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Swimming pool 3 phase motor trips occasionally on earth leakage RCD

CliveS
We have a new 4 kW 3 phase pump motor at the local pool which has a new variable speed drive unit attached and occasionally it trips out on the RCD which I assume is 30mAmp .  The connections are star inside the motor but not earthed which should have stopped it tripping.

We are not sure what to do, we could run the motor flat out and delta connect the windings possibly or some suggest disconnecting the RCD as the circuit is completely separate from normal wiring.  Would this option contravene any of our regs?
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    the losses can be reduced by being less stingy with the copper and the iron,  but motor makes do not want to re-tool immediately . The better made motor cost is higher, but the cost to run over all but the shortest  lifetime is not. It might have been more effective to ditch the vsd requirement and just insist  on lower losses.

    However there is an additional complication that motor frames are only made in a limited number of sizes so the chances are that your motor has to be  oversized for the pump, perhaps only by 10% or so, but still oversized. in such a case it can safely be run a little lighter than flat out and still pump the same.

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    the losses can be reduced by being less stingy with the copper and the iron,  but motor makes do not want to re-tool immediately . The better made motor cost is higher, but the cost to run over all but the shortest  lifetime is not. It might have been more effective to ditch the vsd requirement and just insist  on lower losses.

    However there is an additional complication that motor frames are only made in a limited number of sizes so the chances are that your motor has to be  oversized for the pump, perhaps only by 10% or so, but still oversized. in such a case it can safely be run a little lighter than flat out and still pump the same.

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