The invention of the electrical transformer focused on the conversion of one voltage to another. It did not deal with the issue of frequency. As electrical devices have increased in complexity,

Today, there are 175 countries that have a 50Hz frequency and 45 other countries that use 60Hz. Within the two frequency groups, there are numerous voltages: For an American manufacturer of

The worlds smallest voltage and frequency converters to convert 200-240 Volts, 50 Hz to 120 Volts, 60 Hz. Now you are free to use your US-Appliances in any country. Check it