Overview
The arc resistance tester is a special testing equipment used to evaluate the ability of the surface of insulating materials, especially resin materials, to resist high-voltage arcing. The working principle is to apply a series of phased increased arc voltages between two electrodes at a specified distance on the surface of the material, and quantify the arc resistance of the material by observing and recording the time or voltage phase required for the conductive path or failure to occur on the surface of the material. This test is an important reference value for ensuring the long-term reliability and safety of insulated components in electrical equipment.
Test Principle:
Tests are usually performed under standard atmospheric conditions. A flat resin specimen is placed in a chamber with two tungsten electrodes in contact with the specimen surface at a specific angle and spacing (typically 6.35 mm). According to the preset program, the testing machine generates intermittent high-voltage and low-current arcs between the electrodes. Common test standards, such as IEC 61621 and ASTM D495, specify a graded test method for multiple voltage/current stages from low to high. Arc resistance is usually characterized by the total time (seconds) or the highest stage reached when a continuous conductive path is formed on the surface of the material or significant erosion, carbonization, or combustion occurs.
A key parameter is arc current I, which is related to the applied voltage U and the loop impedance Z, and the basic relationship can be expressed as:
I = U / Z
During the test, the thermal and ionization effects of the arc work together on the resin surface, which can lead to polymer chain breakage and carbide formation, thereby reducing the surface resistance.
Influencing factors
The chemical structure and composition of the resin body are the fundamental factors that determine its arc resistance. In general, resin systems containing aromatic rings, heterocyclic or inorganic fillers exhibit better resistance to arc erosion. The type and content of fillers significantly affect performance, such as aluminum hydroxide, silicon micropowder, etc., which can improve arc resistance by inhibiting the formation of carbonization channels. In addition, the thickness of the specimen, surface finish, pre-treatment conditions (e.g., drying), and the temperature and humidity of the test environment all have a direct impact on the test results.
Testing process
Before testing, resin samples should be prepared according to relevant standards to ensure a clean and flat surface. Securely mount the specimen on the grounding platform of the chamber and adjust the electrode position precisely. After starting the device, the program automatically controls the arc application and interval time of each test stage. The operator needs to monitor the surface condition of the specimen through the observation window or sensor. When a stable conductive path is formed on the surface of the specimen (current continues to flow for more than a specified time) or when there is a failure phenomenon defined by the standard, the test is automatically terminated and the device records and outputs the total arc time.
Interpretation of the results
The higher the arc resistance time value obtained by the test, the stronger the resin material's ability to resist arc damage. This data is an important basis for material research and development, quality control and selection. For example, in electrical switches, circuit breakers, insulators and other equipment, there are clear requirements for the arc resistance of resin insulation components. This test allows for the comparison of the performance differences of different formulations of resins, the optimization of material design, and the prediction of their service life under long-term arc stress, thereby ensuring the electrical safety of the end product.
Key parameters and typical requirements
| Test current range | 10 mA to 40 mA |
| Electrode spacing | 6.35 ± 0.05 mm |
| The angle of the electrode to the specimen | 35° (Typical) |
| Arc on-off period | For example, 1/4 s passes, 3/4 s breaks |
| Typical test endpoint criterion | Continuous conductive pathways are formed on the surface |
| Common performance ratings | Divided according to the total time tolerated |
Notes:
The operation of the arc resistance tester requires strict adherence to the safety specifications of high-voltage equipment. Reliable grounding must be confirmed before the test and fully discharged after the test. The cleanliness and wear status of the electrodes should be checked and maintained regularly to avoid affecting arc stability and test repeatability. For the same batch of material, it is recommended to test multiple specimens to obtain statistically significant results. The test report should clearly record the test standards, environmental conditions, sample information and specific failure phenomena.
References
IEC 61621, Dry, solid insulating materials - Resistance test to high-voltage, low-current arc discharges.
ASTM D495, Standard Test Method for High-Voltage, Low-Current, Dry Arc Resistance of Solid Electrical Insulation.