Exploring What Is A Bulk Current Injection?: A Deep Understanding of the Working Principles and Applications of Bulk Current Injection Test System（BCI）

What Is A Bulk Current Injection:

High current injection is a testing technique in automotive electronics used to verify whether a product will experience functional degradation or exceed tolerance limits when subjected to electromagnetic interference of different frequency ranges. This test is commonly encountered in EMC testing for automotive electronics, as in actual vehicle scenarios, the connecting cables for different onboard components are often bundled together.

This leads to the coupling of electromagnetic interference signals of different frequencies, which in extreme cases, can result in failure of the affected components, posing a risk to the safety of the vehicle. Hence, the purpose of high current injection testing is to simulate the injection of RF signals onto the power or signal lines of the product being tested in order to verify whether its function will degrade or its performance indicators will remain within tolerance limits.

High current injection testing is a commonly used method and has widespread applications in electromagnetic compatibility (EMC) laboratories. It is mainly used to measure the EMI/RFI disturbance characteristics of devices in the high frequency to ultra-high frequency range. In practical applications, high current injection testing can be used to evaluate the relative compatibility between equipment and other electronic devices or systems. It does so by injecting high voltage and high frequency currents onto cables to simulate electromagnetic coupling between devices and determine the equipment’s resistance to interference.

Principle of Bulk Current Injection Test System（BCI）:

The principle of Bulk Current Injection Test System（BCI） is based on the use of current injection probes. During the test, the current injection clamp acts as the first current transformer, and the cable harness acts as the second current transformer. After coupling with the RF interference signals, the RF current flows in common mode through the cable harness. These currents flow in the same direction in all the cables of the tested device and then return to the device’s connection port through the reference ground. This method is called common mode current injection (CBCI) and is suitable for high-frequency testing (30MHz~400MHz). Another method is to flow in differential mode, where currents return to the device’s connection port through cables other than the ones being tested. This method is called differential mode current injection (DBCI) and is suitable for low-frequency testing (0.1MHz ~30MHz). The current monitoring clamp acts as a device for measuring cable currents, and it monitors the actual induced current value in real-time.

The basic principle of high current injection testing involves the following aspects:

1. Choosing the Appropriate Test Current:

When conducting high current injection testing, we should choose a test current larger than the rated working current of the circuit based on factors such as circuit design requirements, rated load current, and operating environment. This ensures the sufficiency of the test and effectively prevents damage to the circuit.

2. Determining the Test Duration:

Test duration refers to the time during which high current is injected into the circuit. In determining the test duration, it is necessary to consider the circuit’s thermal dissipation ability to prevent overheating and damage to the circuit. Generally, the test duration can be determined based on the circuit’s heat dissipation design and the highest operating temperature.

3. Controlling the Test Environment:

High current injection testing needs to be conducted under appropriate environmental conditions. This includes ensuring the stability and accuracy of the test equipment and controlling environmental parameters such as temperature and humidity around the circuit. Only when the test is conducted in a stable environment can accurate and reliable test results be obtained.

High current injection testing generally involves the following steps:

1. Equipment Preparation:

First, prepare the necessary testing equipment, such as a high current injection power supply, measuring instruments, etc., to ensure that the equipment is functioning properly and calibrated.

2. Circuit Connection:

Connect the circuit to be tested with the testing equipment, ensuring a firm and reliable connection. For high-frequency and high-voltage circuits, attention should be paid to relevant protection and safety measures.

3. Setting Test Parameters:

Based on test requirements, set suitable test current and duration by adjusting the output voltage and current of the power supply. At the same time, determine the sampling frequency and precision of the measuring equipment based on the circuit’s characteristics.

4. Conducting the Test:

After confirming that the test parameters are properly set, begin the high current injection test. During the test, monitor the current waveform and voltage response of the circuit being tested to assess its stability and reliability.

5. Analyzing the Results:

Analyze and evaluate the results of the test to determine the circuit’s performance and stability. If any abnormalities are found, further analysis can be conducted to pinpoint the cause, and appropriate repair and improvement measures can be taken.

In summary, high current injection testing is an effective automotive electronics EMC testing method that helps us evaluate a product’s resistance to interference and stability. By understanding the basic principles and operation steps of high current injection testing, we can better utilize this technology to ensure the safety of vehicles and the reliability of electronic products.

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