# 240volt vs. 120volt

For a first order approximation, under 'steady-state' conditions, you _are_ basically correct. Needless to say, considering only 'steady-state' conditions is not really meaningful for analysing a table-saw. :)
The differences occur due to a variety of 'lesser' factors, including: 1) parasitic losses that are not directly related to applied voltage, 2) "stiffness" of the power _source_. 3) speed of response to varying load conditions -- when a motor is trying to play 'catch up' to an increased load, it draws more power than it does handling that same load at steady-state. The longer it takes to get back to steady-state, the more 'excess' power consumed. 4) 'non-resistive' (e.g. 'capacitive', and/or 'inductive') components of the load. (capacitance, inductance, and resistance react in _different_ ways, in parallel vs series circuits -- different from _each_other_, I mean. e.g. in series, resistance 'adds', but capacitance 'divides') 5) 'power factor' -- pretty much equivalent to #3

More commonly, it is the other way around, a device is slightly _more_ efficient at the higher voltage. On a _good_ day, it may approach 2%. :)
However, there are no 'guarantees'. It depends, _entirely_, on the design of the specific device.

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Consume more power? The first guy to respond to the question was spot on. Has everybody who attemps to reply actually run a bunch of tool on both 120 and 240? Same tools? Tried both ways? If you use a gawdawful heavy cord direct from the service panel, maybe you couldn't tell the diffence. In the real world, with similar gauge wiring, you'll find the saw will start quicker and bog less. Since it bogs less, it runs cooler. IMHO
rhg

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Robert Galloway wrote:

In the real world if you're using the same gage wiring for a 240 volt circuit and a 120 volt circuit that has to carry twice the current then it's time to sue the electrician.

--
--John
Reply to jclarke at ae tee tee global dot net
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120 volt light circuit maybe 14-3/G Most of us have shop circuits wired with 12-3/G and an occasional 10-3/G. 12-3/G goes most places in my shop 120 or 240.
rhg
J. Clarke wrote:

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Robert Galloway wrote:

You're supposed to size the wire for the current and the length of the run so that the voltage drop at max load is allowable. If you do that then saw should not be "bogging" due to voltage drop in the wiring under heavy load.

--
--John
Reply to jclarke at ae tee tee global dot net
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Correct. As I mentioned in a different post, in an ideal world, every application of a power tool would have copper coming to it of such size that the maximum load of the tool wouldn't produce a discernible voltage drop. This would include the cord provided by the manufacturer of the tool. In the real world, I've been happier with tools running on 220. I've spend a lot of time with most of them both ways. You pay's your money and takes your choice. My advice is, if the tool stays in one place all the time and 220 is handy, use it. YMMV.
rhg
J. Clarke wrote:

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More consumption in the 240 volt mode. Makes sense. Doesn't work out that way. The rotating motor functions as a generator. Its generated emf opposes the supplied emf. Its ability to counter the supplied voltage is what limits the net draw. If there's voltage drop in the line, (which is more pronounced in the 120v mode) then the motor is less effective as a generator, less effective at opposing the applied emf and generates more temp rise. Motors run best at full rated voltage. However you want to supply this, the result is the same. On 120 volt, use the largest gauge wire. For a given gauge, 240v will do a better job of keeping your motor spun up to the full rated RPM and therefore do the best job of generating counter emf.
bob g.

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The actual motor wire carries the same current on either voltage. You are changing from parallel to series connection of the windings. The drop mentioned is in the feed wire. If it were very large wire, the saw wouldn't know the difference, but when more current is drawn and the saw starts to bog down, then the current goes up even more and things snowball. By keeping the voltage up by drawing less current on 220 and having less sag, you allow the motor to do its thing and produce rated power at rated current.
At lower voltage (sag) and higher current, heating rises in the motor because of IR drop in the windings. This is true at either voltage, but starts at higher loads because of less drop in the feed.
Wilson

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Be sure that the motor is capable of using 220 volts before changing. Larry

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Every answer you get will be academic. The failed capacitor has nothing to do with what voltage you run. The best reason to run 220 is to be able run more tools on the feed without having to increase the feeder wire size.
Bob
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Including yours? <evil grin>

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On Sun, 13 Jun 2004 00:36:05 GMT, Brandt in western Canada
I have a 1 HP-110V Crapsman TS, whenever I saw hardwood lumbers the circuit breaker trips. I also encountered the tripping problems with my 1-1/2HP-110V compressor whenever the compressor loading. I rewired both machines to 220V and the problems gone forever.
I learn these tips from helpful posters here. By rewiring it to 220V you really have nothing to lose.

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As I understand it, your single pole (120v) 20 amp breaker trips under a heavy load, more than 2400watts. By rewiring to 220 (or 240) volt, you install a 2-pole breaker, probably 20amps PER leg. That kinda makes you supply equivalent to 40 amps (~4800 watts) . Supplying the saw with as much as double the current, certianly would make the breaker trip less.
loadOn Sun, 13 Jun 2004 11:49:07 -0600, in rec.woodworking you wrote:

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