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Electrical noise created by 3ph machine

Steve Phillips

Hello all

Life long sparky... semi-retired now, but working at a local workshop

The company had a local (rather shoddy) electrical company come in and re-supply a 3ph, 35A per phase painting/spray machine.    It was fed before and created flickering in the office fluorescent lights.

But, it still does it.  The fluorescent lights in the offices on the mezzanine nearby flicker when the machine pulls a high load.

It's fed from a sub DB that has a 125A, 25mm 3ph SWA supply (This run is considerable from the incomer - probably somewhere like 70M+.   

Machine MCB is 32A

They used 6mm 5 core SY cable (I would have gone 10mm) over a 25M run.  But they laid it on top of (not in) a 4" galv trunking with T&E inside.  Entirely possible the lighting feeds run within this trunking.

I may unstitch the cable and move it away from the trunking, but I am not entirely convinced that is the issue.

Any ideas on what to try?  

Personally, I would rewire the machine directly back to the incoming mains cupboard, but that is no easy task.

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  • 0

    The fluorescent lights in the offices on the mezzanine nearby flicker when the machine pulls a high load.

    Before un-routeing a load  of cable, if you can, see how much the voltage on the wiring to the lights is wobbling about - it may be good old fashioned voltage drop, and 'conducted emissions' rather than a radiated EM .
    If the motor draws 30A phase when up to speed it may be trying, and failing, to get a few times that during start up and changes of speed . If so, Mr Ohms law may be enough to explain a lot of the rest. You will need a voltage logger or scope (can be hired) or at least a meter with a very fast response or max/min hold.

    Is it easier to lay in a new main for the lights and delicates , rather than the motor ?
    Mike

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  • 0

    The fluorescent lights in the offices on the mezzanine nearby flicker when the machine pulls a high load.

    Before un-routeing a load  of cable, if you can, see how much the voltage on the wiring to the lights is wobbling about - it may be good old fashioned voltage drop, and 'conducted emissions' rather than a radiated EM .
    If the motor draws 30A phase when up to speed it may be trying, and failing, to get a few times that during start up and changes of speed . If so, Mr Ohms law may be enough to explain a lot of the rest. You will need a voltage logger or scope (can be hired) or at least a meter with a very fast response or max/min hold.

    Is it easier to lay in a new main for the lights and delicates , rather than the motor ?
    Mike

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