Can someone help me please. I have the electrical diagram for connecting the power of an object. The main switch is 63A 4P threephase.I want to add three differencial relay 40A 4P which have the module for 3phase.But i cant understand in logic.How can i connect the cable after main switch that have 4 wires L1 L2 L3 N,with 3 differential relay which have also 4 terminals each one.So they have in total 12 terminals (3 x 4),while we have a three phase cable with 4 terminals(without ground).Please,can someone explain me this misunderstanding?Thanks (Attached by this question is a photo of the electrical diagram)


  • Are you powering different devices? if you are powering a single device you do not want to use separate relays.
    – Ed Beal
    Dec 28, 2016 at 14:07
  • I think this should be on Electronics.SE
    – Machavity
    Dec 28, 2016 at 18:19
  • 2
    @Machavity This does not belong on Electronics.SE. They would close or migrate it immediately. Unfortunately, this question is not a good fit to any stackexchange I know of.
    – DoxyLover
    Dec 28, 2016 at 20:12

1 Answer 1


I'm very dubious that you should be the person responsible for connecting anything that eats 40 or 63 amps of 400V 3-phase power if you are asking this question. That is some VERY serious power and a properly trained electrician is likely a very good investment in being sure that it works safely and correctly.

But, to answer your question, each wire from the main relay needs to become 3 wires to feed the 3 relays - that can be done via 4 insulated buss bars (1 in, 3 out, each) or suitable junctions that securely join the 4 wires and are adequately insulated for 400 volt service.

Evidently the neutral and one phase also need additional wires to the devices on the right of the diagram.

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