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| Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) (661178) | |
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| (664350) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by JournalSquare-K-Car on Sun Aug 10 12:54:53 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by Chris R16/R2730 on Sun Aug 10 12:30:39 2008. So it would work? And it wouldn't take much to make a SMEE, or even an NTT to run on AC. SMEE DC motors can be configured in series, to run on AC like GG1 motors, and the NTTs can be fitted with rectifiers. Though it would add a level of BS to the equation, the SMEE cars are more versatile in this case. |
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| (664359) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by JournalSquare-K-Car on Sun Aug 10 13:10:52 2008, in response to Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by JournalSquare-K-Car on Sun Aug 10 12:06:09 2008. Actually, now that i recall, the signalling with an AC powered system is a bit mor complicated, correct? But how much more complicated, if this is indeed the case?I know AC systems need impedance bonds to allow propulsion current to pass, and to keep signals within a certain area. I asked about these devices a while ago, but that is their general idea. |
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| (664368) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by trainsarefun on Sun Aug 10 13:24:04 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by Chris R16/R2730 on Sun Aug 10 12:30:39 2008. Given some of the new tunnels that would be required, billions indeed. |
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iPhone 6 (4.7 Inch) Premium PU Leather Wallet Case - Red w/ Floral Interior - by Notch-It |
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| (664371) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by Chris R16/R2730 on Sun Aug 10 13:27:16 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by trainsarefun on Sun Aug 10 13:24:04 2008. AC doesn't need to be delivered overhead. |
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| (664381) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by trainsarefun on Sun Aug 10 13:40:55 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by Chris R16/R2730 on Sun Aug 10 13:27:16 2008. Not necessarily, as wall sockets attest, but overhead wire is certainly the favored method. |
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| (664395) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by JournalSquare-K-Car on Sun Aug 10 13:52:05 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by trainsarefun on Sun Aug 10 13:40:55 2008. Why not use the third rail? |
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| (664421) | |
Re: What is the mechanical condition of the Low V? |
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Posted by Hank Eisenstein on Sun Aug 10 14:26:32 2008, in response to Re: What is the mechanical condition of the Low V?, posted by irt1958 on Sun Aug 10 12:18:23 2008. That is an awsome sight. Nothing like opening a high-voltage switch to get your juices flowing right down your leg. |
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| (664426) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by Hank Eisenstein on Sun Aug 10 14:29:44 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by JournalSquare-K-Car on Sun Aug 10 12:54:53 2008. There are a number of hurdles to this, including the required multi-day full-system shutdown to change the propulsion system in all the cars. |
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| (664432) | |
WMATA? Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by trainsarefun on Sun Aug 10 14:42:01 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by Hank Eisenstein on Sun Aug 10 14:29:44 2008. For a system like WMATA, I'm surprised that they didn't do it from the start, considering their straddling the commuter rail and rapid transit elements in their efforts. |
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| (664433) | |
Re: R1/9 acceleration (Re: What is the mechanical condition of the Low V?) |
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Posted by Hank Eisenstein on Sun Aug 10 14:42:33 2008, in response to Re: R1/9 acceleration (Re: What is the mechanical condition of the Low V?), posted by JournalSquare-K-Car on Sun Aug 10 10:41:08 2008. That's heat from friction, which is unavoidable and short duration; as opposed to the frequent stops that a mass transit car will make. Disc brakes are typically vented, and in some implementations drilled, so they dissipate their own heat. And I don't think you have a good enough understanding of eddy currents (or friction) to explain yourself.You are suggesting dissipating the heat from dynamic braking through the wheels. |
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| (664499) | |
Re: R1/9 acceleration (Re: What is the mechanical condition of the Low V?) |
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Posted by JournalSquare-K-Car on Sun Aug 10 17:01:34 2008, in response to Re: R1/9 acceleration (Re: What is the mechanical condition of the Low V?), posted by Hank Eisenstein on Sun Aug 10 14:42:33 2008. Umm, guy, you do realize that R9 railcars didn't have dynamic brakes, and neither did any other mass produced prewar stock...what exactly are YOU saying? |
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| (664514) | |
Re: What is the mechanical condition of the Low V? |
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Posted by JournalSquare-K-Car on Sun Aug 10 17:16:53 2008, in response to Re: What is the mechanical condition of the Low V?, posted by Hank Eisenstein on Sun Aug 10 14:26:32 2008. but i thought an Arc is a closed circuit...it takes up power. |
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| (664515) | |
Re: What is the mechanical condition of the Low V? |
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Posted by JournalSquare-K-Car on Sun Aug 10 17:17:22 2008, in response to Re: What is the mechanical condition of the Low V?, posted by irt1958 on Sun Aug 10 12:18:23 2008. Oops, but since an arc takes power to prodce, isn't it like a closed switch? |
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| (664517) | |
Re: WMATA? Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by JournalSquare-K-Car on Sun Aug 10 17:18:59 2008, in response to WMATA? Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by trainsarefun on Sun Aug 10 14:42:01 2008. True, maybe there is a reason though... |
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Re: What is the mechanical condition of the Low V? |
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Posted by irt1958 on Sun Aug 10 19:25:56 2008, in response to Re: What is the mechanical condition of the Low V?, posted by JournalSquare-K-Car on Sun Aug 10 17:17:22 2008. Excuse me, I was thinking of an arc being *caused* by an opening circuit (filament failing). The original scenario stated the the full *force* of 600 volts is applied not dropped. With the street railway bulbs, as I understand it, the arc is stretched out or supressed by the vacuum, and disappated; effectively cutting off the runaway current. This will leave a 600v DC potential, at the break, *after* the arc dissipates (if one actual forms) because 0 current flows at this point.. That was my point. The answer to your question is yes. (It's been awhile -I've been working on digital circuits too long lol) |
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| (664657) | |
Re: What is the mechanical condition of the Low V? |
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Posted by irt1958 on Sun Aug 10 19:29:18 2008, in response to Re: What is the mechanical condition of the Low V?, posted by Hank Eisenstein on Sun Aug 10 14:26:32 2008. lol Yeah down the leg and out several bodily orifices. |
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| (664661) | |
Re: What is the mechanical condition of the Low V? |
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Posted by SelkirkTMO on Sun Aug 10 19:32:26 2008, in response to Re: What is the mechanical condition of the Low V?, posted by Hank Eisenstein on Sun Aug 10 14:26:32 2008. Feh ... if you REALLY wanna see some excitement, there's nothing like a magnablaster contactor opening up on a klystron cabinet feeder. Now THERE'S a light show with surround sound! :) |
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| (664683) | |
Re: What is the mechanical condition of the Low V? |
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Posted by JournalSquare-K-Car on Sun Aug 10 19:56:55 2008, in response to Re: What is the mechanical condition of the Low V?, posted by irt1958 on Sun Aug 10 19:25:56 2008. I see, thanks.Digital circuits...BS!!! I like the older stuff myself. Digital seems to do everything for you...If anything, can't you use vacuum tubes instead?? :D |
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| (664707) | |
Re: What is the mechanical condition of the Low V? |
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Posted by Hank Eisenstein on Sun Aug 10 20:25:54 2008, in response to Re: What is the mechanical condition of the Low V?, posted by JournalSquare-K-Car on Sun Aug 10 19:56:55 2008. I hope to all that is holy you are joking about vaccuum tubes. |
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| (664713) | |
Re: What is the mechanical condition of the Low V? |
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Posted by JournalSquare-K-Car on Sun Aug 10 20:31:40 2008, in response to Re: What is the mechanical condition of the Low V?, posted by Hank Eisenstein on Sun Aug 10 20:25:54 2008. Why? In the old days, they did everything with Vacuum tubes. I am not saying they are good for everything. but they ARE more robust than chips. For example, radio stations still use tubes to broadcast, don't they?For smaller things, ships are good, but lately, the quality of the hardware has been falling. The chips made nowdays are very fragile, and they screw up data easily, they are too small, and their properties deteriorate. |
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| (664731) | |
Re: What is the mechanical condition of the Low V? |
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Posted by SelkirkTMO on Sun Aug 10 20:53:00 2008, in response to Re: What is the mechanical condition of the Low V?, posted by Hank Eisenstein on Sun Aug 10 20:25:54 2008. Maybe he's onto something and has discovered the "permafilament" which never opens and the cathode sleeve that never shorts. :) |
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| (664738) | |
Re: What is the mechanical condition of the Low V? |
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Posted by JournalSquare-K-Car on Sun Aug 10 21:03:58 2008, in response to Re: What is the mechanical condition of the Low V?, posted by SelkirkTMO on Sun Aug 10 20:53:00 2008. Well, i get your joke...except about the cathode sleeve shorting...BUT solid state stuff fails too. Didn't you say you had a TV from 1969 that works? Old radios still work, and the like. Newer ones crap out more often, and new computers are total BS, hardware wise.But a permafilament would solve the biggest problem of vacuum tubes, which is their tendancy to burn out. There MUST be a better way. There are materials like crystals which display rectifier properties...Seriously, Vacuum tubes are essentially rectifiers, in the case of radio transmissions, aren't they? In the case of computers, they are a bit different. Each Vacuum tube is like a transistor, i think, with on/off states. |
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| (664827) | |
Re: What is the mechanical condition of the Low V? |
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Posted by SelkirkTMO on Sun Aug 10 22:32:39 2008, in response to Re: What is the mechanical condition of the Low V?, posted by JournalSquare-K-Car on Sun Aug 10 21:03:58 2008. Expansion and contraction of the filament over many cycles will cause the coatings to wear off and eventually you end up with a heater/cathods short. Sometimes, doesn't matter if both the cathode and one side of the filament are at ground, but most of the time you'll get hum or humbars in video or worse, the short will cause the filament to go "pop" ... all depends on the cathode resistance and how the filament is wired up.Vacuum tubes generally don't do high frequencies well, have rather non-linear conductance curves, have wide variances in the same type tube owing to small differences in internal dimensions, and of course die. And from the first time you light one up, the emission from the cathode material goes down hill from there until they eventually don't conduct any more at all. There's good points to all technology and tubes are useful for some things (for example, an electromagnetic pulse is far less likely to trash a tube circuit than solid state) but really awful for others. And like semiconductors, tubes will normally pass DC in one direction only ... but the minute you light up a tube circuit, from that moment on, it's only a matter of time before it dies or fades away. :) |
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| (664834) | |
Re: What is the mechanical condition of the Low V? |
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Posted by RonInBayside on Sun Aug 10 22:48:52 2008, in response to Re: What is the mechanical condition of the Low V?, posted by RIPTA42HopeTunnel on Tue Aug 5 07:57:35 2008. "or vinyl replacement windows on a historic home"I've done that. It isn't historical restoration, but it protects the home nonetheless and it sure cuts your climate control bill! |
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| (664842) | |
Re: What is the mechanical condition of the Low V? |
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Posted by JournalSquare-K-Car on Sun Aug 10 23:06:39 2008, in response to Re: What is the mechanical condition of the Low V?, posted by SelkirkTMO on Sun Aug 10 22:32:39 2008. I see...So you are saying that after a while, the filament will no longer boil off electrons? I thought it has to break in order for it to stop conduction in one direction. Anyways, this is a cool site Supposedly what that guy made is not only a rectifier, but a transistor as well. Interesting. So can all rectifiers be used as transistors to create radio frequencies in the diagrams of his? |
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| (664849) | |
Re: What is the mechanical condition of the Low V? |
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Posted by SelkirkTMO on Sun Aug 10 23:13:51 2008, in response to Re: What is the mechanical condition of the Low V?, posted by JournalSquare-K-Car on Sun Aug 10 23:06:39 2008. Cathodes are covered with a coating which is the actual emitter of electrons as a plain filament doesn't do as well as enhanced coatings on the cathod cylinder. Eventually though the surface cooks off and emission drops off ... every time an electron leaves, the metal dies a bit.And yeah, dissimilar metals can make for diode junctions ... some options are better than others. All a matter of what the "front to back resistance ratio" works out to be ... |
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Re: What is the mechanical condition of the Low V? |
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Posted by Jeff H. on Mon Aug 11 03:10:32 2008, in response to Re: What is the mechanical condition of the Low V?, posted by irt1958 on Sun Aug 10 19:25:56 2008. An arc, once started, will continue until the externallyapplied voltage is no longer enough to equal the voltage drop across the arc. However, unlike a resistor, the V-I curve is highly non-linear, and of course varies with the length of the arc. |
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| (664948) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by Jeff H. on Mon Aug 11 03:20:37 2008, in response to Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by JournalSquare-K-Car on Sun Aug 10 12:06:09 2008. We've only been through this a hundred times before on this board.There is no engineering advantage to using low-voltage (600-1000) volts AC on the third rail. The slight efficiency gain from using multi-tap transformers instead of resistors to accelerate the train (remember, the resistors are only in the circuit for a short period of time....the bulk of the energy consumed by the motors happens in full series or full parallel) would be more than lost by the lower inherent efficiency of single-phase AC commutator motors (that's what the GG1 used). Also, because of skin effect, the transmission losses on the low-voltage side would be higher. The reason single-phase AC was used at all was that it was coupled with high-voltage catenary distribution. All this is quite moot, since all modern transit equipment is using 3-phase induction motors with solid-state inverter drive, which is much more efficient. |
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| (665008) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by JournalSquare-K-Car on Mon Aug 11 09:42:27 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by Jeff H. on Mon Aug 11 03:20:37 2008. I see, thanks.But what was wrong with GG-1 motors? I see that the AC current would heat the motor a bit more due to eddy currents..but all motors, AC, and DC produce eddy currents. And besides, if it is a problem of running motors on AC, you can rectify it, but then I guess the gains would be questionable. |
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Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by RonInBayside on Mon Aug 11 11:00:28 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by Jeff H. on Mon Aug 11 03:20:37 2008. What does the MBTA Blue Line use north of the airport, voltage and feed-wise? |
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| (665137) | |
Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration) |
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Posted by Dan Lawrence on Mon Aug 11 12:52:42 2008, in response to Re: Why isn't Alternating Currentu used to power Subways? (was R1/9 acceleration), posted by RonInBayside on Mon Aug 11 11:00:28 2008. 600 volts DC. Same at the third rail. |
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