The no-volt-release switch stopped latching on my single-phase planer thicknesser. The motor is under 1.1kw (1.5hp) and I understood that I would be able to drop in a generic switch.
However now that I have come to wire in the switch I find my motor has three wires (plus earth) and not the simple live and neutral I expected.
In case it's useful, here are some pictures of the old switch and how it was connected:
Unistop seem to be out of business and a like for like replacement not available.
Note the yellow jumper. I have no idea what these letters mean.
The motor casing tells of a circuit diagram to be found inside the terminal block but alas there is nothing there, here's a not particularly helpful picture of inside the terminal block:
The canister on the right contains a capacitor which is part of how the motor copes with a single phase supply.
I've done a bit of work with this detaching everything and doing continuity testing to establish the following circuit diagram for the motor (apologies for the dodgy art skills):
What I think we have here is a Wye arrangement very similar to this arrangement, the diagram on the left below..
The difference on my motor is that the bottom of the three coils (brown-brown) is connected by thinner wire and has a far higher resistance. I understand this may indicate a starter coil which is possibly connected to an internal centrifugal switch leaving the upper two coils to run the motor slightly out of phase due to the capacitor.
So far so good I hope, but I'm not 100% sure how to connect the Brown, Black & Blue cables that come out of the terminal block to the Brown and Blue ones coming from my single phase 230v mains power.
I can tell you that ignoring the black wire and connecting live and neutral to brown and blue doesn't work, the motor judders back and forth and doesn't get started.
I can also tell you that connecting black to mains neutral and the other two wires to mains live instantly trips my electrics.
So... how do I wire this thing up?