Battery and Motor

Curious007

I saw 15 Amp motor which runs on 120 VDC with 5500 rpm [This motor was attached to Miter Saw tool]. I'm not sure what's HP of that motor, but I read 5.5 HP, however the size of motor is around 6 inch long and 4 inch diameter (Is it possible this small motor have 5.5 Hp? And can we calculate torque of the motor based on above known facts?).

Now my other question is : Can I run this 120 VDC motor using this 20 Volt DC with 3 Ah rating battery? If so how long I can run this motor using it?

Thank you.

russ_watters

Well, 15A at 120V and 95% efficiency would be 2.3 horsepower.

I seem to remember that vacuum cleaner manufacturers play games with horsepower ratings, so it wouldn't surprise me if circular saw manufacturers did too.

Curious007

May be that was mistake of Shop guy who put 5.5 HP sticker on it.

But other thing is can we run that motor using 20 V DC battery with 3 Ah rating? for 1 or 1 minutes?

sophiecentaur

A 120V motor will not work on 20V. I doubt whether, on only 17% of its rated voltage, it will even rotate at all. Basically, with 17% Volts, you could expect to get just 2.8% of its power (i.e. 17% of 17%) - even if everything else was perfectly pro-rata - and there is a threshold below which nothing will happen. You might expect about 2.5A to pass.

BTW, the current that the motor will pass is determined basically by the supply volts - too few supply volts will just not make enough current flow. A low voltage motor is designed with much fewer coils of fatter wire (as in a car starter motor).