Inductor transient response

Chapter 16.3 Inductor transient response

Lessons In Electric Circuits Volume I – DC Book
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Lessons In Electric Circuits Volume I – DC Book

  • 504CHAPTER 16. RC AND L/R TIME CONSTANTS2.500E+001.377E+01 .+..*.3.000E+001.426E+01 . +..* .3.500E+001.455E+01 .+..*.4.000E+001.473E+01 .+..*.4.500E+001.484E+01 +..*5.000E+001.490E+01 +..*5.500E+001.494E+01 +..*6.000E+001.496E+01 +..*6.500E+001.498E+01 +..*7.000E+001.499E+01 +..*7.500E+001.499E+01 +..*8.000E+001.500E+01 +..*8.500E+001.500E+01 +..*9.000E+001.500E+01 +..*9.500E+001.500E+01 +..*1.000E+011.500E+01 +..*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -As you can see, I have used the .plotcommand in the netlist instead of the more familiar.printcommand. This generates a pseudo-graphic plot of figures on the computer screen us-ing text characters. SPICE plots graphs in such a way that time is on the vertical axis (goingdown) and amplitude (voltage/current) is plotted on the horizontal (right=more; left=less). No-tice how the voltage increases (to the right of the plot) very quickly at first, then tapering offas time goes on. Current also changes very quickly at first then levels off as time goes on, butit is approaching minimum (left of scale) while voltage approaches maximum.• REVIEW:• Capacitors act somewhat like secondary-cell batteries when faced with a sudden changein applied voltage: they initially react by producing a high current which tapers off overtime.• A fully discharged capacitor initially acts as a short circuit (current with no voltage drop)when faced with the sudden application of voltage. After charging fully to that level ofvoltage, it acts as an open circuit (voltage drop with no current).• In a resistor-capacitor charging circuit, capacitor voltage goes from nothing to full sourcevoltage while current goes from maximum to zero, both variables changing most rapidlyat first, approaching their final values slower and slower as time goes on.16.3Inductor transient responseInductors have the exact opposite characteristics of capacitors. Whereas capacitors store en-ergy in an electricfield (produced by the voltage between two plates), inductors store energyin a magneticfield (produced by the current through wire). Thus, while the stored energy ina capacitor tries to maintain a constant voltage across its terminals, the stored energy in an