How is residual current generated during electric vehicle charging?
During the charging process of an electric vehicle, the On-Board Charging (OBC) system plays a crucial role in converting the alternating current (AC) from the mains to direct current (DC) to charge the vehicle's battery. However, there is a potential risk of current leakage or ground faults, which can have serious consequences such as electrocution, electrical fires, or damage to vehicle components. Therefore, it is imperative to detect and protect against these residual currents.
The following diagram illustrates a typical electrical configuration of an On-Board Charging (OBC) system, comprising an input EMI filter, an AC/DC rectifier, a PFC circuit, a DC/DC converter, and an output EMI filter. Over time, and due to vibrations and the aging effects inherent in electric vehicle use, an OBC insulation failure may occur.
Fig. 1 - Diagram of the On-Board Charging System (OBC)
Depending on the location of the fault, different types of residual currents are generated in the EV charging system:
① A ground fault at the AC input of the grid would result in a sinusoidal AC residual current at the grid frequency.
② A ground fault in the AC/DC rectifier section of the OBC will result in a pulsating DC residual current.
③ A ground fault in the DC/DC conversion stage of the OBC will produce a uniform DC residual current.
Therefore, it is essential to be able to detect sinusoidal AC residual current, pulsating DC residual current, and uniform DC residual current throughout the EV charging system to protect electrical installations and prevent the risk of electric shock to humans. With advancements in battery charging technology, relevant IEC standards have established specific requirements for residual current devices (RCDs) to ensure adequate protection during electric vehicle charging.
What type of residual current device (RCD) should be used for protection?
Selecting the appropriate RCD depends on the specific requirements. An RCD is designed to detect earth fault currents and interrupt the power supply in the event of an earth leakage current. Its primary function is to protect electrical circuits and the human body from electric shock and fire.
There are several types of RCDs, each capable of detecting different types of residual currents. According to the international standard IEC 60755, four types of RCDs are defined for AC applications: Type AC, Type A, Type F, and Type B.
AC-type RCDs are designed only to detect sinusoidal AC residual currents, restricting their use to basic devices that do not generate uniform DC residual currents. These RCDs are commonly used in general applications such as household appliances, incandescent lamps, and water heaters.
Type A RCDs are capable of detecting the same sinusoidal residual currents as type AC RCDs. However, they can also detect pulsating DC residual current, and pulsating DC residual current superimposed on uniform DC residual current up to 6mA, making them suitable for applications in residential and commercial buildings, such as induction cooktops, microwave ovens, dishwashers, and computers of all types.
Type F RCDs are used when the application may generate a composite residual current. They can withstand uniform continuous residual currents of up to 10 mA superimposed on the residual current. Furthermore, a Type F RCD can also detect all residual currents detected by a Type A RCD. These devices are commonly used for protection in applications such as single-phase heat pumps, variable frequency air conditioners, pool pumps, and washing machines.
The international standard IEC 61581-1 offers two alternatives for protection against uniform residual currents in charging stations: a type B RCD can be used, or a type A + DC 6mA RCD together with a suitable device that disconnects the power supply if the leakage current exceeds 6mA.
Residual Current Device Requirements for Electric Vehicle Chargers
For AC and DC charging stations, different EV charging modes have specific requirements for residual current devices (RCDs). The specific requirements according to industry standards for electric vehicle chargers are described below:
For charging mode 2 (IC-CPD), IEC 62752 specifies that in-cable control and protection devices (IC-CPDs) must ensure the activation of residual sinusoidal AC, pulsating residual DC, and uniform residual DC exceeding 6 mA, whether applied suddenly or gradually increasing. Similarly, for charging mode 3 (RDC-DD), IEC 62955 defines residual DC detection devices (RDC-DDs) as being designed to suppress or initiate the suppression of the supply to the EV in cases where a uniform residual DC of 6 mA or higher is detected. Plug-in DC charging stations for electric vehicles in mode 4 must be compatible with Type A RCDs, be equipped with an RCD, and may also have an overcurrent protection device.
Type B RCDs are typically more expensive, so many EV charging station manufacturers opt for a Type A + DC 6mA RCD solution to meet the standard requirements.
Why choose the Mornsun Type A+ DC 6mA Residual Current Detection Module (Electronics OLFER: Authorized Distributor)?
As a leading and innovative power supply manufacturer, Mornsun (distributed in Spain and Portugal by Electronics OLFER) is dedicated to providing comprehensive power supply solutions for various sectors, including the TLB6-A1 series of Type A+ DC 6mA residual current detection modules for electric vehicle charging. This solution can be flexibly adapted to different application scenarios, improving system stability and safety while reducing costs. Let's now explore the advantages and highlights of the Mornsun TLB6-A1 series.
Wide range of applications:
The TLB6-A1 series offers a compact size and multiple enclosure designs, allowing it to meet different board design and installation requirements for both single-phase and three-phase inputs. This flexibility enables it to adapt to various application scenarios and provide comprehensive protection.
High performance.
The Type A + DC 6mA residual current detection solution for electric vehicle charging provides comprehensive and effective protection against various types of leakage currents, outperforming conventional Type A and Type AC solutions. Compared to other modules, the TLB6-A1 series RCD module stands out due to its integrated circuit (IC), protected by its own intellectual property rights, which offers the following advantages:
1) Comprehensive protection functions including overvoltage protection, inrush current protection, and magnetic saturation protection.
2) Excellent trip threshold performance, temporal stability, and minimal batch-to-batch differences.
3) Innovative dual-threshold detection algorithm and current waveform identification for accurate and rapid detection of residual currents.
4) EMC protection designed to prevent system failure when a leakage fault occurs, or unnecessary activation when no fault is present.
5) Calibration function to eliminate the influence of small leakage currents generated by environmental factors or system parasitic currents on the actual leakage currents.
High safety
The Mornsun TLB6-A1 series Type A+ DC 6mA residual current detection module complies with IEC61851, IEC 62752 and IEC 62955 standards, enabling it to easily detect DC, AC and various pulsating residual currents with high response speed and excellent accuracy.
With its self-contained magnetic recovery technology, the TLB6-A1 series boasts an overcurrent capacity of up to 3,000A. It operates reliably in harsh environments thanks to its high resistance to electromagnetic interference and comprehensive protection features. These modules are widely used for current detection in sectors such as electric vehicle charging, low-voltage equipment, photovoltaic systems, and more, thanks to their advantageous characteristics and wide operating temperature range (-40°C to +85°C).
Profitability
With in-house production of key components, a strong R&D team, a stable supply chain, sufficient production capacity and an advanced production management system, Mornsun ensures consistently high reliability in series production, while guaranteeing fast delivery and cost savings for customers.
Conclusion:
With the growing demand for electric vehicle charging stations, manufacturers face a real challenge in differentiating themselves. However, Mornsun's optimal residual current detection modules, distributed in Spain and Portugal by Electrónica OLFER, can help you meet current detection limit requirements and improve the competitiveness of your electric vehicle charging system. They provide comprehensive protection while reducing design and maintenance costs. If you need a specific RCD solution for your projects, Mornsun is undoubtedly an excellent choice. We also offer test equipment or simple test boards for functional verification. In addition, we provide other intelligent control modules, such as high-performance, small-sized current transducers, contactor control modules, and DC contactors to meet diverse current detection needs.
Are you ready to choose a residual current detection module that suits your applications and aligns with your business objectives? Don't hesitate to contact us at www.olfer.com; we guarantee we have the optimal solution tailored to your needs!
