I have to cut a lot of boards of yellow birch (1'' thick) with my table saw
(120V with 1.5 HP motor). Between each board, I stop my table saw for
approximately 20-30 seconds (just the time to store the pieces and take a
new board) and then, I start again the table saw (I don't have to adjust the
fence). I realised that the motor become hot after 30-45 minutes, so I stop
for a while.
I will wire the motor on 220V soon or late. For the moment, I want to know
if it is better let run continuously the motor or stop it between each
board? Maybe it doesn't matter?
I run a contactor saw all day and I used to run it on 115. Moving over
to 220 will be a great help. Maybe try to do that sooner as it runs the
motor cooler. As far as now, I would run it continuously as the startup
is quite a heat causing bog down. I also imagine that a motor running
under no load cools faster than a motor stopped. Also, make sure the
motor is clean for proper ventilation.
My too cents.
When I have several production boards to rip, I set up convenient
places to get and place the boards and keep the saw running
continuously. Usually I'll take a 5 minute break about every 15
minutes to enjoy some quiet time while sweeping up the sawdust.
If it were mine I would not stop and start it that frequently for a couple
of reasons. (1) That is putting extra wear on the power switch contacts.
(2) It is putting extra wear on the motor start circuit. (3) The motor
"start" circuit is designed to only be in operation for a few seconds and
draws more current than the "run" circuit. This could be part of your
heating problem. Though it may not be significant, you are using more
electricity with frequently starting the motor. Some motors have a fan in
them, by letting the motor run you may cool the motor some while you are
shifting the boards around.
That's the way I'd do it!
If you have the motor running under load for 30 minutes or so, it will
be quite warm to the touch. I would leave it running if for no other
reason, because it is an extra step to turn it off and on. Do be
careful how you handle the cut off pieces as anything droppen on the
blade will fly.
My guess is that it would be cooler to keep it running, as the internal fan
would be working and also the startup load might create more heat?
The other consideration is SAFETY... don't leave it running if you can't get the
cut pieces off the saw table safely..
Please remove splinters before emailing
When an induction motor is first started the motor's windings present
almost a direct short on the electrical feed. As the motor spins up a
"counter EMF" is generated limiting the current flow. Until the motor
is at full speed it draws more current and generates more heat. Safety
standpoint aside, it is better for the motor and cheaper to let it
continue to run rather than stopping/starting it every few seconds.
Think about it. If you leave it running, fan stays running, you avoid
dumping that start current from the capacitor and you give the
centrifigul switch a break. for twenty seconds leave it running, if
it is guarded and can safely be left on.
I've never heard of an overload tripping from no load running but it
sure happens with high cycle startups.
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