How do transformers work? By Tom Tate

If we were to ask you to de- scribe KEC’s system, you might say, “Poles, wires and those round grey things.” Round grey things? That is often the de- scription given for transform- ers, the pieces of equipment crucial in converting electricity to a voltage that is safe for use in homes and businesses. So, how do they work? First off, transformers are nothing like those creations of

the silver screen. transform They

don’t transform from vehicles to incredible combat robots. Instead, they

the

voltage of the electricity that passes through them. Time for a little electric system 101. Electricity loses voltage as it is transmitted due to the resis- tance in wires and other com- ponents. As a result, higher voltages are used to offset these “line losses,” as we call them. It all starts at the power plant. There, generators pro- duce electricity at very high voltages and use transformers to step up this voltage, often to 67,000 – 138,000 volts. Since the power plants are far away, these voltages are necessary to survive the trip over the sys- tem to where it is needed. Transmission lines connect to substations brimming with transformers and other control gear. Here is where the trans- formers step down the voltage to safer, more manageable lev-

els. Depending upon the dis- tance involved to the furthest member and the amount of load served, distribution volt- ages can range from 7,200 to 24,900 volts. A couple more step-downs and the electric- ity arrives at your home at 440 volts. This is quite different from the original voltage. Regardless of the shape and size of the transformer, they all work in the same manner. Transformers have two sides, a high-voltage side and a low- voltage side. In normal opera- tion, electricity flows into the transformer on the high-voltage side, where it goes into a coil of wire usually wound around an iron core. As the electricity flows through this coil, it cre- ates a magnetic field that “in- duces” a voltage in the other coil. Here is where the magic (aka physics) of transformation takes place. Each coil has a different number of turns. The greater the number of turns, the higher the voltage. The coil on the high side will have more turns than the one on the low side. As a result, the voltage in- duced on the low side is less. Then transformation occurs. Transformers aren’t just lim-

ited to utility use. They can be found everywhere in our daily lives, even if not so obvious as those on KEC’s system. The best example is the charger that all cell phones and many

other electrical devices come with. These small cousins of utility transformers basically perform the same function. Charging your cell phone with 120 volts will fry it instantly. So, the charger converts the volt- age to a more tolerable 5 volts or so. Take a moment to look around your home and see just how many of these miniature transformers you have. You might be surprised!

It is important to note that transformers work in both di- rections. Electricity flowing in on the low side is stepped up to the voltage of the high side. This is why KEC educates members on proper connec- tion of home generators. A gen- erator feeding 220 volts into a residential transformer will produce whatever voltage the transformer is rated for on the other side, creating a deadly risk for our line crews and your neighbors. So please, connect your generators according to the manufacturer’s recommen- dations. Or give us a call at 1-800-535-1079 for advice. It’s always best to be safe.

Tom Tate writes on cooperative issues for the National Rural Elec- tric Cooperative Association, the Arlington, Va.-based service arm of the nation’s 900-plus consum- er-owned, not-for-profit electric cooperatives.

Crisp morning at United REMC, Markle Indiana. Photo by Cindy Barton. 4

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