Electrical noise created by 3ph machine

Question

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.

mapj1 · Answer

A 20A lighting circuit sounds a bit on the high side, though 16A driving ES lamp fittings used to be quite common in the days of big bulbs . (1960s 250W filament lamp anyone ?) Would be typical if the light fittings plugged in with 13A plugs, but then it is a socket circuit with switches, not a lighting cct. In any case not against the rules, just odd. 
 But, if it is 1.5mm it may be a bit undersized depending on cable grouping factors and so on, (or if you prefer, a bit over-fused), but in practice most unlikley to be an issue - and it may have been done to avoid a need for C or D type breakers rated at a lower current. 
 Mike

Electrical noise created by 3ph machine

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