ZS for an motor run off an inverter

Mr Jack

The inverter does provide fault protection as I explained above. I also do not understand Grahams comment on shock protection, as bonding and Earthing are still required in the usual way. It is true that there is no shock protection for contact with an inverter output and Earth at the same time, but this scenario should be impossible with correct installation. For RCD lovers, there is the possibility that one might work in the inverter output, but is so far outside the design specification that what happened on fault would be unknown. Nuisance tripping would be a major problem too, as the output waveforms do not necessaraly sum to zero at all times, and the fast edges at several kHz would have unknown effects. The average RCD tester would not work because the waveform is at zero for a proportion of the time in normal operation, and this would probably trigger the timing circuit as a trip.


It is also debatatable as to whether inverter wiring is covered by BS7671, as it is really an appliance, connected to the fixed wiring system. However, I am going to leave that problem alone!

Mr Jack

The inverter does provide fault protection as I explained above. I also do not understand Grahams comment on shock protection, as bonding and Earthing are still required in the usual way. It is true that there is no shock protection for contact with an inverter output and Earth at the same time, but this scenario should be impossible with correct installation. For RCD lovers, there is the possibility that one might work in the inverter output, but is so far outside the design specification that what happened on fault would be unknown. Nuisance tripping would be a major problem too, as the output waveforms do not necessaraly sum to zero at all times, and the fast edges at several kHz would have unknown effects. The average RCD tester would not work because the waveform is at zero for a proportion of the time in normal operation, and this would probably trigger the timing circuit as a trip.


It is also debatatable as to whether inverter wiring is covered by BS7671, as it is really an appliance, connected to the fixed wiring system. However, I am going to leave that problem alone!