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I got a 1-phase induction motor (230v/50hz) that was taken from a tile cutting saw that I planned to use in a home made disc sander, the labeling on the machine says it's a 600W motor but the motor itself has no information at all on it.

I am doubting that it's 600W because last night as I was truing up the plywood disc by mounting it and using the motor as an improvised lathe. The motor got incredibly hot from running only 5 minutes or so and I stopped to let it cool down, and to considerif this was going to work at all. I don't think I could put that much stress on a 600W motor (.8HP) by spinning a 24cm diameter piece of 12mm plywood.

It also looks smaller than other 600w motors I've seen, I have a 750w 3-phase motor (400V/50hz) that is much larger and heavier, but I do not know how good an indicator size alone is.

I am wondring if there are some simple ways to determine what kind of power range this motor falls into? Perhaps using a power meter and checking the amp draw while the shaft is spinning without any load? Not sure what kind of draw I should be having for a 600W motor though.

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  • \$\begingroup\$ I don't think you can tell - because the limitation (possibly among others) will be the heat it can dissipate while still being safe and long-lived. This will have been established by the manufacturer with a sizeable budget and technical resources \$\endgroup\$
    – Jayy
    Commented Apr 9, 2015 at 5:27

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The motor of a hand-held tool is often underrated because it's intended to be used intermittently. Sometimes the tool will even say 10 sec / 1 min or something, to make this clear.

It might also not have adequate cooling for continuous use, even if you kept the fan and ducts from the original power tool intact.

You could try running it and measuring the temperature over time, until it stabilises. Using a series of loads (fans) you could find a power level which results in a reasonable temperature rise.

Unfortunately, you might find that there is no load small enough to prevent it from overheating. In designing the cheapest motor for intermittent use, the copper and iron may be too light, or have too few turns. The only way to run it continuously might be to run it at a lower frequency, or a lower voltage.

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  • \$\begingroup\$ OK but it was not a hand tool, but a stationary one, looks like a tiny table saw. Oh and the motor has a typical fan on end like most induction motors I've seen. \$\endgroup\$
    – Dennis
    Commented Apr 9, 2015 at 5:38
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    \$\begingroup\$ Ok that's better then. Try running it for half an hour and finding the steady state temperature for various loads. Measure electrical power, easier than mechanical power. Try ducting the fan, if not already like this, so it blows nicely over the motor. \$\endgroup\$
    – tomnexus
    Commented Apr 9, 2015 at 7:44
  • \$\begingroup\$ I hadn't had time to look at it until last night, but the I checked using a power meter the amp draw of the motor with the plywood plate mounted and without and it didn't even change. I think the fan might be ineffective. Perhaps adding some cooling vanes (radiators) to the metal case would also help. \$\endgroup\$
    – Dennis
    Commented Apr 20, 2015 at 9:02

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