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Re: T unified appliance theory

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  • jur@xxxxxxx.xxx
    ... The 400Hz electrical power components--motors, generators, and the like--are the children of the aircraft industry. Looking for lighweight ways of getting
    Message 1 of 55 , May 3, 1999
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      coexusa wrote:
      > Also, are there other problems associated with a 400 cycle
      > appliance? Are there health issues? Are there emission (EMF or RFI)
      > problems? I would love to hear from the electrical gurus out there.

      The 400Hz electrical power components--motors, generators, and the
      like--are the children of the aircraft industry. Looking for lighweight
      ways of getting electrical power onboard aircraft shortly before WWII,
      it was decided to go for the 400Hz standard. There was less iron
      required and thus the size and weight was reduced.

      How many remember thw war surplus Dynamometers that were available in
      the 1950's? These little puppies were basically an integrated motor
      generator on the same shaft used to provide the DC necessary (before the
      days of efficient diodes) for aircraft radios and avionics. And again
      they were 400Hz.

      As far as EMI and health hazards and the like, 400Hz is pretty benign.
      In fact the UL and the ARRL charts show EMI and health risks lower than
      with 60Hz. Bsides it's easier and lighter to build a reactive filter to
      block out the 400Hz from your sensitive aircraft electronics.

      Designing rotating machinery for 400Hz was quite an advancement in its
      day. The only thing comparable were the rotating high frequency
      generators that were used for some of the low band radio tranmitters
      during that era. The low frequencies of 25, 50, and 60 Hz were
      comprimises on the state of technology of bearings, dynamic balancing,
      air gap design, and designing armatures that wouldn't fly apart. (If
      you ever saw a machine's flywheel break apart at high speed, you'd know
      what I mean.)

      However, because of the heat transfer characteristics of aircraft
      rotating electrical machinery, they'd make poor substitutes for
      earth-bound equipment. You'd essentially have to used forced air or
      refrigerated cooling to make them operate efficiently or make them
      capable of operating any where near their nameplate rating.

      It's interesting to note that the electric automobile experimenter and
      DIY buider of the 1970's, Baylor, used surplus 400Hz aircraft generators
      reconfigured as motors for his creations. This was largely because they
      were cheap and plentiful at the time.

      Frank Jur
    • coexusa
      Dear Wallace: Thank you for your detailed response. I appreciate your honest answer regarding the safety of fuel cells. What I learned from your post is the
      Message 55 of 55 , May 16, 1999
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        Dear Wallace:

        Thank you for your detailed response. I appreciate your honest answer regarding the "safety" of fuel cells. What I learned from your post is the different temperatures that various fuel cell technologies run at. 1,000 degrees!! Wow, that is hot. They will have to do some serious protecting and shielding on those. I guess we will all have to keep watching the progress of the various technologies, wait and see which ones come out on top and then read about how "safe" they are. As with everything in this country, there are going to be pro and con forces and safety will undoubtedly be brought up during the debate. News at 11:00. GRIN...

        Dye Hawley

        Dear Dye, The straight answer is that I don't know anything about the safety of fuel cells. I have no personal experience with working with them. But I can make some reasonable assumptions, and comparisons.
        First, the PEMFC. While in operation, it has some free hydrogen in one side of the membrane in each cell, and on the other side there is air. How great a volume of hydrogen is there I don't know but from the drawings I have seen of such cells there doesn't appear to be very much. Some automotive fuel cells have a tank of hydrogen. This is likely under high pressure otherwise the volume it can carry is very small. Even under high pressure its capacity won't get you the two or three hundred miles you expect from a tank of fuel. It is unlikely that such cells will go into production. Other cells have tanks of gasoline just like the one currently in your car. These have known dangers. Still other cells use methanol as fuel. I should imagine these are as dangerous as a tank of Korean whiskey. If you drink it you may die or go blind. I remember, in 1952, seeing a big signboard in Seoul listing the number dead and the number blind that week from drinking Korean whiskey. A tank of propane may fuel the cell. I recently posted an account of an accident that incinerated a lawyer in Louisiana that used to appear against me in many cases in which I represented small non-profit electric utilities and he represented big electric utlity monopolies. He and his wife ran into the back end of a pickup trunk on the Lake Ponchartrain causeway. The truck was parked with its lights out. It was powered with a tank of propane. Finally, stationary PEMFC fuel cells are powered by a methane gas pipe. This carries, I suppose, the same danger as the gas hot water heater in your cellar or your gas drier or a gas stove or gas furnace. Its safety is aptly but subtly compared with electric appliances in the advertising campaigns of electric utilities which advertise "flameless electric heat" The PEMFC operates at 100 degrees Centigrade which is about the temperature of the water in your car radiator. If you were in an accident, perhaps a few drops of this water would get on you, not as much as the two or threegallons of hot water in your present car radiator. The fuel cell doesn't need the water to operate and probably discards it a few drops at a time on the road as it is generated in the fuel cell.

        The molten carbonate and solid oxide fuel cells would have the same hazards as to their fuel supply but they operate at significantly higher temperatures. I don't know that anyone has designed a MCFC or a SOFC for a transportation application. If you were in a crash there are the higher temperatures to deal with. The MCFC operates at 500 or 600 degrees Centigrade. I don't know whether this temperature is lower or higher than the temperature of your exhaust manifold in your present car. The SOFC at 1000 degrees Centrigade. Now that is a high temperature.If these are in your cellar and are not properly shielded, they would offer the prospect of some rather bad burns, a fire hazard for your house if not properly sealed off from flammable materials. However if your cellar has a cement slab and concrete block walls, you could probably put up a concrete block partition to seal it off. But it is unlikely that one of these would be in your cellar because these come in sizes too probably too large for a residence unless you live in Buckingham Palace or the White House. They might be used for a large office building or apartment house. They would go in the cellar along with the high pressure boilers that are down there now and require licensed engineers to operate them. Also, they might be located at existing substations that are now fenced off from the public. If someone climbed the fence there would likely be more danger from touching the high voltage or even low voltage bus. This is even more likely if one picks the lock on the gate and drives in with a whip antenna which can draw some nice arcs with the right contact in a distribution substation.

        I started with the proposition that I have no personal knowledge of the safety of fuel cells. But common sense would suggest that they are less dangerous than current technology and far less dangerous to your health in confined places where you breath their output as compared with a diessel or gasoline powered generator. Wallace Edward Brand

        coexusa wrote:

        Dear Wallace: With all due respect... you keep answering my questions about fuel cell safety with "comparisons" to internal combustion engines and gasoline!! Stop lawyering!! I am NOT stupid. I know the risks and dangers of gasoline, etc, etc. I am only trying to learn more about the dangers (if any) of fuel cells and hydrogen as it is used in a fuel cell. You keep defending fuel cells like I am some anti-fuel cell person! Well, I am NOT anti-fuel cells. I am just trying to learn more about them...so, you can stop comparing them to gasoline and internal combustion engines and PLEASE answer my question about the dangers or just say, "I don't know?". I am just as excited about the possibilities of fuel cells as you are, but I think that we should ALL look at the risks of them being involved in automobile accidents, etc. That is all I am trying to ascertain. Thanks, Dye Hawley

        In your internal combustion engine there is a cup full of gasoline in your carburetor right next to that hot engine. If your needle valve gets dirty, that gasoline will spill over on your hot exhaust manifold and, guess what --- it will catch on fire. If you have an electric fuel pump, the gasoline will keep pumping out from the tank to the engine compartment and there goes your car and maybe you too.. Wallace
        coexusa wrote:

        From: "coexusa" <coexusa@...>
        Dear Fred:

        Right ... and Wallace pointed out to me that there is no "fuel tank" of
        hydrogen but there is a certain amount contained within the fuel cell. I
        just have not been able to find much discussion about the potential dangers
        of this? Hey, don't get me wrong... I understand how dangerous gasoline is
        (flashpoint, etc) but I am pretty ignorant on the comparisons between
        gasoline (a liquid) and hydrogen (a gas). I would love to see a
        side-by-side comparison chart.


        Dye Hawley

        >From: "Fred W. Bach" <music@...>
        >coexusa wrote:
        >> From: "coexusa" <coexusa@...>
        >> Dear Michael:
        >> Hear, Hear. I certainly agree with you on complimenting Wallace for his
        >> enthusiastic efforts to promote fuel cells. I am still wondering about
        >> safety of hydrogen in a fuel tank on an automobile? Hydrogen is a gas
        >> even though it dissapates very quickly, if two automobiles get into an
        >> accident, and a spark happens, I think that there would be one heck of an
        >> explosion. Comments anyone? Has anyone proven that Hydrogen is safer
        >> gasoline? Remember, you are comparing a liquid with a gas. Big
        >> Dye Hawley
        > I saw this done for real on TV. A lot depends on how the hydrogen is
        > stored. But in any case the hydrogen gas and the resultant explosion
        > tended to go straight up with residual fire minimized, in stark contrast
        > to the collision between gasoline-powered cars where the flame tended
        > to spread out and get all over everything as the gas soaked the car and
        > all passengers. Hydrogen appeared to be safer than gasoline.
        > .. Fred Bach music@... Opinions are my own.
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