Refer to the temperature controller of Fig. 17.13a. Sketch the waveform of the full-wave r...

Refer to the temperature controller of Fig. 17.13

a. Sketch the waveform of the full-wave rectified waveform across the SCR.

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b. What is the peak current through the heater when the SCR is “on” and has a short-circuit equivalent between anode and cathode? Assume each diode has a drop of 0.7 V when conducting.

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c. When the SCR is on, what is the maximum current through the thermostat?

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d. What is the total time for the rise time of the positive pulse of the applied ac voltage from 0 V to the maximum voltage of the rectified signal?

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e. What is the time constant of the capacitor that is charging during the same period of part (d)? How do they compare? Why is this a concern?

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f. What is the state of the SCR during this charging period? Why?

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g. If the gate-firing potential is 40 V, what is the time period between successive triggering of the SCR?

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h. Once the thermostat reaches its set temperature and assumes the short-circuit state, how will the SCR react?

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i. What method was used to turn the SCR off: anode current interruption or forced commutation?

FIG. 17.13 Temperature controller.