figure 1. A 15 million-V bolt of lightning leaps between two impulse generators in GE's High Voltage Laboratory in this image from 1949 (photo courtesy of The Berkshire Eagle, Pittsfield, Massachusetts). were sometimes referred to as "lightning machines." In a 1969 article in the publication Popular Science, they were even called "thunderbolt machines." there were two large impulse generators in the high Bay, which were visually impressive, being composed of alternating black and aluminum sections. these machines had been constructed in 1949 using some new parts and some parts that had been kept in storage for nearly a decade because they had been used to build somewhat smaller impulse generators for the Ge exhibit at the 1939 World's Fair in new york city. At the fair, visitors were treated to an artificial lightning discharge of 10 million v over a distance of 30 ft (9.1 m). In later years, a similar demonstration was featured as part of open house events at the Pittsfield Ge plant for employees' families and friends. Since the generators in Building 9 were larger than those at the 1939 From Imagination... to Real-time Leading developer of open real-time digital simulators and hardware-in-the-loop testing equipment for electrical, electro-mechanical and power electronic systems www.opal-rt.com may/june 2014 ieee power & energy magazine 111http://www.opal-rt.com