Arc Resistance Tester for Plastic Parts

Method Essentials This method uses power-frequency high voltage and low current to generate intermittent arc discharges between two electrodes on the surface of solid insulating materials (the intermittent arc procedure is shown in Table 1). By gradually shortening the arc interruption time and then increasing the arc current, the material is subjected to progressively severe arcing conditions, thereby distinguishing the material's arc resistance. The total time from the initiation of the arc until material failure is recorded.
Electrode Setup: The electrodes should be positioned on a plane perpendicular to the sample surface and tilted at a 35° angle to the horizontal (thus, the axes of the two electrodes form a 110° angle between them). The short axis of the elliptical tip of the electrodes should be horizontal, with the elliptical surface facing the sample. The distance between the tips of the two electrodes should be 6.0 ± 0.1 mm (see Figure 2).
Some organic insulating materials exhibit flame-like behavior under arc action. Even if no obvious conductive path is formed on the material surface, it should be considered as failure.
GB 1411-1978 High Voltage, Low Current Intermittent Arc Resistance Test Method for Solid Electrical Insulating Materials
When applying high voltage to the test specimen, increase it slowly; do not apply sudden voltage changes.
Before each use, carefully check that the grounding wire is intact. Only proceed with power application after ensuring its integrity.
Current-limiting resistors R, R, R, R. Adjust R1. (5) AC milliammeter mA, range 0–50 mA, accuracy class 1.0 or higher.
Common failure modes of materials include:
During measurement, if a discharge tube lights up, the power must be cut off immediately.
A thin conductive path forms between the two electrodes on the material surface, accompanied by a noticeable change in arc sound, bright arc light, and immediate arc extinction.
Number of Samples: Not less than 3. Electrodes are made from crack-free and damage-free tungsten rods, with a diameter of 2.5 mm and a length of about 20 mm. One end of each electrode is ground to form an elliptical surface at a 30° angle to the axis. The tungsten electrodes are welded onto another metal rod with a length L of about 40 mm and a diameter φ of about 8 mm (see Figure 1).
Electrode Cleaning: Clean the electrodes every 10 test points. Wipe the electrode tips with a silk cloth soaked in ethanol. If the electrodes are heavily soiled, use 600-grit sandpaper to remove the contamination. Under 15x magnification, the electrode tips should show no burrs, edge irregularities, deformation, or cracks.
During testing, operators must concentrate fully. Prepare all necessary arrangements before starting. The testing area should be clearly marked or enclosed with metal barriers to indicate a high-voltage danger zone and prevent unauthorized entry.
Materials may crack and fail under arc action.
Samples should be flat, smooth, and free of defects. Sample shape and dimensions: Generally flat samples, square with side length 100 ± 1 mm, or circular with diameter 100 ± 1 mm, thickness typically 2–4 mm. For paint film samples, the film should be uniformly coated on 3240 epoxy-phenolic glass cloth boards. The film thickness should be 0.10–0.12 mm or as specified by the product standard.
To avoid external influences during testing, the electrodes should be enclosed in a glass cover with ventilation holes. If there is no air movement in the test environment and no arc drift occurs, the cover may be omitted.
Note: For some materials, the electrodes easily become soiled during testing. Clean the electrodes after every few test points.
Air-core inductor L; Together with the protective resistor R, it suppresses parasitic high-frequency components in the arc circuit. The total inductance is approximately 1.2–1.5 Henry.
Synchronous motor D drives the normally open contacts Civ, C, Cr at a speed of 30 revolutions per minute to generate the initial three arc procedures as shown in Table 1. K6 is its control switch.

Note: Resistor values and power ratings should be selected based on the transformer used. Reference values are provided in Appendix Section 2.
A conductive path forms due to sufficient carbonization on the surface.
Scope This method is suitable for comparing the arc resistance of solid electrical insulating materials but is not applicable to materials that do not exhibit surface failure under this method. Results obtained with this method cannot be directly compared with those from high voltage high current, low voltage low current, or low voltage high current arc actions.
Before measuring the test specimen, perform a high-voltage test to ensure no noise, ionization, or other phenomena occur at the bridge operating voltage. Only then proceed with testing (if the specimen has already undergone high-voltage testing, this step may not be necessary for every measurement).
High-voltage switch K is a single-pole single-throw switch capable of withstanding 15 kV, operated by a sufficiently long insulated handle to switch on or off.
This international standard describes a test method that can preliminarily distinguish the damage resistance of similar insulating materials under high-voltage, low-current arc discharges near their surface. The discharge causes localized thermal and chemical decomposition and erosion, eventually forming a conductive path on the insulating material. The severity of the test conditions gradually increases: initially, low-current arc discharges are repeatedly interrupted, while in the later stages, the arc current is increased step by step. Due to the convenience of this test method and its short duration, it is suitable for preliminary screening of raw materials, assessing the impact of formulation changes, and quality control testing. Past experience has shown that reproducibility is acceptable for thermosetting materials. When testing thermoplastics, some laboratories have reported unacceptably large variations in results, leading to the recommendation that thermoplastics not be tested. Note: During testing, attempts to reduce variability in thermoplastic test results include controlling electrode pressure and penetration depth into the material. Without such electrode control, testing many thermoplastics may not be sufficiently meaningful. In general, this test method does not allow conclusions to be drawn about the relative arc resistance ratings of materials that may be affected by other types of arcs. Material ratings may differ from those in wet tracking tests (such as IEC 60112, IEC 60587, and IEC 61302) and may also differ from their performance in service, where the intensity, repetition frequency, and duration of arc discharges vary significantly.
The schematic diagram of the arc resistance equipment is shown in Figure 3. The main components of the equipment are as follows:
Some inorganic insulating materials become conductive and incandescent under arc action but regain insulation properties after cooling.