As noted, generally, 240v is the nominal voltage supplied by the Power Company nowdays for residential and light commercial. You should measure your incoming voltage to see what it is. Many appliances are rated at 230v, thus a motor that draws 15 amps at 230v as specified on the data plate, will draw slightly less (about 14.4amp) at the 240v your garage is supplied with. If the equipment is marked either 220v, 230v or 240v, it should work quite nicely on the 240v you most likely have in your garage and home.
Some equipment will specify a certain amp draw at a certain voltage at 60 hz and a different amp draw at 50 hz. If so, then you would ignore the 50 hz specs as there is none in the US. For reasons I do not understand, most of the rest of the world uses 50 hz while a few areas, such as the US, Canada, Saudia Arabia, and the western side of Japan, use 60 hz. To me, 60hz makes more sense, since there is 60 seconds in a minute, 60 minutes in an hour....... There used to be a few odd cycle power plants in the US, but I think they are all gone now. Buffalo, NY at one time had 25 hz power and there was a machine shop that used it for many years after everyone else had converted to 60 hz.
As a side to this, the reason for the power shortage in Japan right now, with the nuke plant out of service, is that Eastern Japan, where the plant is located, uses 100v 50 hz power, this is the most populated area of Japan. The Western region uses 115v 60 hz and as such, the grids are not and cannot be interconnected. There is talk of some industries moving their plants to the western region where there is sufficient power to operate them and avoid the rolling blackouts in the east.
If you have equipment marked 115/230v then it can be operated on either voltage, by using the correct plug on the cord, and rewiring the internals as specified on the data plate or diagram. This is common on electric motors, which will have diagrams on the data tag showing the internal wire connections and jumpers necessary for each situation. Generally you are better off sticking with the higher voltage if you can, but on things like my portable air compressor, I leave it set up at 115v so I can take it away from the shop to use it.
For giggles, here is a list of countries of the world and the type of power they use.
http://www.kropla.com/electric2.htm
This is a little better info
http://users.telenet.be/worldstandards/electricity.htm
Most of the rest of the world uses a single voltage for residential use. In the US and a few other places, we use a unique system where we have a center tap transformer, which supplies 240v out of the end taps, and the center tap is the neutral. If you get 240 from the two ends of the windings, then it stands to reason that you will get 120v if you go from either end tap to the center tap. Most countries would use transformers without the center tap, and all voltage supplied is at one voltage. No dual bus circuit breaker panels are needed. Everything coming out of the walls to run lights, the toaster, the alarm clock, everything is at the higher 220v (or whatever they use). Heavier duty appliances and equipment require heavier wiring and heavier plugs and receptacles, but the voltage remains the same.
Charles
