David Lesher wrote:

Vernon writes:

"Depending on the VFD, maybe it has a shutdown function, but don't
depend on it. I'd have a direct 3-phase pushbutton, the latching
kind. [Push in, it stays in until unlatched.] Use an aux contact for the
VFD."

I did not understand this. The VFD manual says to have a disconnect
device but not to use it except in an emergency. Obviously, getting
entwined in rotating machinery is an emergency and trumps trashing the
VFD.

Get a pushbutton, a big industrial one. Allen Bradley comes to mind. They
are basically Legos; you start with the basic button and add contacts of
the type needed.

It should have 3 contacts rated for the full current of the motor. They
will be closed in OUT mode, but open when pushed in. Wire in series
with all three legs going to the motor..

Have a low current 4th contact going to the VFD shutdown connection.

This will break the power feed to your mill when hit, AND send a shutdown
to the VFD. [It may take a while to turn off, however, as compared to the
button. Maybe even as much a second or two; see what the VFD Fine Manual
says.]

This way, even if the shutdown command does not work, the power *is* off.

The shutdown pushbutton will be expensive new. There are millions surplus
but it will be tricky to mail-order same. If you have a surplus place
nearby....

The E-stop switch belongs on the power feed *to* the VFD, *not* on the
motor leads from the VFD, otherwise you just have a "VFD destruct"
button. The diagrams in the VFD manual should show the proper wiring for
an emergency stop.