Don't think you should be concerned with UL certification and such.? Induction motors have been around for 100yrs or so and the things that make them fail aren't tested for in UL anyway?
You are only really at risk of burning up your motor cutting sticky materials like aluminium or copper where the swarf sticks in the gullet between the teeth,? Then the gullet can be more than half full, the next time that tooth is asked to cut.?
The new swarf has to go somewhere and aluminium, or copper,? is soft enough to squish out of the gullet into the space in between the blade body and the wall of the kerf, where it welds to the kerf wall and is strong enough to jam the blade. Wood and plastic swarf also squish out, but they're too weak to jam the blade, so just push it off course and you get a crooked cut.?
If the blade doesn't come off the wheels, it will stall the motor.? If you don't cut the power within ~20 sec it will start to smoke, irreparably damaging the motor. When it stalls, the start winding cut in again and the current goes up to something like 7x the running current, the insulation overheats and the windings short out = burnt-out motor.
Because the current is still flowing, if you're out of the shop, like off making a cup of coffee, the motor can catch fire.? Never leave a saw cutting aluminium un-attended.?
Generally this doesn't happen cutting steel as the swarf falls away from the teeth at the exit from the cut, and it's too hard to squish into the space between blade and kerf anyway.? ?The only time I've stalled the motor on steel is when I was testing how much bow weight I could load up.? It would stall quite easily above 12lb bow weight in high speed, but that's way too much weight anyway as it damages the blade.? In this instance stalling is horsepower dependent, so too much bow weight and/or too much blade speed will tip it over the edge.
I burnt out my first motor (cutting aluminium) and the replacement is a 1/2HP 'Capacitor-start/Cap-run' motor,? It has a no-load speed of 1375rpm and is quite stable down to 1300rpm (I'm in 50Hz territory), but the motor stalls the instant it hits 1250rpm.? I don't know whether a thermal overload can be retrofitted to a motor that wasn't built with one, so I'm investigating building an Arduino device to count the motor rpm and cut the power when it hits 1260rpm. Theoretically it's do-able and would give very good control and could be programmed for any rpm.? Cap-start 1425rpm motors will stall at a different speed, as would 60Hz motors of different configurations, but the figure is easy to ascertain with a rev counter.
I don't know of any OEM motors that have thermal overload re-sets, but Grizzly sell replacement motors for machine tools, that I believe, have them. - jv
John Vreede