Wiring diagram for 3 phase contactor start up

[Zhevster]

Hi all, I have two three phase sanding machines that both have there own contactor start up. Both work fine. I have connected a dust extractor to them both. That also has its own contactor start up ad works fine. Its also 3 phase. How can I wire the the extractor to be triggered by either sanding machines?

 

[Lucien Nunes]

The extractor starter can be controlled by normally-open volt-free contacts under the control of the two sander contactors, wired in parallel, so that there is no electrical connection between the circuits of the three machines. These could be in the form of an N/O auxiliary already built into the sander starters, or the contacts of a pair of relays energised in parallel with the sander contactor coils.

You would need to risk-assess the operation of the extractor under external control, and label any units energised from multiple sources (the sander starters if the extractor control circuit enters them, or the intermediate relay box.