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From: Patent Tactics, George Brock-Nannestad Shiffy wrote > Prior to WWII Lionel made toy train transformers specifically designated for > 25 Hz operation: whatever windings they used for 60 were not applicable to 25. ----- the lower the frequency the more laminated iron you need to put into your transformer. A lot of 110 V equipment from the US with barely sufficient transformers were connected to the European grid at 220 V by means of transformer, but they broke down, because the transformer could not handle the lower induction at 50Hz. So at 25 Hz that must have been terrible. Italian electric railroads used 14 Hz, because the motors used switches that could function at that "high" frequency. Aircraft use 400 Hz and comparatively little iron. Modern power supplies use 30kHz and higher, and the price of the ferrite needed is more than offset by the minute amounts required. As to length of AC power lines: the grid going from the north of Sweden to the South of Denmark once got into wild oscillations - a huge standing wave. We, too, and the Russians, use AC-DC conversion at convenient points. Best regards, and looking forward to seeing lots of you in Cleveland, George