This may be a duplicate post

Lew
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"DaveC" wrote:

A friend (in USA) with a 220v, 1-phase horizontal bandsaw in his home
machine
shop wants to replace the 1/4 hp motor with 1/2 hp and rewire with
an
auto-off switch (when the blade cuts through the metal).

I always default to using a 3-wire control with contactor, but he
asks the
logical question: "Why?"
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What you are describing is known as under voltage protection.

Safety pure and simple is the best reason for using it.
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Other than the "If the power fails while cutting" answer (which he
says seems
of limited additional value on a saw with auto-stop feature) I
wasn't very
convincing.
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What happens in the event you lose power and as a result you lose
lighting
as well as power to the saw?

Without under voltage protection, when power is restored, the saw
will restart automatically which can be disastrous, especially if the
lights
haven't restarted.

Your insurance company will also like you.
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What are the arguments for using a contactor as opposed to a simple
on-off
switch of equivalent rating?
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See above.


Lew