ELECTRIC TRANSFORMERS

Transformers vs. Plug Adapters

PLUG ADAPTERS will allow you to change the plug style -- but NOT the voltage! So, these should only be used on devices that accept a range of voltage, usually 110 - 220. It MUST say it on the device. If it doesn't, don't chance it.

TRANSFORMERS, on the other hand, change the voltage. Note that many devices come with their own transformer, commonly referred to as a "power brick". That rectangular block on old phone charging cords is a transformer. Such device transformers not only change the voltage, but also change it from AC (alternating current -- the kind you get from a wall socket) to DC (direct current -- the kind you get from a battery).

Other transformers just change from 220 volts AC down to 110 volts AC, so that you can plug in an American appliance in France, for example.

Two Types of AC Transformers

It's important to know that there are two different classes of transformers, switching and coil, and they use completely different principles and produce different kinds of power. Switching transformers are just circuits. They can be identified by their light physical weight. They can produce AC power, but it is usually limited in terms of max power (Watts, or amps) and by the fact that the power is electronically noisy. So, for devices that require high power and clean power, they don't work well and can either burn out or ruin the appliance. The exception is usually heating appliances, like hair dryers, which don't care if the power is dirty. As a result, they are usually sold for this application -- with a warning not to use it for others.

The other type can be distinguished by being physically heavy. They use induction; wire coils are wound around a steel core. These are far more versatile. Big ones can produce relatively high amounts of power (Watts, or amps), and the power is clean. That said, you can still overload them, so it is vitally important to know their stated power limit and to compare that with the power rating on the appliance you want to plug into it. Stay well within the power range, and such a transformer can make an appliance like a sewing machine run for years, trouble-free. However, some appliances, like a KitchenAid or VitaMix, are super power hungry, sometimes needing more than ten amps. That's a lot, and it is difficult to find a transformer capable of producing it. Also, be aware that these transformers can be expensive, far more than the cheap switching kinds. When treated right, though, they will last forever. The price, and the physical size and weight, will be proportional to the power output.

Finally, be aware that coil transformers consumer power when they are plugged in, even if you don't use the other side for running an appliance. So, don't leave them plugged in. This is also why it makes no sense to build them into your house circuitry so that you can have a foreign plug right in the wall.