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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 | ||
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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! | |||
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Hey guys, is this questions for machinist, or electricians??????  Lot's a good info regardless.  | |||
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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 | |||
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Quote: I come from a family of electricians and this stuff gives me headaches. I would like to add something to one of your previous posts, 460 3 phase is not the most common form of 3phase, 220 is. Where you usually see 460 is in big shops where the economy of using very high voltage is worth it to reduce electrical costs. They do the same thing now in offices where they supply 277 volts for the florescent lighting. something to do with the ballasts. Alot of Office buildings in Manhattan use 460 for the big(100hp+) motors they use in the elevators. Maintanance of them was one of my fathers jobs when he worked at the Met Life Tower in Manhattan. He showed them to me one time and they were frikkin' huge! As for the 220 volt thing for motors over 1 hp, I'll agree with you except when it comes to portable equipment like roll around Aircompressors. If you have to take it somewhere to do a job, 220 is rarely available in the form of outlets. When we got one, John(my brother, Local 3 electrician) had to put an outlet in the garage. Toolmaker, BTW, you can get motors to ten horse in 220 single phase, it's just that they're very uncommon. The biggest you normally see is 7.5hp on certain air compressors. | |||
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"Kind of a neat way to get 220 VAC power off of a standard 110 VAC line, if that is what is happening..." Just the opposite, you are getting 110 VAC off of a 220VAC line... "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?" Just don't put 220 VAC power to it with the jumpers in the 110 VAC position...  You will learn quickly about the 'smoke theory' of electronics and electrical equipment. They all operate on smoke, and if you let the smoke out, they quit working! The analogy of water moving through a pipe has long been used to explain the relationship of voltage, current, and resistance. It works most of the time...voltage=water pressure; current=moving water; resistance=friction with the pipe walls, pipe size=wire size. A pipe of double the size can carry twice the water(current) at the same pressure(voltage). Conversely, if you double the pressure in the same pipe, you move twice the water. (220 V)Make the pipe twice as long and you need double the pressure to move the same amount of water. (110V)2 pipes in parallel can carry twice the water at the same pressure. Confused yet? | |||
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Well. now I am really confused. I don't have 220 VAC in my shop. Nor do I have any 220 VAC outlets anywhere on my premises. I plug my machines into the same wall sockets one would use for a lamp. This particular lathe WAS in my other shop which did have 220 VAC, which is how I know the motor works both ways, but on this site there is no 220. So, don't see how I could be converting 220 VAC to 110 VAC. But, the motor is running just fine. Que paso? Alberta Canuck | |||
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Quote: All Bridgeports I've seen are 3 phase, 1 to maybe 3 HP. Mine is a 1 1/2 HP 9 x 42 Varispeed. Some of the smaller chinese knock-offs are single phase. The advantage of 3 phase is that you can stick a VFD in front of it to control the spindle RPM. Don't worry about the co-ax indicator. Once you do it a couple of times you'll get the hang of it. Kory | |||
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