TINY SPOOL CONQUERS ARC

CD 2487099 E&MP15.018

Electric Circuits, Breakers

1936

Chemist E. Venable demonstrates how a copper-wound spool puts out an electric arc to protect electrical transformers against their own failure.

The spool, coated with zinc oxide, is shown near the top of the left tube, just above the level of the liquid inerteen.

Near the bottom of the tube an electric arc is seen jumping between two closely fitted electrodes.

The arc releases hydrochloric acid fumes from the inerteen, these fumes react upon the zinc oxide coating on the spool, forming an electric circuit and operating a relay which turns on the red signal light under Venable's right hand.

Installed in a steel-clad transformer, the spool just as easily disconnects troubled transformers from the power line when a short circuit occurs. 

Original Caption by Science Service
^©Westinghouse