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RCD types

Farmboy
Regarding RCD types, AC, A, F, etc. Do these classification/types apply only to RCD's installed in CU's/DB's, or to RCD's incorporated in RCD sockets and fused connection units as well? A manufacturer is getting back to me about their products later in the week, and I'd like to have something to compare their answer to.


F
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    Changing the design of an AC to an A is a fairly small change, in many cases no design change at all.

    To make a B type is a more significant step, involving a new DC sensing part, either a Hall effect device or in the case of ABB a flux gate, where a magnetic  core is driven to saturation alternately in both polarisations by an audio frequency AC, and the DC field is deduced from the asymmetry of the current waveform relative to the voltage.

    If I was a maker and I had produced a device, be it a DIN rail RCD that meets an IEC spec or not,  that met a harder spec than the previous model, and covered a wider range of fault cases, I'd be declaring it, even if not using the nomenclature AC A or B; which given we already have B and C curves for MCBs is a pretty stupid classification anyway ( but that is committees that don't talk to each other.)


    edit - an  example of a flux gate  DC current sensor as a hobby project,  albeit a rather deaf one to give a feel for the complexity.
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  • 0
    Changing the design of an AC to an A is a fairly small change, in many cases no design change at all.

    To make a B type is a more significant step, involving a new DC sensing part, either a Hall effect device or in the case of ABB a flux gate, where a magnetic  core is driven to saturation alternately in both polarisations by an audio frequency AC, and the DC field is deduced from the asymmetry of the current waveform relative to the voltage.

    If I was a maker and I had produced a device, be it a DIN rail RCD that meets an IEC spec or not,  that met a harder spec than the previous model, and covered a wider range of fault cases, I'd be declaring it, even if not using the nomenclature AC A or B; which given we already have B and C curves for MCBs is a pretty stupid classification anyway ( but that is committees that don't talk to each other.)


    edit - an  example of a flux gate  DC current sensor as a hobby project,  albeit a rather deaf one to give a feel for the complexity.
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