The voltages entering your home are called secondary and they are either single (or two) phase 120/240 VAC as found in the US or three phase 127/220 VAC. Both are 60 Hz.
Single/two phase power is obtained from a single secondary winding on the power company’s step down transformer. The transformer is center tapped so that we get two high side or line voltages along with the neutral that connects to the center tap.
After passing through the circuit breaker panel, one line and one neutral form various branch circuits that are used throughout the house for lighting, plug-in appliances, etc. Regardless of whether line 1 or line 2 is used, these circuits provide 120 VAC. Larger appliances, such as an oven, operate from the 240 VAC provided by line 1 and line 2. The line to line voltage is 2 times the line to neutral voltage.
In the US, this is called single phase power, and both lines 1 and 2 are provided along with the neutral. In Mexico, smaller houses may receive only line 1 and this is called single phase power. When both lines 1 and 2 are provided, it is called two phase power.
In Mexico, the power company (CFE) also distributes three phase power. In this case, their transformers have 3 secondary windings. One side of each of these windings are connected together to form the neutral. With three phase power, the line to line voltage is 1.732 times the line to neutral voltage.
So, we can have three different line to neutral branch circuits providing 127 VAC, three different line to line circuits of 220 VAC and a three phase 220 VAC circuit suitable for larger motors used for pool pumps, etc.
Our first house in Mexico was in a neighborhood that had three phase power. All the houses used two phase or multiple single phase meters except ours which had a monstrous three phase meter. At one time, all three phases may have been used for the original pool equipment, but this had since been abandoned and only two of the three phases were wired to the house. In general, you cannot tell whether your power is coming from a two phase or three phase transformer without measuring the line voltages, because the wiring will appear the same.
Any decent appliance in North America will operate from a voltage of 120 +/- 10% or 240 +/- 10%. The 127 and 220 volts found in three phase Mexico power are within these ranges, so using US appliances in Mexico should work just fine.
The information on this website and much more is available in the form of a downloadable PDF Ebook available for a nominal charge. If you are interested in seeing the contents and/or ordering a copy, please follow the link to the right.