How to select 6 mA DC RCM for mode-3 EV charging points
6 mA DC RCM – officially named as residual direct current detection device (RDC-MD) according to IEC 62955 standard – has been widely used in mode-3 EV charging point. This article introduces how to select 6 mA DC RCM for mode-3 EV charging points.
6mA DC RCM – officially  named as residual direct current monitoring device (RDC-MD) according to IEC 62955 standard – has been widely used in mode-3 EV charging point since the update of IEC 61851-1 standard in 2017. 

There are mainly three types of 6 mA DC RCM in the market.

  1. Independent DC RCM supplied by 230V power source : The DC RCM in the left part of the following diagram draws power from the 230/380V power system. It is able to directly switch off the control devices at the 230V/380V main circuits in the occur of DC residual current.
  2. Independent DC RCM supplied by 12V power source: The DC RCM in the middle part of the following diagram is supplied by 12V power source at a mode-3 EV charging controller. An external pull-up resistor is usually needed at Trip/Fault pin of a 12V DCM.
  3. Built-in 6 mA DC RCM at mode-3 EV charging controller: A DC residual current sensor supplied by 5V power is integrated into a charging controller, which helps the entire charging controller meet the IEC 62955 standard about RDC-MD. 
Three types of 6 mA DC RCM in the market
Diagram A: three types of 6 mA DC RCM in the market

As China’s leading technology provider of residual current protection, Bituo has noticed the third type of 6 mA DC RCM is favored by most of professional EV charging point manufacturers in IEC market (Europe and most of countries in Asia, Africa and Latin America). In other words, it is a main-stream approach to monitor DC residual current via a built-in 6 mA DC RCM at a mode-3 EV charging controller.  

Electronic engineers told us that a built-in 6 mA DC RCM has advantages of cost saving and design flexibility. E.g. the cost of 12V-to-5V and 230V-to-5V power supply modules powering the fluxgate circuit that detects DC residual current can be saved at a built-in 6 mA DC RCM in comparison with the 1st and 2nd type of 6 mA DC RCM respectively. Moreover, a built-in 6 mA DC RCM at mode-3 EV charging controller facilitates electronic engineers to add anti-noise program in the charging controller MCU, so as to prevent the happening of “false” tripping. 

In order to make it easy for electronic engineers to design their own built-in 6 mA DC RCM at mode-3 EV charging controller, Bituo offers BRCS01/02 residual current sensors with a wide range of installation variants- cable-integration variant with Molex connector , cable-integration variant with XHB connector, standing-on-PCBA variant, laying-on-PCBA variant with copper conductor passing through the ring, as well as laying-on-PCBA variant with cables passing through the ring. 

BRCS01/02 IEC 62955 residual current sensors with a wide range of installation variants
Diagram B: BRCS01/02 IEC62955 residual current sensors with a wide range of installation variants

The selection of BRCS01/02 sensor installation variants are firstly influenced by EV charger enclosure design. E.g. our BRCS02 sensor that measures both charging current and residual current is very popular for compact 7kW home charging points sold in the UK and China market. The double-floor design of CT and ZCT at BRCS02 saves space on the charging controller PCBA needed for CT measuring charging current. For EV charging points aiming to have large-volume sales, we recommend the laying-on-PCBA variant because of its saving of wiring time at manufacturing variant. Moreover, cable-integration variants are very popular for public charging points with modular design, so as to replace the failed sensor with a new one quickly during on-site maintenance. 


Overall, the question of “how to select 6 mA DC RCM for mode-3 EV charging points” can be answered with a two-step suggestion. The first step is to make your decision of selecting built-in 6 mA DC RCM at mode-3 EV charging controller. The second step is to select the right DC residual current sensor installation variants fitting best for your overall EV charging point design. Afterwards, it might take some efforts to do the sensor integration, but it has been proved to be worth doing it by many professional EV charging point manufacturers worldwide. If you need any support about the topic of built-in 6 mA DC RCM at mode-3 EV charging points, please don’t hesitate to contact us via sending Email to info@bituo-technik.com .

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