses the magnetic control discharge method for measurement. Pull the two contacts of the vacuum switch arc extinguishing chamber apart by a certain distance, apply a high-voltage electric field pulse, place the arc extinguishing chamber inside a solenoid coil or place a new type of electromagnetic coil outside the arc extinguishing chamber, and pass a large current through the coil, thereby generating a pulsed magnetic field synchronized with the high voltage inside the arc extinguishing chamber. In this way, under the action of the pulsed strong magnetic field and strong electric field, the charged ions in the arc extinguishing chamber move in a spiral, and collide with residual gas molecules to cause ionization. The resulting ion current is approximately proportional to the residual gas density, i.e., the vacuum degree. For different vacuum tube models (tube types), due to their different structures, under the same contact gap, same vacuum degree, and same electric and magnetic field conditions, the magnitude of the ion current is also different. Through experiments, the corresponding relationship curves between vacuum degree and ion current for various tube types can be calibrated. After measuring the ion current, the vacuum degree of that tube type can be obtained by querying the ion current-vacuum degree curve for that tube type.
In conventional magnetic control discharge testing of the vacuum degree of the arc extinguishing chamber, in order to improve the test sensitivity, it is necessary to remove the arc extinguishing chamber from the circuit breaker and place it inside the solenoid coil. As a result, when the arc extinguishing chamber is reinstalled into the circuit breaker, mechanical parameters need to be adjusted, which involves a large workload and requires professional personnel. However, using a new type of magnetic control coil can surround the arc extinguishing chamber from the side, so there is no need to disassemble the arc extinguishing chamber. By using a single-chip microcomputer for synchronous control and data acquisition processing, the on-site test sensitivity of the vacuum degree of the arc extinguishing chamber is improved.
2. No need to disassemble the vacuum switch during on-site measurement;
3. Test results are accurate and reliable;
4. Liquid crystal display with Chinese characters, making operation simpler and more convenient;
5. Can save, print, and view test data;
6. The instrument has an RS232 communication interface, which can be connected to a computer to achieve multiple functions such as downloading the vacuum degree-ion current curve and estimating lifespan;
7. Light weight, easy to carry.
8. It realizes the measurement of the vacuum arc extinguishing chamber without disassembly, directly displays the vacuum degree value, enabling users of vacuum circuit breakers to have a detailed understanding of the vacuum state of the arc extinguishing chamber, providing a reliable basis for the planned replacement of the arc extinguishing chamber, providing a strong guarantee for the safe operation of the power grid, and overcoming the defect of the power frequency withstand voltage method which can only judge whether the arc extinguishing chamber is scrapped.
◆ Sampling technology based on ionization charge
The vacuum degree measuring instrument adopts sampling technology based on ionization charge. In the study of magnetic discharge, it is found that when the external excitation power supply, the geometric dimensions of the vacuum arc extinguishing chamber, and the materials used are fixed, the vacuum degree inside the vacuum arc extinguishing chamber has a very accurate corresponding relationship with the amount of ionized charge, while it only has a probabilistic correlation with the peak value of the ionization current. Therefore, the sampling technology based on ionization charge significantly improves the accuracy of vacuum degree measurement of the vacuum arc extinguishing chamber.
◆ Handling of leakage current
When high voltage is applied to both ends of a vacuum arc extinguishing chamber in the open state, there will be a leakage current of several microamps with varying values. Even for vacuum arc extinguishing chambers of the same model, this leakage current has significant individual differences. Especially for vacuum arc extinguishing chambers installed on the complete machine, because the surrounding insulation support parts also have leakage, the total leakage has greater instability and unpredictability, and its value is comparable to the ionization current of a vacuum arc extinguishing chamber with a vacuum degree on the order of 10E-4Pa. By using the method of starting the high voltage twice, the leakage current is deducted.
◆ Built-in
Due to differences in geometric dimensions and materials of vacuum arc extinguishing chambers, when the internal vacuum degree and external excitation power supply are fixed, the discharge charge amount is different and has considerable differences. For accurate measurement, each type of vacuum arc extinguishing chamber must have a corresponding calculation curve from ionization charge amount to vacuum degree.
◆ Perfect input protection circuit
When the vacuum degree of the vacuum arc extinguishing chamber is very low, the vacuum arc extinguishing chamber will be broken down by high voltage during measurement, and the instantaneous high voltage is directly applied to the sampling circuit at the signal input end, subjecting it to a very strong electrical impact. The sampling circuit at the signal input end of the vacuum degree tester is equipped with a complete protection circuit. Even if the instrument temporarily malfunctions due to the high-voltage impact at the input end (it can be restored by restarting), it will not cause damage to the circuit part.
