The NYCentral railroad was considering electrifying in the 70's. The utility I was working with was laying out 60hz and estimating costs for substations to support this project. As it was explained to me...diesel train engines powered generators which powered DC traction motors. Electric trains would replace the diesel engine/generators with inverters. I'm not sure of the details but the electrification of the NYCentral did not take place while I lived in NY State. It would appear that light rail electric trains (commuter trains) were more economically feasible. We have many electric light rail lines in operation in this country. Full scale trains (freight trains and Amtrack passenger) are still diesel powered here in the States...at least all that I am aware off. Perhaps as unit coal trains fade off into history this may change. These are perhaps the heaviest example of freight trains as they use quite a few diesel engines to move coal long distances.
Actually both were equally important. Our professional experience is similar. Worked in utility and telecom 40 years. Built many of a Data Centers and couple were DOD. In the old days gone by and antiquated of the 80/90/early 200X's data and voice communications, even though digital in nature, used ground referenced Single-Ended Signaling formats where ground or a voltage reference is used as a circuit conductor. Protocols like: RS-232 PS-2 RCA Jacks TRS Phone Patch TTL ECL CMOS PCI VGA SCSI ATA Any of the Single-Ended Signaling are prone to noise (Common Mode), and radiate signals which can be detected from far. Today that is mostly long gone and replaced with Differential Signaling if copper is used, or fiber optic transmission which doe snot radiate, nor can be tapped or detected remotely. As for shielding essentially everything is double shielded. The Building Envelope is a Faraday Shield with copper mesh encapsulating the building to prevent signals from radiating outside. That of coarse was followed up by the equipment cabinets being fully enclosed and bonded to the Raised Floor Equipment Ground System. Some went to extremes like the raised floor being constructed from Diamond Steel Plate used to form a Equipotential Ground Plane. Under the raised floor was used as a wiring raceway and Plenum. All circuits including power are ran under the raised floor inside metallic raceways. Made a ton of money building data centers for Telecom, Banks, and DOD. Some of those building had up to 120,000/ft2 floor space.
This thread has been interesting reading, reminds me of wye and delta networks when studying for my PE license. Yep, that neutral wire should not carry load for a properly balanced system. Going back to 1970s my first practical experience of balanced systems was living in a old house supplied with 220V (two hot wires and a neutral) where each wire was strung in parallel from another building. The connection of the neutral wire was flaky so sometimes when I turn on a light or use a vacuum cleaner, other lights either become very bright or dim. Or vacuum cleaner runs really slow or fast. I couldn't figure out what was going on, I was taking my first electronics courses so I figured it couldn't be caused by witches or goblins. I noticed the three power wires and the clamps for wiring into the house didn't look great (very old and almost falling apart). I shutoff electricity to these lines to install better clamps and saw the clamp for neutral wire was intermittent. Ha! now I saw why house wiring needs balance between the two hots to minimize load on the neutral, but the neutral probably not completely load free. But with neutral connected not connected to a ground and circuit breaker panel, then that "neutral" wire in the house can be anything. Of course this is not exactly the same as 3-phase lines for power distribution. Regarding three-phase power, 15 years ago I bought on ebay an aircraft coffee maker. It works, it came with the green tag and N-number of 727 it came from (was an ATA aircraft, shortly after getting coffee maker I read ATA got into big trouble with the SEC). But it is 120VAC three-phase 400 hz! So far it has been in a cabinet. It would be impressive for parties, it is well built with teflon wiring, swage fittings, locknuts, safety wire on bolts, etc. This baby can definitely work even when pulling high Gs, except negative Gs as the top is not liquid tight and coffee could spill out.
The "high" leg comes from an open delta wiring scheme where there are only two transformers used to generate 3 phase power. It winds up being a 120/240 3ph with high leg. You can recognize it by the transformer config which is one large xfmr and one much smaller xfmr. At all the secondaries, there will be a 3 ph/ 240v system. One xfmr is center tapped creating a neutral. the other, smaller, xfmr supplies the third leg. However, instead if 120v, there will be 208v on one "leg" at the single phase side. Since this side (small xfmr) is 120 degrees apart from the other phases, it now becomes 208v. 3 phases at 240v between them, 2 phases at 120v to ground and one phase at 208v to ground...the high leg. There are certain customers who will request 240 over 208 because of the machinery they use. Use caution in the panels which are fed with an open delta config. I've seen a lot of equipment bite the dust with a wrong connection. Good luck, I hope this helps...Paul W4GVE Bradenton, Florida...
According to (link) https://en.wikipedia.org/wiki/Prodigal_Genius:_The_Life_of_Nikola_Tesla Prodigal Genius: The Life of Nikola Tesla the reason for choosing 60 Hz was because Tesla wanted to use this frequency because it would make it easier to synchronize clocks. He was deeply concerned with vibrations and the frequency of vibrations and even gave lectures on this. I suspect that another reason we were given 60 Hz is because if you consider that the change from 50 to 60 is 20%, imagine the savings in iron, copper, etc., because of the smaller amounts required. Sure. we had the natural resources for an additional 20% material but when you also consider transporting weights of plus 20%, you can see the savings are not only in material weight. Another comment was: "Having some experience with 400hz systems I became very aware of line losses quickly. If you think 60hz losses are bad try playing with 400hz!" I also worked extensively in Avionics. 400 Hz is a popular, if not exclusive, frequency for Avionics if not 24V. The reason 400 Hz is chosen is because space is allotted for avionics equipment in planes and 'choppers and the designers have to provide equipment to fit that space. 400 Hz equipment is smaller and lighter than even 60 Hz equipment, especially the converters up from 24vdc. Thus the rational for 400 Hz. Also, filtering a higher frequency is much easier; capacitors are smaller/lighter, etc. The comments here are very interesting. The Delta-Y arrangements of power transfer systems is something that a lot of hams are not very experienced in and it's interesting and helpful to see these things discussed by people who work with it. I plan to read to the end of the series, with great interest and am thankful for the patience of the contributors.
According to my lecturer in Electrical History, prof. Stig Ekelöf, the choice of 60 Hz by Nikola Tesla was primarily governed by the balance between copper and iron losses in the complete distribution system. The iron common in the late 1800s had a somewhat limited maximum flux density and a larger hysteresis loop, so for a given amount of copper in the windings, 60 Hz made the most out of the available iron. When large-scale electrification came to Europe some years later, the iron had improved, permitting higher induction with about the same amount of copper and constant iron loss factor, which made 50 Hz transformers more economical. It appears that the concept of 3-phase power commonly is misunderstood by western-hemisphere radio amateurs, perhaps because 3-phase is so uncommon in residential areas. In the Nordic countries, we have been blessed by having 3-phase residential power distribution since the 1920s. 73/ Karl-Arne SM0AOM
In the western hemisphere, 3-phase power in residential areas is as common as can be. 3-phase power just not delivered to dwelling units. (Nordic countries aside, perhaps; but single-phase to dwelling units is the same for most of Europe.) In the USA: Multifamily apartment buildings are typically supplied 3-phase power; but only 1 of the 3 phases, at 208/120V, is distributed to each dwelling unit. Same for large swaths of city to residential homes. My home here has 208/120V - 1 phase of 3; where the 3-phases run down the street, with each phase serving groups of homes. In more suburban areas, with overhead distribution, single-phase 120/240V is distributed to the homes via overhead can-type aerial transformers. However, these transformers are supplied via a 3-phase system, typically at 13kV or so.
Indeed! Silicon steel was unheard of in his time. I wonder what he could have accomplished with modern materials!
