CDH -



As a sorta related question - I have a Chinese 1-1/2 HP motor on one of my machines, and it has worked well for the last 8 years. It is convertable from 110-V to 220-V, & back again, by moving two small copper connector plates (or bars) where the power comes into the motor.



I know this works because I have done it, but danged if I understand WHY it works. Could you give me a bit of insight into what is happening when I move those plates (bars)? It seems almost as if I am rerouting the current from Series to Parallel or vice-versa. Is that what's happening?



Thanks



Alberta Canuck

You are exactly correct.

There are actually 2 windings (coil) on that motor. Each winding is sized for 110-120VAC nominal voltage across them, end to end. With the jumpers in one position, the windings are in parallel, and you hook your 110VAC power to it, so each winding gets its required 110 VAC.

Now, change the jumpers, and the windings are connected in series, or end to end. Since the voltage drops evenly (as even as the thicknes and composition of the copper wires anyway) along the length of the (now one) longer winding, each 'half' sees half the voltage accross the whole thing, and you guessed it, you put 220VAC accross it.

When correctly configured, the motor produces exactly the same amount of power (1.5Hp in your case). The difference is that, using my handy deck reference, it draws 20 Amps of current (115VAC nominal, per my book), or 10 amps @ 230VAC. Different motors will pull slightly different amounts of current, but those are representative numbers I use every day to size wiring and circuit breakers for motor operated valves and pumps here at work.

The advantage is that, since heat generated changes as the SQUARE of the current passed through that same wire, half the amps gives a quarter the heat buildup and will lengthen the life of the motor insulation A LOT!

Hey guys, is this questions for machinist, or electricians??????

Lot's a good info regardless.

Thanks a bunch CDH, that explains a lot.

So, if I am getting this straight, the motor is actually working not only as an engine producing torque, but also as a power "converter" which converts 110 VAC to 220 VAC (at half the amperage) by routing it diffently across the windings? Kind of a neat way to get 220 VAC power off of a standard 110 VAC line, if that is what is happening...

Contrary-wise, if I was to use a 220 VAC power source, and reverse the jumpers, I'd convert it to half the voltage (110 VAC) at double the amperage. Right?

Thanks a lot!

Alberta Canuck