3-phase power; was: cctalk Digest, Vol 88, Issue 2

On 1/4/22 4:04 PM, Grant Taylor via cctalk wrote: 400Hz of course, could be encountered if one shopped war-surplus airborne electronics. I still remember adventures on Chicago's S. Michigan "Surplus Row". Word was that the original plant acquired a generator from a bankrupt carnival operator in the 1910's. But it was used all over the place; my job was with the pyrometer (instrumentation) department. It was incredible seeing the lengths that were taken to avoid using 60Hz power for things like a chart recorder. It was explained that the 25Hz power was generated on-site from coke oven gas and so was essentially free, while the 60Hz was purchased from the local utility. DC, of course, was used for overhead cranes and welding. Every shop had outlets with yellow labels indicating the voltage and frequency. You could plug a coffeepot or hot plate into the 110V (not 120 or 115 or 117) 25Hz outlet, but beware of using it for much of anything else, save lighting. BTW, you have seen no more irritating lighting than mercury-vapor lamps running off of 25Hz. Even in our shop, which used 220V 25Hz incandescent lighting, you could see the pulsation. I did discover that you could take a 110V 25Hz induction motor fan and plug it into 230V 60Hz for a real kick in performance...and probably shorter bearing life. 440V/460V 3-phase in both frequencies were in most shops. Said plant has long since vanished. This was the day of blast furnaces, open hearth furnaces and all the stuff that it fed, like merchant mills, hot- and cold-rolled sheet, tinplate, galvanized...all from a bunch of rocks. --Chuck