Monday, August 5, 2013

The Electrifying Truth

Would you know how to create electricity using something like this? Honestly, when I first arrived at the museum, I thought it was a modern art piece. This armature core (about 93" x 48") sits behind the museum as a part of our outdoor mining exhibit, but I have heard countless visitors return inside just to ask how this giant actually works.

The principle for the armature was first developed by English scientist, Michael Faraday, when he made the discovery that if a loop of wire is moved up and down between the two poles of a magnet, a current of electricity moves through the wire. His discovery was improved upon to create something that would produce electric currents. The early AC transformer in the museum's outdoor exhibit works on a modified version of this early discovery. These types of generators produced a large amount of amperage (how quickly the electricity is moving) at a relatively low voltage (how much potential electricity there is).

An armature is made up of a coil of copper wire wound around an iron or steel core. The core is what remains outside the museum. This entire piece is placed in a magnetic field, which is produced by one or more permanent magnets. The armature is then rotated in the field by an outside force, which causes the coil to cut the lines of the magnetic field, just like in Faraday's early experiment. This action creates an alternating current of electricity within the coil.

The next step in this process is finding a way to harness the electricity generated from this process. Wire cannot be directly attached to the coil, because the constant spinning would cause them to wear and break. The solution was the addition of metal brushes, which are placed at the top and bottom of the armature so that the coil spins between them. The diagram below shows how electricity exits through the top brush to light the bulb that is wired to it, and the circuit is completed with the second wire and the bottom brush. Through this brush system, the electricity is harnessed, and ready to use!

Diagram of an AC generator.
Gibson page 195. 

These types of electricity generating devices are most often used in large scale industrial operations, because they are able to produce a large amount of electricity. This type of generator utilizes the armature as a movable core, which maintains an unvarying voltage and prevents electricity from surging and lights from flickering.

Now, when I walk past the core, I not only know that it is not a piece of modern art, but I am more aware of how it works to produce electricity. I hope that this research is useful to our visitors, who want to know a little bit more about this artifact and how it works.

Tierney Dickinson
Summer Intern
Telluride Historical Museum
Charles R. Gibson, The Romance of Modern Electricity: Describing in non-Technical Language What is Known About Electricity and Many of its Interesting Applications, (Philadelphia: J.B. Lippincott Company , 1906 ) Romance of Modern Electricity&hl=en&sa=X&ei=Cvr_UfnFOpKCyAGHo4HIBg&ved=0CDoQ6AEwAA


  1. A comment from a local metallurgist and engineer: I can see no physical evidence that our artifact was ever designed to rotate -- there's no axle on which it could have been suspended. Furthermore, the steel laminations which are so artfully "exploding" and the deep grooves in the laminations look like the core of an early transformer ... and there is evidence that the "pinheads" at Ames did a lot of early experimentation with transformers in their quest to get electricity boosted in voltage, and lowered in amperage, to transmit the current up the hill to the Gold King. Copper wire, long since stripped off this core, and quite probably reused due to it's relative scarcity and high value back in the late 1800s, would have been wound into the grooves in two separate circuits. The low voltage, high amperage current generated by the water turbine turned generator (with a rotating armature) is fed into one set of windings, and the current induced into the second set of windings, with multiple times more loops, comes out "transformed" to higher voltage and lower amperage (according to the equation that current = voltage x amperage; therefore as current remains constant coming out of the generator, the resulting current sent up the hill at lower amperage is at higher voltage.) The early engineers quickly discovered that controlling and switching high amperage current was problematic and dangerous, and transmission over distances was greatly enhanced by boosting the voltage ... and brought back down at the other end of the line with a twin transformer. I once saw some documents from Westinghouse engineers discussing experiments with transformers at Ames - I don't know where the documents are, but they must be in the Museum's archives - and I've seen historic photos of early transformers which look an awfully lot like our artifact. Remnants of transformer cores can be found at mine and mill sites around the area - some of the most distinct are near the old Western Power building at Tomboy ... and they are quite similar in form: lots of laminated sheets of steel with grooves for the windings. Ours is unique in a couple of ways: it's ovoid shape does mimic early armatures (and I surmise that's because the pinheads had these materials available), and it was probably air-cooled (whereas later, and all large modern transformers are put into an enclosure filled with an insulating cooling fluid ... because passing all the current through the windings produces heat. Your cell phone charger is a small step-down transformer - and you can feel how hot it gets ... imagine how hot the artifact would have gotten!). See for more explanation and some photos of early transformers.