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— | university:courses:electronics:rl_transient_response [23 Aug 2019 11:01] – Pop Andreea | ||
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+ | ======Activity: | ||
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+ | =====Objective: | ||
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+ | The objective of this Lab activity is to study the transient response of inductor circuits using a series RL configuration and understand the time constant concept. | ||
+ | =====Background: | ||
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+ | This lab activity is similar to the " | ||
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+ | Time Constant (t): It is a measure of time required for certain changes in voltages and currents in RC and RL circuits. Generally, when the elapsed time exceeds five time constants (5t) after switching has occurred, the currents and voltages have reached their final value, which is also called steady-state response. | ||
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+ | The time constant of an RL circuit is the equivalent inductance divided by the Thévenin resistance as viewed from the terminals of the equivalent inductor. | ||
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+ | <m>t = L / R</m> (1) | ||
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+ | A Pulse is a voltage or current that changes from one level to another and back again. If a waveform' | ||
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+ | The relation between pulse width and frequency for the square wave is given by: | ||
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+ | < | ||
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+ | {{ : | ||
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+ | <WRAP centeralign> | ||
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+ | In an R-L circuit, voltage across the inductor decreases with time while in the RC circuit the voltage across the capacitor increased with time. Thus, current in an RL circuit has the same form as voltage in an RC circuit: they both rise to their final value exponentially according to 1 - e < | ||
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+ | The expression for the current in the Inductor is given by: | ||
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+ | < | ||
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+ | where, V is the applied source voltage to the circuit for t = 0. The response curve is increasing and is shown in figure 2. | ||
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+ | {{ : | ||
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+ | <WRAP centeralign> | ||
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+ | (Time axis normalized by t) | ||
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+ | The expression for the current decay across the Inductor is given by: | ||
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+ | < | ||
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+ | where, | ||
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+ | I< | ||
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+ | L/R = t is time constant. | ||
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+ | The response curve is a decaying exponential and is shown in figure 3. | ||
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+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
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+ | Since it is possible to directly measure the current through the Inductor ( current supplied by driving source ) with the ALM1000, we will measure and compare both the current and the output voltage across the Resistor. The resistor waveform should be similar to the inductor current as V< | ||
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+ | Here, R< | ||
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+ | R inductance is the measured value of inductor resistance and can be measured by connecting inductance to an ohmmeter prior to running the experiment. | ||
+ | =====Materials: | ||
+ | ADALM2000 Active Learning Module\\ | ||
+ | Solder-less breadboard, and jumper wire kit\\ | ||
+ | 1 100 Ω resistor\\ | ||
+ | 1 1 mH inductor\\ | ||
+ | |||
+ | =====Hardware setup:===== | ||
+ | Set up the circuit shown in Figure 4 on your solderless breadboard with the component values R1 = 100Ω and L1 = 1 mH. | ||
+ | {{ : | ||
+ | <WRAP centeralign> | ||
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+ | {{: | ||
+ | <WRAP centeralign> | ||
+ | =====Procedure: | ||
+ | On Channel 1 of the oscilloscope you will visualize the input voltage, and on channel 2 the voltage on the resistor(it has the same shape as the current through the inductor). Generate a square wave on the channel 1 of the signal generator with 4V amplitude peak-to-peak. The frequency will be set according to t. Calculate the applied frequency using equation (2) for tp = 5t. | ||
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+ | {{ : | ||
+ | <WRAP centeralign> | ||
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+ | The waveform on channel 2 (voltage on the resistor) has the same shape as IL(t) waveform. From it, measure time constant t and compare with the one that you calculated from L/Rtotal. (Hint: Find the time that corresponds to 0.63VR value). | ||
+ | Observe the response of the circuit and record the results again for tp = 25t, and tp = 0.5t. | ||
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+ | ====Questions: | ||
+ | • Include plots of IL and VR for different tp values given above in Procedure 4. | ||
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+ | • A Capacitor stores charge. What do you think an Inductor stores? Answer in brief. | ||
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+ | • How can you attenuate the spikes present on the input voltage? | ||
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+ | <WRAP round download> | ||
+ | **Lab Resources: | ||
+ | * Fritzing files: | ||
+ | * LTSpice files: | ||
+ | </ | ||
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+ | **Return to Lab Activity [[university: | ||