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It's Time To Replace 60 Hz 110V Electricity

Discussion in 'General Electronics' started by Mark Thorson, Aug 16, 2003.

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  1. DarkMatter

    DarkMatter Guest

    The motor and gasses are isolated from each other, dumbshit.
     
  2. DarkMatter

    DarkMatter Guest


    Very carefully.
     
  3. Bill Vajk

    Bill Vajk Guest

  4. I don't think there is any isolation. Sealed compressor units clearly
    don't expect isolation. With the motor on the low side, the outer seal
    of the compressor unit is all that is needed. Capacitor start/run motors
    don't spark. For a DC compressor of similar design, a brushless
    permanent magnet DC motor with its attendent baggage of electronics
    would have to be used. Adding electronics is a reliability issue
    particularly in power handling equipment.

    Chuck
     
  5. daestrom

    daestrom Guest

    Well it's your motor, so you obviously saw it. But many universal motors
    have the field and armature connected directly to the AC line. As the line
    reverses polarity of the field winding, it also reverses in the armature
    winding and the torque continues in the same direction. But the brushes
    spark a lot more than a good DC motor does.

    daestrom
     
  6. daestrom

    daestrom Guest

    DEFINITELY. The heat of sparking brushes would probably break down the
    Freon to the poisonous phosgene gas. And atmosphere contaminants are one of
    the major causes of sparking/burning of commutators/brushes in the first
    place.

    Navy submarines spent a lot of tax dollars researching the causes of poor
    brush life in DC equipment on nuke submarines. Turns out one of the killers
    is atmosphere contaminants such as diesel fumes(emergency diesel-gen), amine
    (CO2 scrubber) and freon (A/C & R). Low humidity is another one. The
    chemistry between brass commutator bar and graphite/clay brushes is really
    quite complex. Throw in about 10-20 amps per square inch of brush face and
    its even worse.

    daestrom
     
  7. ....
    It had a permanent magnet field, which rather surprised me.
     
  8. daestrom

    daestrom Guest

    Well, Fred never said it was a universal motor. I only suggested that it
    might be since it ran on AC and used brushes on a commutator.

    daestrom
     
  9. Bill Vajk

    Bill Vajk Guest

    Never said he did but thanks for clearing it up in
    case anyone is confused.
     
  10. I noticed when opening an old floppy and looking at the electronics
    there was a couple of coils driven by a chip, and a wheel with magnets
    (at least magnetic) rotating just above it.
    In such a system a there are no brushes.
    (perhaps 3 phases electronically generated).
    Do harddisk motors work the same?
    You do NOT want stuff sparking of the brushes in the disk compartment.
    (copper, carbon whatever, the slightest thing would ruin the disk surface,
    resulting in a head crash).

    My first (SCSI) CDROM (at that time very expensive) had a motor with
    brushes, it burned out.
    I have seen high speed centrifuges used to separate pluto^H^H^H^H^H
    stuff, using electronically generated 3 phases.
    So maybe those brush problems can be overcome, but at the expense
    of some losses in the drive electronics likely.
    Someone in sci.electronics.design even designed a walkman with
    3 phase motor on 2 AA batteries, 2 years ago or so?
    mm I have one, AIWA, it sounds horrible, as it drops behind on the phase...
    Solved it by buying a mp3 player ;-)
    The 3 phase walkman is for sale.
    JP
     
  11. Floppies, as far as I know, which used brushless DC motors had a
    commutation sensor consisting of three hall effect devices which
    detected the magnets on the rotor. All modern hard drives I know of use
    brushless DC motors for the spindle but do not use a comutation sensor.
    The motor is started by software that pretends it is a stepper motor.
    There is a back EMF detector. When it detects BEMF, the drive software
    then commutates by timing from the detected BEMF. This save the cost of
    hall sensors which are not very impressive from a reliability point of
    view.
    It is really hard to crash a head when it is actually flying. I have
    blown cigarette smoke at an open drive while it was running and it did
    not crash. Do that with a stopped disk and it will crash. The heads
    can't take off plowing junk.
    A problem with running motors on low voltage is that you have to use low
    torque constant motors so the currents get very high. An example is the
    DVD drives I work with. Spindle start current is over 1 amp but run
    current is more like 100 to 200ma. I also have to use up to an amp in
    the focus and tracking linear voice coil motors because of the low
    voltage.

    Chuck
     
  12. DarkMatter

    DarkMatter Guest

    Hey, dumbfuck... yes you... Billy boy... I said the gasses ARE
    isolated from the motor, and they are.

    The cooling system is a closed loop, and the motor windings are NOT
    in that loop, dipshit.

    You're the asswipe that doesn't matter. I do more in a week to make
    the world a better place than your lame ass will accomplish in your
    entire life.
     
  13. Bill Vajk

    Bill Vajk Guest

    DarkMatter wrote:

    snip

    Yet another jejune post from DarkMatter who doesn't matter.

    You were wrong and continue to be wrong, no matter how
    you fume. Please check your facts before posting nonsense
    to usenet. I gave you a reference URL. Since you ether
    didn't understand it or you have trouble with reading
    and comprehension, drop by the nearest refrigerator
    service shop in your region and discover that the
    most junior apprentice mechanic working there for a
    week knows more about this, and possibly many other
    subjects, than you.

    Now go be a good little boy and take a time out. You've
    become far too excited.
     
  14. In sci.physics, Bill Vajk
    <>
    wrote
    A stepper motor for an air fan?

    My head hurts.

    I could see it working for a heat-pump compressor if
    there's enough force in the motor, but it would take some
    design effort.

    Someone mentioned in another thread the problem of fluid
    friction in a computer disk drive (that's what makes it
    hot) so now I'm wondering how much force a stepper motor
    needs to move the heads. I doubt that it's as much force
    as needed to push a compressor on a 1-ton heat pump,
    though.

    And then there's the electronics needed to drive the thing.
    That's one thing about AC motors; they're really really
    simple. :) At least, from an electronics standpoint.

    Someone mentioned converting AC to DC outside the home.
    That requires diodes, and I've had enough electrical
    problems on my car (having had the generator and battery
    replaced twice, which was a little strange in itself) to
    gently suggest that we'd have problems with such a system.
    At least with our current wiring the transformers might
    blow up but that's about it... :) (From an electronics
    standpoint the transformers aren't too complicated,
    either.)

    This apparently in addition to replacing the commutator
    brushes once or twice a year. Yeah, what a bright idea to
    keep the economy going -- if one's the Motor Brush Man.
    (Does Fuller Brushes do motors? Or just human hair
    grooming equipment?)
     
  15. No, but brushless DC motor fans are very common in computers.
    You really can't get good efficiency with a stepper motor. They also get
    very large for high power.
    The last disk drive to ship using a stepper to move heads in a disk
    drive shipped in 1992. I know about that because I was a servo engineer
    at that company then. The company was Western Digital. Personally, I
    have never designed a stepper head movement system for a disk drive and
    I have done head motion servos in disk drives since 1980. All I ever
    worked on in more than 20 years in disk drives was rotary voice coil
    motors for head positioning with servo position information written on
    the disks.

    Disk drive spindles have been brushless DC motors for many years. I was
    using them in 1980. Brushless DC motors could be used for compressors
    but the power electronics reduces reliability and increases cost. Let's
    not even visit the problem of special magnet materials needed for high
    power applications.
    I can't see any advantage to DC distribution to homes. It does not solve
    any problems and creates some along the way.
    Chuck
     
  16. Bill Vajk

    Bill Vajk Guest

    As lomg as it is contained, no one much cares, but the
    problem is that the result is acid enough to cause
    problems inside the refrgerant loop.
    R134a is a hydrofluorocarbon which, in terms of a greenhouse gas,
    is worse then the freon it replaces.
     
  17. DarkMatter

    DarkMatter Guest


    Are you sure that you know much about chlorinated gases?

    They are quite bad. There is a cloud of it over Antarctica that is
    eating away the ozone layer.
     
  18. Bill Vajk

    Bill Vajk Guest

    Are you sure you understood what I wrote?
     
  19. daestrom

    daestrom Guest

    No Darkmatter, if you're talking about hermetically sealed compressors like
    those used in A/C and refrigerators, you are not correct. The shaft has no
    seals on it at all and the motor windings themselves are cooled by the cool
    low pressure gases as they flow towards the compressor suction.

    daestrom
     
  20. daestrom

    daestrom Guest

    If it's designed well, the heads are always perpendicular to the rotating
    fluid so they have little force trying to push them in or out. Stepper
    motors haven't been used in HD's for quite some time. Servo 'motor's,
    sometimes called voice-coils (because they resemble the coils used to drive
    speakers??) on permanent magnet assemblies seem to be the norm these days.
    Faster and not subject to misalignment issues.
    And don't forget the govt licensing/certification program. And a whole
    committee to legislate standards of brushes ;-)

    daestrom
     
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