Guide to Electrical Equipment for Travelers/Transformers
Transformers are used with "electronic" products. Electronic products have a chip or transistorized circuits. Examples are radios, CD or cassette players, shavers, camcorder battery rechargers, computers, computer printers, fax machines, televisions, and answering machines. Transformers can also be used with electric appliances and may be operated continuously for many days.
Different transformers are available for appliances of different power ratings. Most products have the power printed somewhere on them, although some products list only amps. A rough conversion for the USA and other 110 V countries is 1 amp equals 100 watts, and for European and other 230 V countries 1 amp equals 200 watts. The power of the appliance must fall within the range of the converter or transformer being used (allow a margin of at least 10 watts).
Computers are electronic devices and therefore they must be used with a real transformer. It appears that there may be other conversion methods around which may damage electronic equipment. Some PC power supplies have a voltage switch, on the back of the case, for 110 V or 220 V — this should never be set incorrectly, and should always be checked if a PC has come from an unknown source or may have been tampered with. Laptop battery chargers, and AC adapters generally have a universal input which can take a wide range of voltages without manual switching. In general, if an appliance has an input that can accept the local voltage, it is generally better to connect it directly (using a plug adapter or adapter lead if needed) than to use transformers or other forms of voltage conversion.