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just call it 2 phase

Discussion in 'Electrical Engineering' started by [email protected], Feb 18, 2009.

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  1. I do remember visiting the Sylmar Pacific Intertie facility. They had
    some pretty large harmonic filter components out there. I don't remember
    if they were there to absorb harmonics generated from the switching or
    whether they compensated for reactive currents as well. I also do not
    remember how many pulses they used to approximate a sine wave from the
    switching banks.

    Bill[/QUOTE]


    Wow... you visited their rectification hall? It is immense. I'll bet
    that was a cool field trip (I had to call it that)!
     
  2. Don Kelly

    Don Kelly Guest

    You are showing my age!! Any Heathkits I built had tube sockets (small
    and large). They also had big heavy transformers and nasty voltages.
    They did give a good product for a decent price and some ability to read
    and follow instructions (and solder properly-). A good way to get a
    decent radio and audio amp as well as basic test equipment at a decent
    price. Sure their scopes weren't up to Tectronics but in many
    applications that didn't matter when budgets had to be stretched.
     
  3. Don Kelly

    Don Kelly Guest

    I do remember visiting the Sylmar Pacific Intertie facility. They had
    some pretty large harmonic filter components out there. I don't remember
    if they were there to absorb harmonics generated from the switching or
    whether they compensated for reactive currents as well. I also do not
    remember how many pulses they used to approximate a sine wave from the
    switching banks.

    Bill
    [/QUOTE]
    Basically harmonic compensation and the scheme would be roughly
    equivalent to a 6 phase supply (12 pulse- often with a star primary and
    delta and star secondaries feeding converters in series).Reactive would
    be drawn from the systems at each end and would depend on the control
    scheme used and the real power loading. Note that filtering will
    generally be on both the AC and DC sides.
     
  4. Don Kelly

    Don Kelly Guest

    As I recall, the pole face windings in series with the interpoles were
    used to counter the distortion of the field flux by the armature mmf.
    The armature mmf tends to weaken flux on one side of the field pole and
    increase it on the other side but some saturation can occur resulting in
    a weakening of the total flux. It happens in all machines but generally
    it isn't all that important in most cases. In the size of machine that
    you mention, it could be of concern. This machine would have been near
    the upper limit for conventional DC machines.
     
  5. That brings back memories.
    The last electronics shop in Tottemham Court Road was Proops,
    which probably went around 20 years ago. Those electronics
    shops all got replaced with PC shops, and now gadget shops.
    Same thing happened in Edgeware Road, except I think Henry's
    is still there (not been there for a long time though).
     
  6. Don Kelly

    Don Kelly Guest

    Yes -you have it right. The interpoles cancel the effect of the armature
    reaction only at the segments under commutation - eliminating the need
    to shift brushes. They also insure that the net induced voltage in the
    coil under commutation is 0. However they have no effect under the field
    poles as they act only in a narrow region on the the neutral axis. The
    distortion under the field poles really wouldn't matter except for
    saturation which causes the increase in flux on one side of the pole to
    be less than the decrease under the other side. The result is a
    weakening of flux under load. This can be partially countered by
    increasing the field current but,for high armature current or highly
    variable loads, this distortion has an effect on commutation- tending
    to increase arcing between segments of the commutator. Interpoles
    alone don't completely handle this problem. Hence the "compensating
    winding"- an attempt to cancel out armature reaction mmf.
    In most machines it is not needed but there are cases where it is very
    useful and worth the expense.
     
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