A transformer is used to control and adjust voltage and current levels in alternating current circuits. They are used from the point of generation all the way to the point of use. Utilities utilize large step-up transformers to increase the voltage after generation to efficiently transfer power over long distances. As the energy nears the point of use, it passes through a number of step down transformers to limit the available power and lower the voltages to safer levels.

Step-Up Transformers

Step up transformers are used to increase the voltage before electricity transmission to reduce the line losses. Electrical power is the product of the voltage multiplied by the current. Pressure and flow are analogues to voltage and current and are more readily visualized. With higher pressure (voltage) a smaller pipe (wire) is needed to supply the same power level, and as with fluid flow resistance to flow causes a pressure (voltage) drop. It is therefore advantageous to transfer power at high voltage (pressure) levels to minimize the loss cause by resistance to the flow of current (or fluid). Generally, the electricity is produced at 11 kV and transmitted at 22 kV or 44 kV. Long distance transmission lines may exceed 100 kV and in China UHV transmission lines operate up to 1000 kV.

Other applications for step-up transformers include automotive ignition coils, certain lighting ballasts, power transformers for vacuum tube amplifiers, and microwave oven transformers to name but a few.

Step-Down Transformers

Step down transformers, as the name suggests, are the opposite of step up transformers. At the end of the transmission lines, the high voltage must be lowered to safer values. This occurs through a series of substation transformers which lower the voltage and reduce the available power capacity as the service approaches the point of use. In North America, the electric service entering our homes and light commercial buildings is referred to as split phase with two lines each separated 120 V from ground. This provides 120 V service from each line to ground and 240 V service between the two lines to more efficiently power high consumption devices like electric ovens, clothes dryers, and air conditioners.

A final reduction in voltage occurs within the appliances we use or within the wall adapters that power our devices. Common voltages include 24 VAC for our thermostats, 12 VAC for halogen lighting, and a range of other voltages for small electronic devices.

For all of your transformer needs or questions, contact the experts at Foster Transformer today!