Back in the 70's when I was still a junior electrical design engineer working for a distribution transformer company, we used algorithms loaded into TI calculators to compute the electrical, heat, and mechanical stresses. I later got the task of modernizing those codes and merging them with a FORTRAN code that another engineer had written and abandoned because it was too expensive to run. Things went well at first, we saved a lot of time and used that as any good engineer would to optimize our designs using different parameters to reduce cost and improve efficiency, both very important to my company and its customers. Then one day we got a limiting case which we didn't recognize at the time. As usual, one of our engineering assistants used the computer generated design and the old methods to validate the design. The engineer always takes responsibility for the design. After the build, the unit, a 3 phase unit that had 76,000 volt inputs, was tested in our "hi pot" chamber - a voltage pulse of the rated voltage but with reduced current and only for a short pulse. The center core winding turned into shards of copper spaghetti in the 8 foot tall tank. It cost $25,000 to repair, and delayed delivery for 3 weeks. My heart rate hit about 200 when the engineering manager called me and my supervisor into his office. Then he explained that he had run the calculations also, and discovered that our methods had a flaw in the prediction of the axial forces on the center coil. It was a very subtle mistake, and he said it could have been much worse. We were able to revise the code within a few hours, and that incident led to further improvements in methods and automation. It also taught me my most important lesson about computers - human error is the greatest risk. Real tests of your code sometimes do "blow up".
