How is a temperature rise test conducted?

Temperature rise testing is a crucial method for evaluating the temperature increase of electrical equipment and electronic components under operating conditions. The results directly impact the product's safety, reliability, and lifespan. By simulating actual operating conditions and measuring temperature changes, this method effectively determines whether the product meets design standards and regulatory requirements. The following sections will provide a detailed explanation covering test equipment, test samples, and the testing process.

1. Test Equipment

Temperature rise testing requires various equipment working together to ensure a controllable test environment

and accurate temperature measurement.  The main components include:

1.1 Temperature and Humidity Chamber: This simulates the ambient temperature and humidity conditions

under which the product operates. It can precisely control the temperature (typically -40°C to 150°C)

and relative humidity (10% to 98% RH) within the chamber, providing a stable environment for testing.

1.2 Power Supply/Load Source: This provides the appropriate voltage, current, or power input according to the

type of test sample (e.g., connectors, wiring harnesses, structural components, charging cables,

electronic modules, etc.), simulating the actual operating load.

The power range must cover the rated power of the test sample.

1.3 Temperature Measurement Instruments:

Thermocouples: Common types include K-type and T-type.

They have a fast response time and a wide measurement range (-50°C to 260°C).

They can be directly attached to the surface or critical internal parts of the sample to accurately collect temperature data.

1.4 Infrared Thermometer: Suitable for measuring the surface temperature of samples that are difficult to access. 

It does not require direct contact with the sample and can quickly obtain the temperature distribution over a large area.

However, its measurement accuracy is significantly affected by environmental factors (such as dust and radiation).

1.5 Data Acquisition System: Connected to thermocouples or other temperature sensors,

it can real-time collect and record temperature data from multiple points. It supports data storage and export for

subsequent analysis. The sampling frequency is usually adjustable (e.g., 1 time/second to 10 times/second).

2. Test Samples

The selection of test samples should be based on the test objectives and product characteristics.

Common test samples include:

2.1 Connectors: such as charging plugs, wiring harnesses, connector components, and busbars.

These components generate Joule heat due to current flow, leading to temperature increases.

2.2 Electronic components: such as resistors, capacitors, inductors, diodes, transistors, and integrated circuits.

Temperature increases in these components can affect their performance parameters (e.g., resistance, capacitance,

amplification factor) and may even cause damage.

2.3 Cables and connectors: such as power cables, communication cables, and plugs/sockets.

Cables and connectors generate heat during current transmission; excessive temperature can lead to insulation aging,

short circuits, and other failures.

Test samples must meet the following requirements: no damage or deformation to the external appearance;

electrical performance in accordance with factory standards; and no prior destructive testing or repair,

to ensure the accuracy and representativeness of the test results.

3. Test Procedure

3.1 Sample Pre-treatment: Place the test sample in a standard environment (temperature 25℃±5℃,

relative humidity 50%±10% RH) for at least 2 hours to allow the sample temperature to equilibrate with the

ambient temperature, minimizing the impact of initial temperature on the test results.

3.2 Test Preparation:

Check that all test equipment is functioning correctly. Calibrate temperature measurement instruments,

power supplies, etc., to ensure measurement accuracy meets requirements.

3.3 Determine the temperature measurement points according to the sample structure and test requirements.

Typically, measurement points are located on heat-generating parts (such as motor windings, transformer cores,

and electronic component pins), heat dissipation surfaces, and critical functional areas. 

At least one thermocouple should be placed at each measurement point and securely fixed with high-temperature tape.

3.4 Place the test sample in the temperature and humidity chamber. Connect the power supply, load box,

and data acquisition system, ensuring correct and secure wiring to avoid poor contact, measurement errors, or safety hazards.

Initial Parameter Measurement: With the sample unpowered, measure and record the initial temperature at each

measurement point, as well as the sample's insulation resistance, as baseline data.

3.5 Apply Load and Monitor Temperature:

Apply the rated load (or specified test load) to the sample using the power supply and load box, according to the

test standard or product technical requirements, and start the sample to its normal operating state.

3.6 Simultaneously start the temperature and humidity chamber, setting it to the sample's operating environment

conditions (e.g., 40℃ temperature, 60% RH).  Start the data acquisition system to record the temperature changes

at each measurement point in real time. Set the sampling interval according to the test requirements (e.g., 1 minute/cycle).

3.7 During the test, closely observe the sample's operating status. If any abnormal sounds, smoke, or sparks occur,

immediately stop the test and investigate the cause of the malfunction.

3.8 Thermal Stability: Continuously monitor the sample temperature. When the temperature change at each

measurement point is less than 2℃ within 1 hour, the sample is considered to have reached thermal stability.

Record the temperature values at this time as the stable temperature rise of the sample. 3.9 Test Termination and

Parameter Measurement: Disconnect the power supply to the sample, stop applying the load, and after the sample

temperature has dropped to near ambient temperature, measure and record parameters such as insulation resistance,

and compare these values with the initial parameters.

3.10 Data Processing and Result Analysis: Organize the temperature data recorded during the test, calculate the

temperature rise at each measurement point (temperature rise = final temperature - initial temperature),

and compare these values with the temperature rise limits specified in the product standard or design requirements

to determine if the sample meets the requirements. Simultaneously, analyze the temperature distribution to evaluate

the sample's heat dissipation performance and heat distribution uniformity.

By strictly adhering to the above requirements for test equipment, test sample standards, and test procedures,

the accuracy and reliability of the temperature rise test results can be ensured, providing important data for

product design improvement, quality control, and safety assessment.