They do not convert electricity. They simply allow a dual-voltage appliance, a transformer or a converter from one country to be plugged into the wall outlet of another country. The plug of a Continental European appliance will not fit into an outlet in a foreign country without an adapter.
Converters and transformers both step up or down the voltage, but there is a difference in use between them. Converters should be used only with "electric" products. Electric products are simple heating devices or have mechanical motors. Examples are hair dryers, steam irons, shavers, toothbrushes or small fans. Converters are not designed for "continuous duty" and should only be used for short periods of time (1 to 2 hours). Additionally, most converters can only be used for ungrounded appliances (2 pins on the plug). Converters must be unplugged from the wall when not in use.
Transformers also step up or down the voltage, but they are more expensive than converters and are used with "electronic" products. Electronic products have a chip or circuit. Examples are radios, CD or DVD 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 continually for many days. The advantage of converters, however, is that they are lighter and less expensive.
Computers are electronic devices and therefore they must be used with a transformer, unless they are dual voltage. Fortunately, most laptop battery chargers and AC adapters are dual voltage, so they can be used with only a plug adapter for the country you will be visiting.
Transformers are sold in various sizes based on how much wattage they can support. Therefore one must pay careful attention to the wattage ratings of the appliances to be plugged into a transformer. The wattage rating of the transformer must always be larger than the wattage rating of the appliance to be plugged into it (plus a 25% buffer to allow for heat build-up in the transformer or converter). When plugging multiple items into a power strip, then into the transformer, you must calculate the combined wattage of all appliances and the power strip, then add an additional 25% to that total.
The appliance’s voltage and wattage requirements are listed on the manufacturer's label located on the back or at the bottom of the appliance. In some cases, the voltage and amperage will be listed, but not the wattage. If this is the case, simply multiply the voltage by the amperage rating to find the wattage rating (e.g. 230 V * 1 A = 230 W).
Below is a list that gives an idea what the wattage of common appliances is. Use this as a guide only. Always check your appliance first !
- 75 watts: small, low-wattage appliances such as radios, CD players, heating pads, and some televisions.
- 300 watts: larger radios, stereo consoles, electric blankets, sewing machines, hand mixers, small fans and most TV sets.
- 500 watts: refrigerators, hair dryers, stand mixers, blenders and some stereo equipment.
- 750 watts: projectors, some sewing machines and small electric broom type vacuums.
- 1000 watts: washing machines, small heaters, some coffee makers and vacuums.
- 1600 – 2000 watts: dishwashers, most appliances that have heating elements such as toasters, electric deep-frying pans, irons, and grills.
- 3000 watts: heaters and air conditioners.
Transformers and converters only convert the voltage, not the frequency. The
difference in cycles may cause the motor in a 50 Hz appliance to operate
slightly faster when used on 60 Hz electricity. This cycle difference will cause
electric clocks and timing circuits to keep incorrect time: European alarm
clocks will run faster on 60 Hz electricity and American clocks will lose some
10 minutes every hour when used in Europe. However, most modern electronic
equipment like battery chargers, computers, printers, stereos, DVD players, etc.
are usually not affected by the difference in cycles and adjust themselves
accordingly the slower cycles.