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Reg 419.2 Applicable to VSD driven motor?

Steven WALKER

Good afternoon,

When using cable design software such as ElectricalOM, there is a check box within the "Earthing" tab / adiabatic check of CPC. It states Provision of  regs 419.2 & 419.3 are applicable. (BS7671)

If checked it will remove the warning regarding the earth fault / disconnection time (should a warning exist with the modelled install)

Can someone confirm with a degree of certainty that the checkbox would reg 419.2 be applicable to a motor supplied from a VSD drive? 

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  • 0

    Probably correct ... although there might be some layouts where the wiring between the VSD and motor would fall back into BS 7671's scope.

    If it did, then data from the VSD manufacturer is probably the way to go. I many cases I would have thought that the impedances involved would mean that the to produce a voltage difference exceeding 50V into a short(ish) circuit, the VSD would have to produce such a large current that either it would shut down promptly to protect itself or it would go phut and let all the magic smoke escape, so achieving ADS in a rather one-off if roundabout manner.

    Or if there is any doubt, apply supplementary bonding (419.3 option).

       - Andy.

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  • 0

    Probably correct ... although there might be some layouts where the wiring between the VSD and motor would fall back into BS 7671's scope.

    If it did, then data from the VSD manufacturer is probably the way to go. I many cases I would have thought that the impedances involved would mean that the to produce a voltage difference exceeding 50V into a short(ish) circuit, the VSD would have to produce such a large current that either it would shut down promptly to protect itself or it would go phut and let all the magic smoke escape, so achieving ADS in a rather one-off if roundabout manner.

    Or if there is any doubt, apply supplementary bonding (419.3 option).

       - Andy.

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  • 0 in reply to AJJewsbury
    AJJewsbury said:
    Or if there is any doubt, apply supplementary bonding (419.3 option).

    419.3 is not an option because 419.3 starts by stating "except where reg 419.2 applies" 

    I thought  reg 419.2  had been written with VSD drives in mind (albeit very vaguely) as they have in built fault protection, which by my limited knowledge the electronics would disconnect the output within with the required disconnection time. 

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