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Type B RCDs

M. Joshi
Increasingly, I am seeing a requirement for Type B RCDs in industrial applications, particularly where servo drives are used.


The preference is Type B RCBOs however, these are quite rare and not all manufacturers make them.


Aside from the high cost and short supply due to demand from EV and PV applications, how do others address this situation?


If the earthing is adequate, cables to the motors are run in trays and there is additional bonding to the motor housing, is there really a need for an RCD?
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    Large d.c. currents can do strange things to RCDs - often making less sensitive rather than defeating them completely - however even less sensitive is probably not what you want if it might affect a 30mA RCD used for additional protection.


    EVSE often use a combination of the much cheaper and readily available A-type RCD plus a device that'll trip if the d.c. component of the residual current exceeds 6mA - as A-type RCDs should tolerate 6mA d.c. and remain effective and the problem is disconnected if it exceeds that. That approach can also avoid the need for any upstream RCDs to be B-types too if there are no other loads that can cause a d.c. residual current.


       - Andy.
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  • 0
    Large d.c. currents can do strange things to RCDs - often making less sensitive rather than defeating them completely - however even less sensitive is probably not what you want if it might affect a 30mA RCD used for additional protection.


    EVSE often use a combination of the much cheaper and readily available A-type RCD plus a device that'll trip if the d.c. component of the residual current exceeds 6mA - as A-type RCDs should tolerate 6mA d.c. and remain effective and the problem is disconnected if it exceeds that. That approach can also avoid the need for any upstream RCDs to be B-types too if there are no other loads that can cause a d.c. residual current.


       - Andy.
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