Jeff supplies an excellent example of a safety interlock designed to prevent
serious injury, because a person can't always predict all the possibilities
involved when a machine stops unexpectedly.
Almost everything in life is a cost issue, but the saw manufacturer knew
that preventable injuries would end up costing them.
Having start/stop controls within easy reach of the machine operator,
locating the electrical service disconnect within sight of the machine, and
more than one level of protection for the equipment, are all considered to
be required protections in a working environment.
They should also be sensible for the DIY home shop worker to utilize in
their machine power circuits.
Having the contactor drop out for a loss of power condition isn't especially
complicated, and not expensive to implement.
Examples of start/stop circuits for magnetic starters can be found here..
see
Simple Magnetic Starter
Deluxe Magnetic Starter
http://www.homemetalshopclub.org/pro...nv/phconv.html
Wiring diagrams for commercial RPCs can probably be found at most of the
manufacturers' websites, as well as here at the ARCO site
http://www.arco-electric.com/
WB
..............
"Jeff Sellers" wrote in message
...
"Ignoramus9394" wrote in message
...
SNIP
If so, then, logically, I need to install similar relays on single
phase equipment as on 3 phase equipment. And yet no one does this with
single phase equipment.
This IS done on at least some single phase equipment....My Delta Unisaw
has
a magnetic switch that works that way. If power is lost, the relay drops
out
and the saw will not restart when power is restored, until ya press the
button again.
I guess the idea is that the machine may not get turned off when power
fails, and you may not be around when power returns.....
Posted FWIW....
Jeff
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