How Do Electrical Transformers Work?

The purpose of transformers

Electrical transformers exist in our everyday life for the transformation of electricity from high voltage into low voltage. They can also act in the opposite way to step up voltage. In fact there would be no way possible for you to read this if not for a transformer of many sizes to "transform" the electricity that enters your home to the computer you are now using. The most common type of transformer is the one that is hanging on the pole or on a pad from the power company that brings electricity into your home.

Structure of transformers

The transformer is made up of many windings of insulated wire called coils. These coils are insulated from each other by a thin coating of varnish. If they were not insulated they would be just a large wire with no work purpose. The insulation helps to create a very long conducting wire. Electricity that enters your home is known as AC or alternating current. This current goes from zero to 120 volts, 60 times a second or 60 Hertz.

Windings

A transformer can only operate with AC as the electricity must wave or alternate for the windings to do their job. There are two sets of windings in most common transformers. There is a high side or high voltage connection and a low side or low voltage connection. These windings are electrically insulated from each other, they do not have a conduction path. It is the AC, or alternating current, that "induces" a current into the other winding.

Voltage ratios

Let's take the transformer on the pole outside your home. All transformers have a ratio--the number of windings the high and low sides have. Let's say that the voltage on the high side of the power pole is 12,000 volts and the power coming from the pole transformer into your home is 120 volts. The ratio of the step down transformer would be 100 to 1. In other words for every 100 windings on the high side there is only one winding on the low side.

Step-up and step-down transformers

Every transformer for the most part can be used as a step-up or step- down transformer. That is why when the power goes out most electrical utilities want you to have a disconnect switch in place if you use a generator. That generator may be giving you 120 volts but if plugged into the pole transformer it can generate 12,000 volts on the high side and injure a utility worker.

Resources

• Information on sizes and different types and other cool energy stuff