The NØPU Big Quiz

Discussion in 'General Technical Questions and Answers' started by N0PU, Jan 9, 2003.

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  1. AE4FA

    AE4FA Ham Member QRZ Page

    Hmmm. That was less than complete. I’ll try again.

    Flux density is a function of current through the coil and the permeability of the core material. There are really two things that can be done to alter it.

    The first is really mechanical. A powdered iron core can be threaded into the coil. We can then control permeability, and therefore flux density, by adjusting the depth that the core is inserted into the coil. It can be set up so that part of the core is air, while the rest is powdered iron.

    The second is truly electrical. Increasing current through a powdered iron core inductor increases flux density. Increasing it enough gets to the saturation point. All the available molecules are now magnetized. None are left to accommodate more lines of flux. And, as Harry noted, permeability is diminished to 1.

    So, regulating current flow acts to regulate the permeability of the core, and – by extension – the inductance of the coil, and – by further extension – the reactance of the inductor, and therefore the impedance of the circuit, which controls power to the load.
     
  2. N0PU

    N0PU Ham Member QRZ Page

    </span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ae4fa @ June 07 2003,08:07)</td></tr><tr><td id="QUOTE">Hmmm.  That was less than complete.  I’ll try again.

    Flux density is a function of current through the coil and the permeability of the core material.  There are really two things that can be done to alter it.

    The first is really mechanical.  A powdered iron core can be threaded into the coil.  We can then control permeability, and therefore flux density, by adjusting the depth that the core is inserted into the coil.  It can be set up so that part of the core is air, while the rest is powdered iron.

    The second is truly electrical.  Increasing current through a powdered iron core inductor increases flux density.  Increasing it enough gets to the saturation point.  All the available molecules are now magnetized.  None are left to accommodate more lines of flux.  And, as Harry noted, permeability is diminished to 1.

    So, regulating current flow acts to regulate the permeability of the core, and – by extension – the inductance of the coil, and – by further extension – the reactance of the inductor, and therefore the impedance of the circuit, which controls power to the load.[/QUOTE]<span id='postcolor'>
    Right...
    FA: 10 points
    ---------------------------

    Question 420

    Define a saturable-core reactor.
     
  3. AE4FA

    AE4FA Ham Member QRZ Page

    A Saturable Core Reactor is basically a transformer core with two windings – a Control Winding and a Load Winding. It acts as an inductance control circuit. Power to the control winding is fed through a variable resistor, so that current through the winding can be adjusted by varying circuit resistance. Since the load winding is on the same core, output to the load can be controlled. Adjusting the control circuit sets up the core’s permeability, and therefore the inductance of the load winding.

    Assuming the control circuit is set up for the proper operating range, decreasing control winding resistance decreases core permeability – and causing inductance to drop. Increasing control winding resistance has the opposite effect.
     
  4. N0PU

    N0PU Ham Member QRZ Page

    </span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ae4fa @ June 08 2003,05:42)</td></tr><tr><td id="QUOTE">A Saturable Core Reactor is basically a transformer core with two windings – a Control Winding and a Load Winding.  It acts as an inductance control circuit.  Power to the control winding is fed through a variable resistor, so that current through the winding can be adjusted by varying circuit resistance.  Since the load winding is on the same core, output to the load can be controlled.  Adjusting the control circuit sets up the core’s permeability, and therefore the inductance of the load winding.  

    Assuming the control circuit is set up for the proper operating range, decreasing control winding resistance decreases core permeability – and causing inductance to drop.  Increasing control winding resistance has the opposite effect.[/QUOTE]<span id='postcolor'>
    Right...
    FA: 10 points
    --------------------------

    Question 421

    Explain the operation of the three-legged saturable-core reactor.
     
  5. AE4FA

    AE4FA Ham Member QRZ Page

    It’s about the same difference as between a 2 legged stool and a 3 legged stool. You can balance on a 2 legged stool okay until you shift your weight.

    Given a DC control circuit and an AC load circuit, the flux generated by the control circuit is of the same polarity as the load half the time. The other half, the flux generated by the control circuit Is opposing flux generated by the load circuit. This would throw the control circuit out of calibration, and it would not operate properly.

    A 3 legged saturable core reactor solves this by using one control winding and two load windings. These are set up so that the flux generated in the two load windings cancel one another – and thus do not affect the control circuit flux. Balance is stable regardless of the AC load signal’s phase.
     
  6. N0PU

    N0PU Ham Member QRZ Page

    </span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ae4fa @ June 08 2003,18:31)</td></tr><tr><td id="QUOTE">It’s about the same difference as between a 2 legged stool and a 3 legged stool.  You can balance on a 2 legged stool okay until you shift your weight.

    Given a DC control circuit and an AC load circuit, the flux generated by the control circuit is of the same polarity as the load half the time.  The other half, the flux generated by the control circuit Is opposing flux generated by the load circuit.  This would throw the control circuit out of calibration, and it would not operate properly.

    A 3 legged saturable core reactor solves this by using one control winding and two load windings.  These are set up so that the flux generated in the two load windings cancel one another – and thus do not affect the control circuit flux.  Balance is stable regardless of the AC load signal’s phase.[/QUOTE]<span id='postcolor'>
    Right...
    FA: 10 points
    -------------------------

    Question 422

    Describe a half-wave magnetic amplifier.
     
  7. AE4FA

    AE4FA Ham Member QRZ Page

    Basically a 3 legged saturable core reactor with a rectifier diode in the output circuit. As with any half-wave rectifier circuit, it conducts during only half the cycle.
     
  8. N0PU

    N0PU Ham Member QRZ Page

    </span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ae4fa @ June 08 2003,20:22)</td></tr><tr><td id="QUOTE">Basically a 3 legged saturable core reactor with a rectifier diode in the output circuit.  As with any half-wave rectifier circuit, it conducts during only half the cycle.[/QUOTE]<span id='postcolor'>
    Right:
    FA: 10 points
    -----------------------------

    I leave it to the students to study full-wave mag amps... These are not devices that Hams normally use... but I thought the exposure would be good...

    Question 423

    Define Resonance as used in tuned circuits.

    [yes, we changed chapters!]
     
  9. AE4FA

    AE4FA Ham Member QRZ Page

    Resonance is that point at which inductive reactance and capacitive reactance cancel each other out, leaving a purely resistive load.
     
  10. N0PU

    N0PU Ham Member QRZ Page

    </span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ae4fa @ June 08 2003,20:44)</td></tr><tr><td id="QUOTE">Resonance is that point at which inductive reactance and capacitive reactance cancel each other out, leaving a purely resistive load.[/QUOTE]<span id='postcolor'>
    Riight...
    FA: 10 points
    -------------------------

    Question 424

    Describe the effects of frequency on L, C and R.
     
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