In the safety testing system of electrical equipment, there is a core test for heat resistance of insulating materials — the Ball Pressure Test. It seems simple to operate, but it directly relates to whether electrical equipment will suffer insulation failure due to high temperatures during long-term use, which may further cause electric shock, short circuit or even fire accidents. No matter it is household sockets, power adapters, or the housings of industrial control equipment, all must pass the Ball Pressure Test to ensure safety under rated operating temperature and unexpected high-temperature environments.

1. What is the Ball Pressure Test? What are its core functions?

The Ball Pressure Test is a testing method that simulates the resistance of insulating components of electrical equipment under "mechanical pressure + high-temperature environment".

Its core principle is as follows: Use a steel "ball indenter" with a specified weight (20N) and a specified diameter (5mm) to press on the surface of the tested insulating material. At the same time, raise the temperature of the test environment to the "rated heat resistance temperature" of the material (or the maximum expected temperature of the equipment during normal operation) and maintain it for a certain period (usually 1 hour). After the test, cool it to room temperature. Judge whether the material meets safety requirements by measuring the "indentation diameter" left on the surface of the insulating material. If the indentation diameter does not exceed 2mm, the material’s heat resistance is qualified; otherwise, it is deemed unqualified.

From a safety perspective, the Ball Pressure Test has two core functions:

1). Prevent "thermal deformation failure" of insulating materials: When electrical equipment works, internal components (such as transformers, resistors, chips) generate heat, which increases the temperature of insulating components (such as housings, terminal sheaths). If the insulating material has poor heat resistance, it may undergo severe deformation, even cracks or collapse, under the combined action of temperature, its own weight and external pressure (such as the fixing force during installation). This will further expose internal live components and cause the risk of electric shock to humans.

2). Avoid "fire hazards caused by thermal aging": Poor-quality insulating materials will accelerate aging and soften under high temperatures. They not only lose their insulation protection function but may also decompose to produce flammable substances under high temperatures. Once they come into contact with internal high-temperature components or electric sparks, they can easily cause fires. The Ball Pressure Test simulates extreme working conditions to screen out materials with insufficient heat resistance in advance and eliminate such hazards from the source.

2. Scope of Application of the Ball Pressure Test: Which Products Must Undergo It?

The Ball Pressure Test does not target all electrical products. It focuses on "insulating components" and "non-metallic components that support live parts", covering the following scenarios:

1). Household electrical appliances: Socket housings, plug insulation layers, power cord sheaths of rice cookers, plastic frames of indoor air conditioners, lamp bases, etc.;

2). Information technology equipment: Housings of laptop power adapters, router bodies, terminal covers of printers, etc.;

3). Industrial electrical equipment: Inverter housings, insulation partitions of control cabinets, sheaths of motor junction boxes, etc.;

4) Medical electrical equipment: Housings of medical monitors, insulating components of infusion pumps (which need to meet higher heat resistance standards), etc.

In simple terms, as long as an electrical equipment contains non-metallic insulating components that "need to bear a certain pressure and may be exposed to high temperatures during operation", it must pass the Ball Pressure Test. This requirement is clearly specified in major global electrical safety standards, such as the international standards IEC 60950-1 (Safety of information technology equipment) and IEC 60335-1 (Safety of household and similar electrical appliances), as well as Chinese national standards GB 4943.1 and GB 4706.1.

3. Operation Process of the Ball Pressure Test: Rigor Determines Test Results

The Ball Pressure Test seems to have simple steps, but the parameter control of each link directly affects the accuracy of the results. It must be operated in strict accordance with the standard process, which is divided into 5 steps:

1). Sample Preparation: Ensure Representativeness and Integrity

Cut "representative samples of insulating components" from the product to be tested. The sample size must meet the test requirements (usually a thickness of no less than 3mm and a surface area large enough to accommodate the indentation of the ball indenter). The sample surface must be clean, free of scratches and oil stains to avoid impurities affecting the accuracy of indentation measurement.

2). Test Condition Setting: Precisely Control "Temperature, Pressure, Time"

Set the temperature of the heating chamber according to the product standard requirements. Connect the 5mm-diameter steel ball indenter to a 20N weight, and ensure the ball indenter presses vertically on the sample surface with uniform and stable pressure. When the temperature of the heating chamber stabilizes at the set value, start timing and maintain it for 1 hour.

3). Constant Temperature Maintenance: Simulate Long-Term High-Temperature Working Conditions

During the test, monitor the temperature of the heatig chamber in real time to ensure the temperature fluctuation does not exceed ±2℃, thus avoiding test result deviations caused by unstable temperature. At the same time, ensure the ball indenter keeps in close contact with the sample surface without displacement. If the sample undergoes severe deformation in advance under high temperature, record the deformation as the basis for subsequent judgment.

4). Cooling and Indentation Measurement: The Key "Result Judgment Link"

After the test time ends, immediately take the sample out of the heating chamber and cool it naturally to 23℃±2℃ at room temperature (do not use cold water or other methods for rapid cooling, to avoid material shrinkage affecting the indentation size).Use a measuring tool with an accuracy of no less than 0.01mm (such as a microscope or vernier caliper) to measure the "maximum diameter" of the indentation on the sample surface. Note that the indentation may be circular or elliptical, so user need to measure the diameter of the longest part.Compare with the standard requirements: If the indentation diameter is ≤2mm, the sample is judged as "qualified"; if the diameter is ＞2mm, it is judged as "unqualified", indicating that the material's heat resistance cannot meet the application requirements.

4. Conclusion: A Small Test for Great Safety

As a "basic but crucial" electrical safety test, the Ball Pressure Test seems to only measure a small indentation, but it bears the important responsibility of protecting users' lives and property.For manufacturers, strictly conducting the Ball Pressure Test and selecting insulating materials that meet requirements is a prerequisite for products to be launched in compliance with regulations.For consumers, understanding the significance of the Ball Pressure Test and paying attention to whether electrical products have passed relevant safety certifications (implying the Ball Pressure Test is qualified) when purchasing is an important way to avoid safety risks.

As electrical equipment develops towards "miniaturization and high power", the density of internal components becomes higher, and heat generation increases. This raises higher requirements for the heat resistance of insulating materials. It means the importance of the Ball Pressure Test will become more prominent. Only by adhering to the principle of "not lowering test standards and not simplifying test procedures" can every electrical product be equipped with reliable insulation safety guarantees.