More than meets the eye (ugh, sorry)

The other week, while I was happily working on painting a 4ft diameter fiberglass globe destined for the United States Congress (that is serious by the way) A loud noise rang out, echoing off the other building down on Fulton Market Street. I looked out the window to see a number of people looking down the street next to our building, and just as many backpedaling out of the alley at a decent clip. I then noticed a number of people from the warehouse on the corner shouting and waving at me. They we're shouting things like "You're on fire!" and "Hey! Get the hell out of there." They also persisted in pointing above and behind me as if there were something of importance that I was somehow missing. Since I was not at that point on fire, I had difficulty believing them and responded with things like "What?" and "Really?" So we begrudgingly toddled out of a possibly flaming building and exited into the alley to find two cars completely engulfed in nine feet of flame. Soon after the spectacle took effect, tires started exploding left and right, which served to bring us back to reality. The gas ignited, spewing flame out of the ...uhh..gas filling hole? But anyway, I have a much more realistic understanding of how cars burn, than Holloywood ever provided.



Upon speaking with a fellow gawker he informed me that the transformer had blown, raining down fire on to the innocently parked car, which went up apparently like a car that burns quickly and turned the SUV next to it into a nice toxic bonfire. What is in a transformer that rains down as balls of fire I thought. Why do they have to go and explode all the time in the first place?

Well as is the nature of this blog, I found out. Here is the simple definition of a transformer via Wikipedia:

A transformer is a device that transfers electrical energy from one circuit to another by magnetic coupling without requiring relative motion between its parts. It usually comprises two or more coupled windings, and, in most cases, a core to concentrate magnetic flux.

An alternating voltage applied to one winding creates a time-varying magnetic flux in the core, which induces a voltage in the other windings. Varying the relative number of turns between primary and secondary windings determines the ratio of the input and output voltages, thus transforming the voltage by stepping it up or down between circuits.

Amongst the simplest of electrical machines, the transformer is also one of the most efficient,[2] with large units attaining performances in excess of 99.75%.[3] Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge giga VA-rated units used to interconnect portions of national power grids. All operate with the same basic principles and with many similarities in their parts, though a variety of transformer designs exist to perform specialized roles throughout home and industry.

Allright, fair enough, so what the hell produced a huge ball of fire and a loud explosion?

It's actually much simpler than this post justifies. In generating current, transformers build up a tremendous ammount of heat (lost energy) to counteract this, transformers are filled will coolant to keep the temperatures down, older transformers, and many outdoor transformers use mineral or canola oils to keep them cool. At very high temperatures, these can ignite, and turn into big hot balls of grease fire. The explosion is the electrical arc escaping from the confines of the transformer couplings.

It is important to remember that not all explosions are the result of a blown transformer. Some are populations, emotions, or terrorists.