On 2014-01-13, David Billington wrote:
On 13/01/14 12:11, Lloyd E. Sponenburgh wrote:

[ ... ]

That it's a remote possibility, I won't deny. But such switches typically
serve for years to decades without a malfunction in the dusty, dirty,
swarf-filled environments in which we use them, and it's dumb to think of
the average home craftsman's going to the trouble to re-wire, retrofit,
and otherwise jigger-up his equipment with low voltage contactors and
safety circuits. That some would or even could is beside the question.

What's the benefit of a low voltage contactor and safety circuit? I have
various equipment with safety circuits and they use either the 230V or
415V supply for the contactor and safety circuit.

Routing the wiring around the machine tool to provide both the
"stop" switch at the end of cut condition, and multiple "stop" buttons
within convenient reach if something goes wrong, plus more than one
start button as well. With no high voltage on those (if design makes the
back easy to contact). You can use smaller gauge wire to route it where
you need it without adding stiffness to the machine's movement. (I
would like stop and start buttons on the moving arm of the H/V bandsaw,
so I don't have to bend over as far to reach the power switch.) But
this is just me. :-)

Even the Chinese 12x40" lathes have relays and a transformer to
provide the control voltages at 24V instead of the 120 or 240 VAC (the
latter more likely for that large a lathe). And -- the wiring might be
for 480 VAC as well, depending on where the machine will be installed.
Just move some jumpers to change operation from 240 VAC to 480 VAC, and
the control buttons don't get any more voltage than 24 VAC.

I discovered how this was set up when I helped a friend convert
his to a three-phase motor with a VFD. Even added a "jog" feature to
enable rotating the chuck until the proper wrench socket is facing out. :-)

And the VFD actually uses even lower voltages -- 5 VDC or at
worst 10 VDC for all the signal leads.

Enjoy,
DoN.

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