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Synchro Amplifier Help

Discussion in 'Electronic Design' started by Matt, Apr 12, 2006.

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  1. Matt

    Matt Guest


    Unfortunately, I was raised in the digital age and dont have a
    great grasp of Synchros. I am trying to develop a replacement to a
    synchro amplifier that we use for a piece of military equipment. From
    me research I have learned quite a bit about the Synch amps but I still
    have some questions.

    The input is a resolver 6V 60Hz (and another amp at 400Hz). This
    voltage then needs to be matched to the input of a Scott T
    transformer(I think). This is then turned from sin(x) and cos(x) to S1
    S2 and S3. Does S1 S2 and S3 come out at 90V out of the Scott T? I
    think I have it correct up to there except the voltages on S1-S3. Now I
    would personally send these three AC waves to a power amplifier (or a
    voltage amplifier first if S1-S3 are lower then 90V AC). Then after
    these power amplifiers and some circuit to detect a rotor lock, can I
    connect it to an output, or am I missing something. Other designs I
    have looked at (CCC,CSI...etc.) Seem to have a pulsed (pwm?) power
    supply that uses the boats power as a reference. What is this thing
    for? Is it necessary?

    Sorry for all the questions, and thank you for the help,
  2. Tim Wescott

    Tim Wescott Guest

    It's not clear what the 400Hz amp is doing -- are you somehow getting a
    synchro output with a 400Hz reference? That sounds oddball, but it may
    even be an off-the-shelf item for all I know.

    That depends on the Scott T. Assuming that 90V is a common standard,
    there's a good chance that it does -- but the only way to be sure is by
    careful study of the system or by measurement. Even if the Scott T is
    designed to output 90V it still must get the it's design input from the
    resolver, so you're not off the hook from measuring it or doing more
    That sounds good AFAIK. I'm not sure that rotor lock is even essential,
    except as an executive feedback / startup / BIT sort of thing.
    A switched amplifier is much more efficient than an analog amplifier.
    With todays semiconductors you can usually build a big amplifier cheaper
    by making it switched -- the semiconductors are smaller, the heatsinks
    are smaller, you don't require so much power from the rail, etc., etc.,
    etc. About the only downsides are an increased potential for radiated
    EMI and a much more complex design task.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See
  3. Matt

    Matt Guest


    Thank you for the help. I will go ahead and design an analog amp at
    first then move towards a switched on (is it simular to a switched
    power supply? 20kHz+ oscillator into a transformer?)

  4. Tim Wescott

    Tim Wescott Guest

    Ahh - you're posting from Google and you didn't read the link. Tsk tsk.

    In a way a switching power supply _is_ a switching amp, or at least it's
    a power supply _with_ a switching amp. The big difference is that a
    switching amplifier almost always needs to provide four (or at least
    two) quadrant operation, which means you have to use a half-bridge drive
    instead of a pass transistor and steering diode.

    Of course half-bridge drive means the possibility of shoot through, and
    shoot-through means little bits of FET package scattered around the lab.
    All in all it's a process that's more fun to watch than to make work.

    Web search on "switching amplifier" and "Class D amplifier" for more info.

    National and TI both have nifty parts for audio, but they only work
    within their rails and they don't have military temperature ranges.
    Apex semiconductor has nice switching amps, as long as you have a pile
    of money and a shovel.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See
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