A detailed explanation of IEC 62955: Why detecting 6mA DC leakage current is critical for EV chargers.

As electric vehicles (EVs) gain popularity in Europe and India, charger manufacturers are facing a growing challenge that is often overlooked during product development: residual current protection (RCP).

While charging speeds, communication protocols, and ease of use receive significant attention, leakage current protection remains one of the most important safety requirements for electric vehicle charging systems.

Even one undetected DC short circuit current can damage protective devices, increase the risk of electric shock and ultimately prevent compliance with international standards.

Therefore, standards such as IEC 62955 and IEC 62752 now require a dedicated residual current monitoring function in many electric vehicle charging systems.

Understanding Leakage Current in Electric Vehicle Charging Systems.

Unlike conventional electrical devices, electric vehicle chargers contain the following power electronic components:

• AC/DC converter
• rectifier
• On-board charging circuit
• power factor correction module

In the event of failure, these components can generate different types of short-circuit currents:

• AC short-circuit current
• Leakage currents are a common phenomenon in electrical installations, typically occurring in conventional AC circuits.
• pulsating continuous residual current
• It is generated using rectifier circuits and electronic switching devices.
• Smoothing of residual DC current

This is the most severe failure scenario, as it may exceed the capabilities of normal protective devices.

Once the smoothed DC leakage current exceeds 6mA, a standard type A residual current circuit breaker may no longer provide reliable protection.

For this reason, dedicated RDC-PD solutions are becoming increasingly important.

Reasons for introducing the IEC 62955 standard

The IEC 62955 standard is specifically designed for residual current detection devices (RDC-DD/RDC-PD) used in electric vehicle charging systems.

The standard is aimed at achieving one main goal:

These currents are detected before dangerous residual direct currents disrupt the operation of protective devices.

For charger manufacturers targeting the European market, compliance with the IEC 62955 standard is often a prerequisite for certification and market access.

With the growing adoption of international safety standards, charging infrastructure projects in India are also increasingly adopting the same approach.

Cost issues with Type B residual current circuit breakers.

Historically, residual current devices (RCDs) of type B were used to detect residual AC and DC currents.

However, many charger manufacturers have encountered a number of practical problems:

• Higher system costs
• More space for installation
• Increase in the cost of materials
• Compact chargers offer limited design options.

These factors become increasingly important as forklift production volumes increase.

This has prompted the industry to adopt RDC-PD-based architecture to achieve the required level of security while reducing overall system costs.

 

How RDC-PD technology works?

The RDC-PD system continuously monitors the total residual current flowing through the charging system.

If the leakage current exceeds a set threshold level, the monitoring unit immediately sends an activation signal to the charge controller.

The controller can then:

• Continuous load
• Open the door
• Notify users
• Log error events

This approach allows charger manufacturers to implement protection measures that comply with the standards without having to rely entirely on expensive Type B RCD solutions.

Design issues of charging devices for electric vehicles.

When selecting a residual current monitoring solution, engineers need to consider more than just the tripping current value.

Key factors include:

• Detection accuracy
• The device must be able to reliably detect residual AC and DC currents under various environmental conditions.
• Self-testing capability
• Periodic self-tests help ensure the proper operation of monitoring circuits throughout the product life cycle.

Preparing for regulatory compliance

Compliance with IEC 62955 can significantly simplify the certification process.

 

Environmental compatibility

Charging stations are often exposed to harsh environmental conditions, including:

• External structures
• Areas with high humidity
• high temperature
• industrial charging stations
• Long-term stability is vital.

 

For example: integration of RDC-PD into modern electric vehicle chargers.

In practice, this usually includes the following:

• Residual current monitoring unit
• Control microcontroller
• Power contactor
• Type A residual current circuit breaker
• load controller

The monitoring unit continuously monitors the leakage current and transmits fault information to the control electronics.

Modern RDC-PD modules may also include the following:

• Calibration function
• Digital output signal
• Self-diagnosis
• Compact PCB integration

These features help reduce development complexity while improving the overall security of the system.

HYCA-07-PD: Practical RDC-PD solution for charging EV

The HYCA-07-PD residual current monitoring unit is an example of this type of application.

This device is specially designed for charging electric vehicles and supports the following functions:

• Detection of AC and DC short-circuit currents
• Application requirements according to IEC 62955
• Application requirements according to IEC 62752
• Built-in self-diagnosis function
• Assembling a printed circuit board
• 5V Power Supply Architecture
• Integration of compact systems
• Wide range of operating temperatures

Application of protective equipment for electric vehicle charging stations

This module is capable of detecting residual currents required for RDC-PD operation and is suitable for charging systems in the private and commercial sectors.

 

The Future of Electric Vehicle Charging Safety

As electric vehicle charging infrastructure expands in Europe and India, safety standards will also evolve.

Manufacturers that implement regulatory-compliant residual current monitoring early in product development will benefit from:

• Accelerated authentication
• Reducing redesign costs
• Improving system reliability
• Improving user security
• More efficient access to regulated markets.

Residual current monitoring is no longer an optional feature; it has become a fundamental element of modern EV charging architecture.

Compay：HEYI Electrical Co., Ltd.
Brand: HEYI/ASCT
Contact: Bethy
E-mail: heyi@heyiele.com             
Tel: 86-13968747975

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