[Considerations on EMC Issues of Leakage Current Detection Elements in Type B IC-CPD] With the increasing popularity of electric vehicles, the safety regulations for electric vehicle charging are becoming more and more stringent. As we all know, there are four charging modes for electric vehicles. Mode 1 has been explicitly prohibited because it cannot provide effective protection. Mode 2 is based on Mode 1, with a protection box (IC-CPD) installed on the charging cable to display and protect against fault current. Mode 3 is charging via AC charging piles. Mode 4 is charging via DC charging piles.
Taking Mode 2 as an example, to ensure safety during the charging process, many OEMs, especially foreign and domestic joint venture OEMs, require protection against DC leakage current of 6mA, according to standard IEC62752-2016. Traditional leakage current detection technology cannot detect DC 6mA. MAGTRON's RCMU series leakage current sensors can meet this requirement and can detect various other complex waveform leakage currents (Type B leakage current).
Figure 1. Four charging modes for electric vehicles
Meanwhile, the cable control protector (IC-CPD) for electric vehicle mode 2 charging is an AC slow charging device that can be used during off-peak electricity pricing periods. The IC-CPD is mainly used in garages where it is not suitable to install charging piles and as a backup charging method. In principle, every electric passenger vehicle needs to be equipped with one. Unlike charging piles, its usage scenarios are not fixed. It may be in a garage or anywhere with a socket. Therefore, it faces a more complex electromagnetic environment and needs to ensure good electromagnetic compatibility (EMC).
As the most important key component in IC-CPD for realizing leakage protection, the leakage current sensor plays a vital role in protecting human safety during charging, and its EMC issues need to be carefully considered.
According to the EMC requirements of IEC 62752-2016, the EMC testing standard is based on IEC 61543 "Residual current-operated protective device (RCDs) for household and similar use - Electromagnetic compatibility". This refers to the electromagnetic compatibility standard for residual current protection devices for household and similar uses.
Figure 2. EMC test requirements in IEC 62752-2016
The standard electromagnetic environment specified in IEC 61543 refers to the environmental conditions occurring in equipment connected to a low-voltage public power grid or similar lines. It mainly includes low-frequency electromagnetic phenomena, high-frequency electromagnetic phenomena, and electrostatic discharge (ESD). Low-frequency electromagnetic phenomena include harmonics, interharmonic waves, signal voltage, voltage amplitude variations, voltage imbalances, power supply frequency variations, and radiated magnetic fields from the DC component of induced low-frequency voltage AC power grids. High-frequency electromagnetic phenomena include unidirectional transient conduction (pulse groups) at the nanosecond (ns) level, unidirectional transient conduction at the millisecond (ms) level, and high-frequency radiation of transient oscillating currents at the microsecond (µs) level. ESD refers to materials that may exhibit ESD under low humidity conditions.
IEC 61543's electromagnetic compatibility testing for residual current devices (RCDs) mainly includes two aspects: electromagnetic emission (EMI) and electromagnetic immunity (EMS) testing. IC-CPDs, as passive protection components, generally do not have internal high-frequency oscillators and do not emit external radiation, so EMI testing is generally not performed. Therefore, EMS issues need to be considered. As we know, sensors are low-level electronic devices that process relatively weak signals. The power supply line of the leakage current sensor passes through the sensor. Although there is sufficient electrical isolation, due to its small size and the close proximity of the PCB and power supply line, interference can easily couple into the type B leakage current sensor . In complex electromagnetic environments, even extremely small external electromagnetic interference can cause significant errors in the output, or even incorrect results.
The radio frequency electromagnetic field immunity test in IC-CPDEMC testing is a particularly troublesome issue in the product certification testing process. While engineers are constantly optimizing the PCB design, they also need to select components with better immunity, which places higher demands on the electromagnetic field immunity of leakage current sensors.
The corresponding national standard IDT version of IEC 61543 is GB 18499 "Electromagnetic Compatibility of Residual Current Operated Protective Devices (RCDs) for Household and Similar Purposes", which is adopted equivalently. The following figure shows the test requirements for radiated electromagnetic fields in GB 18499.
Figure 3 shows the test requirements for radiated electromagnetic fields in GB18499.
Figure 4 shows section 5.1 of GB/T17626.3-2003 .
GB/ T17626.3-2003, "Electromagnetic Compatibility Testing and Measurement Techniques - Radio Frequency Electromagnetic Field Radiation Immunity Test," specifies three test levels corresponding to field strengths of 1V/m, 3V/m, and 10V/m, respectively (GB/T17626-2016 adds a fourth level, corresponding to a field strength of 30V/m), covering a frequency range of 80MHz to 1GHz. Residual current operated protective devices correspond to level 2, with a test field strength of 3V/m.
Figure 5 Electromagnetic radiation test of RCMU series leakage current sensor
Through testing of MAGTRON's RCMU series leakage current sensor, its actual electromagnetic radiation immunity remains stable in a vertical field strength of 10V/m and a radiation frequency of 80M~1GHz, without affecting its detection.
IEC 62752 is actually a basic standard for Type B IC-CPDs. It considers IC-CPDs as components outside the automotive industry, so its EMC requirements are relatively low. Generally, 3V/m field strength is considered a requirement for commercial-grade products, 10V/m for industrial-grade products, and automotive-grade requirements are above 100V/m. Different OEMs have different requirements, generally ranging from 100V/m to 140V/m. In our collaborations with OEMs, we've found that since IC-CPDs are essential components in electric passenger vehicles, the responsibility lies with the OEM. Therefore, even though IC-CPDs are not part of the automotive system, OEMs still apply automotive-grade requirements. MAGTRON's RCMU leakage current sensor passed the 140V/m test in an OEM's IC-CPD whole-unit test!
Magtron's SoC chip solution based on iFluxgate technology provides safe and reliable components for Type B leakage protection in electric vehicle charging.
References
[1]IEC62752-2016In-cablecontrolandprotectiondeviceformode2chargingofelectricroadvehicles(IC-CPD)
[2]IEC61543-1995Residualcurrent-operatedprotectivedevice(RCDs)forhouseholdandsimilaruse-Electromagneticcompatibility
[3] GB/ T17626.3-2003 Electromagnetic compatibility testing and measurement techniques: Radio frequency electromagnetic field radiation immunity test
[4] GB18499 Electromagnetic compatibility of residual current operated protective devices (RCDs) for household and similar purposes
