What are the electromagnetic compatibility test standards for electric wheelchairs?

What are the electromagnetic compatibility test standards for electric wheelchairs?

1. Overview of electromagnetic compatibility test standards
1.1 Relationship between national standards and international standards
Electromagnetic compatibility (EMC) test standards are key specifications to ensure that electric wheelchairs operate normally in an electromagnetic environment and do not interfere with other equipment. Internationally, the IEC 60601 series of standards developed by the IEC (International Electrotechnical Commission) is the basic framework for electromagnetic compatibility of medical electrical equipment. Among them, IEC 60601-1-2 specifically targets electromagnetic compatibility requirements and specifies the test methods and limits for electromagnetic interference and immunity of medical equipment. my country’s national standard GB 9706.1 series corresponds to the IEC 60601 series. GB 9706.1-2020 integrates some clauses and clarifies that as mobile medical equipment, the electromagnetic compatibility test of electric wheelchairs must follow the GB 9706.1-2020 and GB 9706.102-2021 standards. GB 9706.102-2021 specifies the electromagnetic emission and immunity test items of electric wheelchairs in detail. For example, in the electromagnetic emission test, the conducted emission limit of the equipment is required to be 50 dBμV in the frequency band of 150 kHz to 30 MHz to ensure that it does not cause excessive interference to surrounding equipment; in the immunity test, for the radio frequency electromagnetic field radiation immunity, the equipment is required to withstand a field strength of 80 V/m in the frequency band of 80 MHz to 2.5 GHz to ensure normal operation in a complex electromagnetic environment. Based on the reference of international standards and combined with domestic actual conditions, our standards have refined the test conditions and equipment classification, making the standards more targeted and operational, and ensuring the safety and reliability of electric wheelchairs.

2. Emission test standards
2.1 Radiated emission limit
Radiated emission refers to the electromagnetic energy emitted by electric wheelchairs into the surrounding space during operation. According to GB 9706.102-2021 standard, the radiated emission test of electric wheelchairs mainly focuses on the frequency band of 30 MHz to 1 GHz. In this frequency band, the radiated emission limit of the equipment is 40 dBμV/m. This limit is set based on the need to protect the normal operation of other sensitive equipment in the medical environment. For example, in the intensive care unit (ICU) of a hospital, electric wheelchairs are used frequently, and there are also a large number of vital sign monitoring devices that are sensitive to electromagnetic interference in this area. By strictly controlling the radiated emission of electric wheelchairs, it is possible to effectively avoid their interference with these key medical devices and ensure the accuracy and reliability of medical equipment. In addition, the international standard IEC 60601-1-2 also stipulates the radiated emission limit, and its requirements are basically consistent with my country’s national standards, which shows that there are unified and strict requirements for the control of radiated emissions of electric wheelchairs worldwide to ensure the safety and stability of the medical environment.
2.2 Harmonic current emission requirements
Harmonic current emission is a nonlinear current generated by the power supply part of the electric wheelchair during operation, which will cause harmonic pollution to the power grid. According to the GB 9706.1-2020 standard, the harmonic current emission requirements of electric wheelchairs are mainly for the power input port. For electric wheelchairs with a rated current not exceeding 16 A, the harmonic current limit of the power input port shall comply with the provisions of the IEC 61000-3-2 standard. Specifically, within the 2nd to 39th harmonic range, the limit of each harmonic current is calculated based on the rated current and power factor of the device to ensure that the electric wheelchair does not cause excessive harmonic interference to the power grid during use. For example, when the rated current of the electric wheelchair is 10 A and the power factor is 0.8, its 2nd harmonic current limit is about 0.5 A. The implementation of this requirement is crucial to maintaining the power quality of the power grid, especially in places such as hospitals and nursing homes where electric wheelchairs are used more intensively. The stability and reliability of the power grid directly affect the normal operation of other medical equipment and facilities. By strictly controlling the harmonic current emission of electric wheelchairs, the harmonic content in the power grid can be effectively reduced, the power grid loss can be reduced, the power supply quality of the power grid can be improved, and a good power environment can be provided for the stable operation of electric wheelchairs and other medical equipment.

3. Immunity test standards
3.1 Electrostatic discharge immunity requirements
Electrostatic discharge is one of the sources of electromagnetic interference that electric wheelchairs may encounter in actual use. According to GB 9706.102-2021 standard, the electrostatic discharge immunity test of electric wheelchairs requires that the equipment can withstand electrostatic shocks of 8 kV contact discharge and 15 kV air discharge. This requirement is based on the situation that electric wheelchairs may come into contact with human bodies or objects in places such as hospitals and nursing homes, generating electrostatic discharge. For example, in a dry environment, the electrostatic voltage of the human body may be as high as several thousand volts. When the human body contacts the electric wheelchair, the static electricity will be instantly released to the device. Through strict electrostatic discharge immunity testing, it can be ensured that the electric wheelchair can still operate normally in this case, without problems such as misoperation, freezing or damage, to ensure the safety of users and the reliability of the equipment.
3.2 RF field radiation immunity requirements
RF field radiation immunity is one of the important indicators of electromagnetic compatibility of electric wheelchairs. According to GB 9706.102-2021 standard, electric wheelchairs need to be able to withstand 80 V/m of RF electromagnetic field radiation in the 80 MHz to 2.5 GHz frequency band. This frequency band covers common wireless communication bands, such as mobile phone signals, Wi-Fi signals, etc. In hospital environments, there are a large number of wireless communication devices, such as walkie-talkies and mobile nursing terminals used by medical staff. The RF electromagnetic fields generated by these devices may interfere with electric wheelchairs. By stipulating higher RF field radiation immunity requirements, it is possible to effectively avoid misoperation or performance degradation of electric wheelchairs in these complex electromagnetic environments, ensure their stable operation in medical environments, and provide users with safe and reliable travel tools.
3.3 Electrical fast transient pulse group immunity requirements
Electrical fast transient pulse groups are electromagnetic interference phenomena caused by electrical switch operations, etc. According to GB 9706.102-2021, the electrical fast transient pulse group immunity test of electric wheelchairs requires that the equipment can withstand the pulse voltage of the power port and signal port, with a pulse voltage amplitude of 2 kV and a pulse repetition frequency of 5 kHz to 100 kHz. In the actual use scenarios of electric wheelchairs, such as elevators and corridors in hospitals, frequent switching operations of electrical equipment may be encountered, which will generate fast transient pulse group interference. Through strict immunity testing, it can be ensured that the electric wheelchair can still operate normally under such interference, and there will be no problems such as motor stalling and controller failure, ensuring the travel safety of users and the stability of the equipment.
3.4 Surge immunity requirements
Surge is an electromagnetic interference phenomenon caused by lightning strikes, power grid switching, etc. According to GB 9706.102-2021, the surge immunity test of electric wheelchairs requires that the equipment can withstand the surge voltage of the power port, with a surge voltage amplitude of 2 kV and a waveform of 1.2/50 μs. In places such as hospitals, the power grid may be affected by external factors such as lightning strikes, generating surge voltage. As a medical device, the electric wheelchair needs to have a certain surge immunity to ensure that it can still operate normally in the case of a power grid surge without damage or performance degradation. By stipulating the surge immunity requirements, the reliability of the electric wheelchair in a complex power grid environment can be improved, and the safety of the user and the stability of the equipment can be guaranteed.
3.5 Voltage sag and short interruption immunity requirements
Voltage sag and short interruption are common electromagnetic interference phenomena in the power grid. According to the GB 9706.102-2021 standard, the voltage sag and short interruption immunity test of the electric wheelchair requires that the equipment can withstand a power supply voltage sag of 30% to 70% and a short interruption of 10 ms to 1 s. In places such as hospitals, the power grid may be affected by factors such as the startup and failure of other equipment, resulting in voltage sag and short interruption. As a mobile medical device, the electric wheelchair needs to be able to operate normally under these conditions without problems such as motor stalling and controller failure. By specifying the voltage sag and short-term interruption immunity requirements, the adaptability of electric wheelchairs in power grid fluctuation environments can be improved, ensuring the travel safety of users and the stability of equipment.

4. Special component test standards
4.1 On-board battery charger test requirements
The on-board battery charger is an important part of the electric wheelchair, and its electromagnetic compatibility has an important impact on the overall performance of the electric wheelchair. According to relevant standards, the electromagnetic compatibility test requirements of the on-board battery charger are as follows:
Emission test: In the frequency band of 150 kHz to 30 MHz, the conducted emission limit of the charger should be 46 dBμV to ensure that it will not cause excessive interference to surrounding equipment during the charging process. For example, in a hospital ward, the electromagnetic emission of the on-board charger of the electric wheelchair must be strictly controlled within the limit when charging to avoid interference with nearby medical equipment such as electrocardiogram monitors and affecting the accuracy of medical diagnosis.
Immunity test: The charger needs to be able to withstand 100 V/m radio frequency electromagnetic field radiation in the frequency band of 80 MHz to 2.5 GHz to ensure normal operation in a complex electromagnetic environment. In addition, the charger should also have good electrical fast transient pulse group immunity, and be able to withstand the pulse voltage of the power port and signal port, with a pulse voltage amplitude of 1 kV and a pulse repetition frequency of 5 kHz to 100 kHz. For example, in places such as hospital corridors, the on-board charger of an electric wheelchair may be interfered with by the radio frequency electromagnetic field generated by nearby wireless communication equipment and the fast transient pulse group interference generated by the switching operation of electrical equipment. Through strict immunity testing, it can be ensured that the charger can still work stably in this environment and provide reliable charging protection for electric wheelchairs.
4.2 Test requirements for off-board and portable battery chargers
Off-board and portable battery chargers are usually used to charge backup batteries for electric wheelchairs, and their electromagnetic compatibility is equally important. The relevant test requirements are as follows:
Emission test: The electromagnetic emission limits of off-board and portable battery chargers are basically the same as those of on-board battery chargers. In the frequency band of 150 kHz to 30 MHz, the conducted emission limit is 46 dBμV. This helps ensure that when these chargers are used in homes, nursing homes and other places, they will not cause significant electromagnetic interference to surrounding electronic devices such as televisions and stereos, ensuring that the user’s living environment is not affected.
Immunity test: The immunity requirements for off-board and portable battery chargers are also similar to those for on-board chargers. In the 80 MHz to 2.5 GHz frequency band, it is necessary to be able to withstand 100 V/m of radio frequency electromagnetic field radiation. At the same time, its electrical fast transient pulse group immunity requires a pulse voltage amplitude of 1 kV and a pulse repetition frequency of 5 kHz to 100 kHz. For example, in places such as nursing homes, when using off-board chargers to charge the spare battery of an electric wheelchair, it may be subject to electromagnetic interference generated by nearby wireless network equipment, etc. Through strict immunity testing, it can be ensured that the charger can still work normally under these interferences, provide a stable charging environment for the spare battery of the electric wheelchair, and ensure the normal use of the electric wheelchair.

5. Test methods and equipment
5.1 Test equipment requirements
In order to ensure the accuracy and reliability of the electromagnetic compatibility test of electric wheelchairs, the selection of test equipment is crucial. According to the GB 9706.102-2021 standard, the following are the requirements for the main test equipment:
Electromagnetic interference (EMI) test equipment:
Spectrum analyzer: used to measure the radiated emission and conducted emission of electric wheelchairs. The frequency range of the spectrum analyzer should cover 150 kHz to 30 MHz (conducted emission) and 30 MHz to 1 GHz (radiated emission) to meet the test frequency band specified in the standard. Its resolution bandwidth (RBW) should be adjusted according to the test frequency band, for example, it can be set to 100 kHz in the low frequency band and 1 MHz in the high frequency band to ensure the accuracy and repeatability of the test results.
Power amplifier and antenna: In the radiated emission test, appropriate power amplifiers and antennas are required to simulate the electromagnetic field in the actual use environment. The gain and radiation pattern of the antenna should meet the standard requirements to ensure the accurate propagation and reception of the test signal. For example, for radiated emission tests in the 30 MHz to 1 GHz frequency band, a logarithmic periodic antenna is usually used, and its gain should remain stable within this frequency band to ensure the accuracy of the test results.
Harmonic current analyzer: used to measure the harmonic current emission of the power input port of the electric wheelchair. The equipment should comply with the requirements of the IEC 61000-3-2 standard, be able to accurately measure the amplitude of the 2nd to 39th harmonic current, and make limit judgments based on the rated current and power factor of the equipment.
Electromagnetic immunity (EMS) test equipment:
Electrostatic discharge generator: used for electrostatic discharge immunity testing. The equipment should be able to generate electrostatic pulses of 8 kV for contact discharge and 15 kV for air discharge, and its pulse rise time and duration should comply with the standard to simulate the electrostatic discharge generated when the human body or object contacts the electric wheelchair in actual use.
RF electromagnetic field radiation generator: used to test the RF field radiation immunity of electric wheelchairs in the 80 MHz to 2.5 GHz frequency band. The equipment should have a stable RF signal output capability, be able to generate a field strength of 80 V/m, and its frequency range and field strength regulation accuracy should meet the standard requirements to ensure the accuracy and repeatability of the test results.
Electrical fast transient pulse group generator: used to test the electrical fast transient pulse group immunity of electric wheelchairs. The equipment should be able to generate a pulse group signal with a pulse voltage amplitude of 2 kV and a pulse repetition frequency of 5 kHz to 100 kHz. Its pulse rise time and duration should comply with the standard requirements to simulate electromagnetic interference caused by electrical switch operations, etc.
Surge generator: used to test the surge immunity of electric wheelchairs. The equipment should be able to generate a surge signal with a surge voltage amplitude of 2 kV and a waveform of 1.2/50 μs. Its surge rise time and duration should meet the standard requirements to simulate electromagnetic interference caused by lightning strikes, power grid switching, etc.
Voltage sag and short interruption generator: used to test the voltage sag and short interruption immunity of electric wheelchairs. The equipment should be able to generate a signal of a power supply voltage sag of 30% to 70% and a short interruption of 10 ms to 1 s. The amplitude and duration of the sag and interruption should comply with the standard to simulate the common electromagnetic interference phenomena in the power grid.
5.2 Test environment requirements
The setting of the test environment is equally important for the accuracy and repeatability of the electromagnetic compatibility test results. According to the GB 9706.102-2021 standard, the following are the main requirements for the test environment:
Electromagnetic shielding room: In order to reduce the impact of external electromagnetic interference on the test results, the test should be carried out in an electromagnetic shielding room. The shielding effectiveness of the shielding room should meet the standard requirements, for example, in the frequency band of 150 kHz to 1 GHz, the shielding effectiveness should not be less than 40 dB. The size of the shielding room should be large enough to accommodate the electric wheelchair under test and the test equipment, and the reasonable layout between the test equipment and the equipment under test should be guaranteed to avoid mutual interference.
Test site: In the shielding room, a special test site should be set up, including a test bench, a grounding system, etc. The test bench should have good electromagnetic compatibility to avoid electromagnetic interference itself. The grounding system should meet the standard requirements, and the grounding resistance should be less than 0.5 Ω to ensure good grounding of the test equipment and the equipment under test and reduce electromagnetic interference caused by poor grounding.
Environmental electromagnetic background noise: Before the test, the electromagnetic background noise of the test environment should be measured to ensure that it meets the standard requirements. For example, in the radiated emission test, the environmental electromagnetic background noise should be more than 10 dB lower than the emission limit of the equipment under test to avoid the impact of background noise on the test results. If the background noise is too high, appropriate measures should be taken, such as adjusting the parameters of the test equipment or changing the test environment to ensure the accuracy of the test results.
Temperature and humidity: The temperature and humidity of the test environment should meet the range specified in the standard, usually 20℃±5℃ and 45% to 75% relative humidity. Stable temperature and humidity conditions help to ensure the stable performance of the test equipment and the equipment under test, thereby ensuring the accuracy and repeatability of the test results.

6. Test process and sequence
6.1 Preparation before testing
Before conducting the electromagnetic compatibility test of the electric wheelchair, a series of preparations need to be completed to ensure the smooth progress of the test and the accuracy of the results.
Equipment inspection and calibration: All test equipment is inspected and calibrated to ensure that its performance meets the standard requirements. For example, the frequency range and resolution bandwidth of the spectrum analyzer should be accurate, and the discharge voltage and pulse parameters of the electrostatic discharge generator should meet the requirements. At the same time, check whether the key components of the electric wheelchair under test, such as the power supply, motor, and controller, are operating normally to ensure that they are in good working condition.
Test environment layout: Build the test environment in accordance with the standard requirements, including the setting of the electromagnetic shielding room, the layout of the test site, and the inspection of the grounding system. Ensure that the electromagnetic background noise of the test site meets the requirements to avoid external interference affecting the test results. For example, when conducting radiated emission tests, it should be ensured that the electromagnetic background noise of the test site is more than 10 dB lower than the emission limit of the device under test.
Sample preparation and identification: Identify the electric wheelchair under test and record its model, specifications, production date and other information. At the same time, check whether the battery power of the electric wheelchair is sufficient to ensure that the test results will not be affected by insufficient power during the test. For special components that need to be tested, such as on-board battery chargers, non-on-board and portable battery chargers, corresponding preparations should also be made.
6.2 Emission test process
The emission test focuses on the electromagnetic energy emitted by the electric wheelchair to the surrounding environment during operation, including radiated emission and conducted emission tests.
Radiated emission test:
Equipment layout: Place the electric wheelchair under test in the center of the test site to ensure that there is enough distance between it and the test antenna to meet the test conditions specified in the standard. For example, in the radiated emission test in the 30 MHz to 1 GHz frequency band, the distance between the device under test and the test antenna is usually required to be 3 m.
Test frequency band and limit setting: According to the GB 9706.102-2021 standard, the test frequency band is set to 30 MHz to 1 GHz, and the radiated emission limit is 40 dBμV/m. Use a spectrum analyzer and antenna to measure the radiated emission of the electric wheelchair, and record the emission intensity at different frequencies.
Test result determination: Compare the measurement results with the standard limits to determine whether the radiated emission of the electric wheelchair meets the requirements. If the emission intensity at a certain frequency point exceeds the limit, further analysis and improvement of the frequency point is required.
Conducted emission test:
Equipment connection: Connect the power cord of the electric wheelchair to be tested to the conducted emission test equipment to ensure that the connection is firm and reliable. At the same time, connect the input of the spectrum analyzer to the output of the test equipment to measure the conducted emission signal.
Test frequency band and limit setting: According to the standard requirements, set the test frequency band to 150 kHz to 30 MHz, and the conducted emission limit to 50 dBμV. Start the test equipment, measure the conducted emission of the electric wheelchair, and record the emission intensity at different frequencies.
Test result determination: Compare the measurement results with the standard limits to determine whether the conducted emission of the electric wheelchair meets the requirements. If there is an over-standard situation, it is necessary to analyze the cause and take corresponding measures to improve it, such as optimizing the power filter design.
6.3 Immunity test process
The immunity test mainly evaluates the performance of the electric wheelchair when it is subjected to external electromagnetic interference, including electrostatic discharge, radio frequency field radiation, electrical fast transient pulse group, surge and voltage sag and other immunity tests.
Electrostatic discharge immunity test:
Equipment layout: Place the electric wheelchair under test in a suitable position in the test site to ensure that there is enough operating space between it and the electrostatic discharge generator. At the same time, check whether the outer shell, armrests, seats and other parts of the electric wheelchair are prone to electrostatic discharge.
Test voltage and discharge mode setting: According to GB 9706.102-2021 standard, the contact discharge voltage is set to 8 kV and the air discharge voltage is set to 15 kV. Using the discharge method specified in the standard, perform multiple discharge tests on various easily contacted parts of the electric wheelchair to observe its reaction during the discharge process.
Test result determination: Record the performance of the electric wheelchair during the electrostatic discharge process, such as whether there is any misoperation, freeze, damage, etc. If the electric wheelchair can operate normally under the specified discharge voltage, it is considered that its electrostatic discharge immunity meets the requirements.
RF field radiation immunity test:
Equipment layout: Place the electric wheelchair under test in the center of the test site to ensure that there is enough distance between it and the RF electromagnetic field radiation generator to meet the test conditions specified in the standard. For example, in the RF field radiation immunity test in the 80 MHz to 2.5 GHz frequency band, the distance between the device under test and the radiation generator is usually required to be 1 m.
Test frequency band and field strength setting: According to the standard requirements, the test frequency band is set to 80 MHz to 2.5 GHz, and the RF electromagnetic field radiation field strength is 80 V/m. Start the radiation generator, perform RF field radiation test on the electric wheelchair, and observe its performance at different frequencies and field strengths.
Test result determination: Record the operating status of the electric wheelchair during the RF field radiation process, such as whether there is any misoperation, performance degradation, etc. If the electric wheelchair can operate normally under the specified field strength, it is considered that its RF field radiation immunity meets the requirements.
Electrical fast transient pulse group immunity test:
Equipment connection: Connect the power cord and signal line of the electric wheelchair under test to the electrical fast transient pulse group generator to ensure that the connection is firm and reliable. At the same time, check whether the key components of the electric wheelchair, such as the motor and controller, are susceptible to pulse group interference.
Test parameter setting: According to the standard requirements, set the pulse voltage amplitude to 2 kV and the pulse repetition frequency to 5 kHz to 100 kHz. Start the pulse group generator, perform an electrical fast transient pulse group immunity test on the electric wheelchair, and observe its response under pulse group interference.
Test result determination: Record the performance of the electric wheelchair during the pulse group interference process, such as whether the motor stops, the controller fails, etc. If the electric wheelchair can operate normally under the specified pulse group parameters, it is considered that its electrical fast transient pulse group immunity meets the requirements.
Surge immunity test:
Equipment connection: Connect the power cord of the electric wheelchair under test to the surge generator to ensure that the connection is firm and reliable. At the same time, check whether the power supply system of the electric wheelchair can withstand the impact of surge voltage.
Test parameter setting: According to the standard requirements, set the surge voltage amplitude to 2 kV and the waveform to 1.2/50 μs. Start the surge generator, perform a surge immunity test on the electric wheelchair, and observe its response under surge voltage.
Test result determination: record the performance of the electric wheelchair during the surge voltage process, such as whether it is damaged or performance degraded. If the electric wheelchair can operate normally under the specified surge voltage, it is considered that its surge immunity meets the requirements.
Voltage sag and short interruption immunity test:
Equipment connection: Connect the power cord of the electric wheelchair to the voltage sag and short interruption generator to ensure that the connection is firm and reliable. At the same time, check whether the power management system of the electric wheelchair can cope with voltage sag and short interruption.
Test parameter setting: According to the standard requirements, set the power supply voltage sag to 30% to 70% and the short interruption to 10 ms to 1 s. Start the generator, perform voltage sag and short interruption immunity test on the electric wheelchair, and observe its performance under different sag and interruption parameters.
Test result determination: record the operating status of the electric wheelchair during the voltage sag and short interruption process, such as whether the motor stops, the controller fails, etc. If the electric wheelchair can operate normally under the specified sag and interruption parameters, it is considered that its voltage sag and short interruption immunity meets the requirements.
6.4 Recording and analysis of test results
After completing each test, the test results need to be recorded and analyzed in detail in order to comprehensively evaluate the electromagnetic compatibility of the electric wheelchair.
Record test data: Record the parameters, measurement results, equipment status and other information of each test in detail in the test report. Including the measurement frequency band and emission intensity of radiated emission and conducted emission, the interference type, interference parameters, equipment response, etc. of the immunity test. For example, in the radiated emission test, record the emission intensity data at different frequencies; in the electrostatic discharge immunity test, record the discharge voltage, number of discharges and the operating status of the electric wheelchair.
Analyze test results: Analyze the recorded data to determine whether the electromagnetic compatibility of the electric wheelchair meets the standard requirements. For the situation of exceeding the standard, analyze the possible reasons, such as circuit design defects, insufficient shielding measures, etc. At the same time, evaluate the impact of the test results on the actual use of the electric wheelchair, such as whether it will affect the safety of the user and the reliability of the equipment.
Propose improvement suggestions: According to the test results and

7. Test result evaluation and report
7.1 Test result evaluation
After completing the electromagnetic compatibility test of the electric wheelchair, it is necessary to conduct a comprehensive evaluation of each test result to determine whether it meets the requirements of the relevant standards.
Emission test result evaluation:
Radiated emission: Compare the radiated emission test results with the 40 dBμV/m limit specified in the GB 9706.102-2021 standard. If the radiated emission intensity of the electric wheelchair is lower than the limit in the 30 MHz to 1 GHz frequency band, it is considered that its radiated emission meets the requirements. For example, the maximum radiated emission intensity of an electric wheelchair in the test frequency band is 35 dBμV/m, which is lower than the standard limit, indicating that it has little electromagnetic interference to the surrounding space during operation and will not have a significant impact on the normal operation of other sensitive equipment in the medical environment.
Conducted emission: For the conducted emission test results in the 150 kHz to 30 MHz frequency band, compare with the 50 dBμV limit. If the conducted emission of the electric wheelchair does not exceed the limit in this frequency band, it means that the electromagnetic interference of its power supply is well controlled and will not cause excessive interference to the power grid. For example, the maximum conducted emission of an electric wheelchair in this frequency band is 48 dBμV, which meets the standard requirements and helps maintain the power quality of the power grid.
Harmonic current emission: According to GB 9706.1-2020 The harmonic current of the power input port of the electric wheelchair is evaluated according to the IEC 61000-3-2 standard. Taking an electric wheelchair with a rated current of 10 A and a power factor of 0.8 as an example, its second harmonic current limit is about 0.5 A. If the test results show that its second harmonic current does not exceed the limit, and other harmonic currents also meet the standard requirements, it means that its harmonic pollution to the power grid is small, which is conducive to the stable operation of the power grid.

Evaluation of immunity test results:
Electrostatic discharge immunity: Check the operating status of the electric wheelchair under contact discharge 8 kV and air discharge 15 kV conditions. If the electric wheelchair can operate normally in multiple discharge tests without misoperation, freezing or damage, it is considered that its electrostatic discharge immunity meets the requirements of the GB 9706.102-2021 standard. For example, after multiple electrostatic discharge tests on different parts, an electric wheelchair can still travel, operate and control normally, indicating that it has good electrostatic discharge immunity and can effectively resist electrostatic interference generated by human or object contact in actual use.
Radiated radio frequency field immunity: In the frequency band of 80 MHz to 2.5 GHz, the electric wheelchair is tested with a radio frequency electromagnetic field radiation intensity of 80 V/m. If the electric wheelchair can operate normally in this frequency band and field strength without erroneous operation or performance degradation, it means that its radiated radio frequency field immunity meets the standard requirements. For example, in a hospital environment, even if an electric wheelchair is interfered by radio frequency electromagnetic fields generated by wireless communication devices such as intercoms and mobile nursing terminals used by medical staff, it can still operate stably to ensure normal use by users.
Immunity to electrical fast transient pulse groups: Apply electrical fast transient pulse group interference with a pulse voltage amplitude of 2 kV and a pulse repetition frequency of 5 kHz to 100 kHz to the power port and signal port, and observe the response of the electric wheelchair. If the motor of the electric wheelchair operates normally, the controller has no faults, and all functions are normal under the pulse group interference, it is considered that its electrical fast transient pulse group immunity meets the standard requirements. For example, in places where electrical equipment is frequently switched on and off, such as hospital elevators and corridors, electric wheelchairs can still travel normally, indicating that they have strong anti-pulse group interference capabilities.
Surge immunity: A surge voltage of 2 kV and a waveform of 1.2/50 μs is applied to the power port of the electric wheelchair to evaluate its immunity. If the electric wheelchair is not damaged and performs normally under the surge voltage impact, it meets the standard requirements. For example, when the power grid is affected by external factors such as lightning strikes and surge voltage is generated, the electric wheelchair can still work normally to ensure the safety of the user and the stability of the equipment.
Voltage sag and short-time interruption immunity: Test the operation of the electric wheelchair under the conditions of a power supply voltage sag of 30% to 70% and a short-time interruption of 10 ms to 1 s. If the electric wheelchair does not stop the motor and the controller does not fail under these power grid fluctuations, and all functions are normal, it is considered that its voltage sag and short-time interruption immunity meets the standard requirements. For example, in places such as hospitals, when the power grid is affected by factors such as the startup and failure of other equipment, the electric wheelchair can still operate stably, providing users with reliable travel guarantees.
Evaluation of special component test results:
On-board battery charger: For the emission test of the on-board battery charger, check whether its conducted emission in the 150 kHz to 30 MHz frequency band does not exceed the 46 dBμV limit. At the same time, in the 80 MHz to 2.5 GHz frequency band, evaluate whether it can withstand 100 V/m radio frequency electromagnetic field radiation and whether it has good electrical fast transient pulse group immunity (pulse voltage amplitude 1 kV, pulse repetition frequency 5 kHz to 100 kHz). If the charger meets the requirements in these test items, it means that it has good electromagnetic compatibility and can provide reliable charging guarantee for electric wheelchairs in places such as hospital wards, and will not interfere with surrounding medical equipment.
Off-board and portable battery chargers: Their emission test and immunity test requirements are basically the same as those of on-board battery chargers. In the frequency band of 150 kHz to 30 MHz, the conducted emission limit is 46 dBμV; in the frequency band of 80 MHz to 2.5 GHz, it must be able to withstand 100 V/m of radio frequency electromagnetic field radiation, and the electrical fast transient pulse group immunity requires a pulse voltage amplitude of 1 kV and a pulse repetition frequency of 5 kHz to 100 kHz. If the test results of non-vehicle and portable battery chargers meet these requirements, it means that when used in homes, nursing homes and other places, it will not cause obvious electromagnetic interference to surrounding electronic equipment, and it can also work stably in complex electromagnetic environments, providing a good charging environment for the backup battery of the electric wheelchair.