Submersible water pump relay question
As far as I know, all the switching for these is done at the control box. Rather than a centrifugal switch, I believe the relay is simply a fixed time-delay contact. 

But I consider them archaic these days - For single-phase supply, I buy 2-wire pumps, and would replace any 3 wire pump with a 2-wire pump when the 3-wire pump stopped working. The arguments in favor of 3-wire have become much like arguments in favor of a buggy-whip to make your automobile go faster...

If 3-phase supply is available that's a whole different animal, but it's uncommon for residential applications where I live.