Re; Posting of RODALCO in reference to 400hz motors & transformers.
Rebuttle. In the early development of electrification/electric traction of the Pennsylvania Railroad circa 1895-1968. That railroad in its hey day solved a lot of problems with an engineering co. Gibbs & Hill co. . There wher very unique problems at the beginning of electrification because no one else tested it other that small street railway companies with limited budgets. One big problem was the limited space locomotives had near the driving wheels. Yes I've seen and been under the belly of a GG-1 locomotive at the museum in Stausberg PA.It was interested to see twin/tandem 350HP traction motors hung through like a wheel barrow suspension. Tight fit. Those series commutator motors, I thought of compairing the size with a 100 HP 3 phase 60hz induction motor where I work.Those motors on the GG1 where not that much larger than the 60Hz 3 phase induction motor.
Now lets visit a book "Electric Traction on the Pennsylvania Railroad 1895-1968 by Michael Bezilla Through the Pennsylvania State University press, Chapter 3 [Alternating Current at Philadelphia] Page67 Stated as;
*******"American railway electrifications using alternating current had now standardized on 25 cycles. The lower the frequency, the smaller the series-commutator motor could be for a given horsepower output;that is, a motor of a particular size and weight operating at 25cycles had a higher horsepower rating than an identical one operating at 60 cycles. As the frequency increased, so did the dimesions of the motor, in order to maintain a specified horsepower. This relationship was of little importance for home or factory use. For railroads, it was vital. An electric locomotive had to pack as powerful motor as possible into a very restrictive space. In addition, railways using low-voltage d.c. sytems but relying on an a.c. generating and distribution system found that the lower the frequency of the alternating current, the more efficiently it could be converted to direct current."***************************
To conclude my findings on the matter, since I've never worked on aircraft wiring or on aircraft electric motors and equipment, I cannot visualize high horsepower slow RPM motors at 400hz. I would have to assume they are high RPM motors of the fractional HP type. I know a transformer at that frequency would have much less iron laminate. As a licensed Radio Amateur, I've built old style tube amplifiers associated operating transmitters. There are some coupling circuits that are used like isolating transformers except they do not have any iron laminated cores. So a 25 cycle transformer may be much larger and heavier than a 60hz counterpart of the same KVA ratings, but correct me in spite of what I have researched and seen, I may be wrong. Don't forget these locomotive motors where somewhat lower speed than the norm.They where also geared seperatly for passenger and freight. I have the complete shop manuals of the GG-1 series locomotives.
What I have found is that electric motor applications, wheather it be electric railways, Ships, Aircraft or industrial establishments, they are not all the same. They all have their unique niche.
Finally on those pictures of a three phase locomotive, don't forget the old Railroad tunnel under the Cascade Mountains in Washington State had a 3 Phase corner grounded delta system at 25hz @6,600volts. The locomotives had two old style street car trolley poles [wheel type], one for each of the phases, with extra insulators on the retreaver cord to disconnect the locomotive from the overhead. Heck, I think I would rather use a High voltage hookstick and rubber gloves just to be on the safe side, along with an arc blast suit.
I hope someone may agree with me.
Paula Walach-Industrial Electrician
