EE214 Experiment 3 Spring 2017 R PDF

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EE 214 Electronic Circuits Laboratory

Spring 2016

EXPERIMENT III TRANSFORMERS & MATLAB WORKSHOP Objectives In this experiment, different transformer circuits will be examined and transformer parameters will be determined using a short circuit test. In the workshop part, a square wave will be obtained from the summation of sine waves using MATLAB. Preliminary Work 1. Study the document, titled “Notes on Transformers”, available on OSTUClass. 2. Study the MATLAB tutorial, titled “Introduction to MATLAB”. Read the experimental procedure; you are expected to write a script together with your partner during the laboratory session to accomplish the task indicated. You are responsible for learning the usage of the given MATLAB functions before the laboratory sessions. Note that MATLAB is available in Students’ PC Lab. No preliminary work will be collected for this week; but you will be responsible for both topics for the quiz, and you are expected to have learned enough to be able to carry out both parts of the experiment, so please come prepared.

Experimental Procedure 1. In this question, you will observe the step down operation of the transformer under no load. For the following circuit, using a sinusoidal input voltage with a peak voltage of 10 V and frequency of 50Hz, obtain and plot the output voltage. Determine the turn ratio N1/N2 and comment on the

results. 2.

With the same input voltage as in the previous step, construct circuit in Figure 2 with Rload = 56Ω Measure iin, vout, iout and calculate input and output powers Pin and Pout. Explain why Pout≠Pin.

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Increase the frequency to 1 kHz and repeat the step. Comment on the results. 3. With secondary side short circuited, an approximate equivalent circuit of the transformer reflected

to the primary side is given as given in Figure 3 where 𝑋1 = 𝜔𝐿1 , 𝑟2 ′ = 𝑛 2 𝑟2 , 𝑋2 ′ = 𝑛2 𝜔𝐿2 , 𝑛 =

𝑁1 /𝑁2 and 𝜔 = 100𝜋. Plot 𝑖𝑠𝑐 (𝑡) and 𝑉𝑠𝑐 (𝑡) on the same graph. Determine the transformer parameters 𝑟1 , 𝑟2 , 𝐿1 and 𝐿2 assuming that 𝑟1 = 𝑟2 ′ and 𝑋1 = 𝑋2 ′. Show your calculations. DO NOT forget to limit the peak to peak voltage of the input to 1V in order to prevent high currents from passing through the transformer.

4.

Transformers can be used to match impedances. Consider the circuit given in Figure 4. In this circuit, power is meant to transfer from the previous circuit stage, whose Thevenin equivalent is represented by vin and 1 k resistor, to the 10  load, which may represent a loud speaker. Note that if 1k and 10 resistors were directly connected in series, power transferred to the load would be significantly small. Utilizing such a circuit increases the load power significantly.

Construct the circuit of Figure 4 and calculate the power dissipated on the 10  resistor. Then connect the 1 k and 10  resistors directly in series without the transformer and do the same calculation. Comment on the results.

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EE 214 Electronic Circuits Laboratory

Spring 2016

5. MATLAB Workshop

A square wave is a periodic waveform which can be represented as an infinite summation of sinusoidal waves. Using Fourier expansion with cycle frequency f over time t, we can represent an ideal square wave with an amplitude of 1 as an infinite series of the form 𝑣𝑠𝑞𝑢𝑎𝑟𝑒 (𝑡) =

4 1 1 (sin(2𝜋𝑓𝑡) + sin(6𝜋𝑓𝑡) + sin(10𝜋𝑓𝑡) + … ) 𝜋 3 5

Figure 5: Square wave built from sum of sine waves.

    

Create a sine wave of 𝑣1 = 7.5𝑠𝑖𝑛(200𝜋𝑡) using the Agilent signal generator. Measure the signal using the DSO, push 50% button to adjust the trigger level and set time division to 2 ms/div. Obtain the DSO screen on the computer (DSO3000 program) and export the channel measurements as .xls file. In this file, find all commas “,” and replace them with dots “.”. Create a sine wave of 𝑣1 = 2.5𝑠𝑖𝑛(600𝜋𝑡) using the Agilent signal generator. Measure the signal using the DSO, push 50% button to adjust the trigger level and set time division to 2 ms/div. 3

      

Obtain the DSO screen on the computer (DSO3000 program) and export the channel measurements as .xls file. In this file, find all commas “,” and replace them with dots “.”. Create a sine wave of 𝑣1 = 1.5𝑠𝑖𝑛(1000𝜋𝑡) using the Agilent signal generator. Measure the signal using the DSO, push 50% button to adjust the trigger level and set time division to 2 ms/div. Obtain the DSO screen on the computer (DSO3000 program) and export the channel measurements as .xls file. In this file, find all commas “,” and replace them with dots “.”. Open the MATLAB program on the desktop. Create an m-file and write your commands on the script. It is more time-saving. Use the following command to parse measured data from each .xls file. [number voltage_values time] = textread(‘file.xls’,’%f %f %f’,’Headerlines’,8);

    

Plot 𝑣1 , 𝑣2 and 𝑣3 on the same figure with 3-by1 grid by using “subplot(m,n,p)” command. Plot 𝑣1 , 𝑣1 + 𝑣2 and 𝑣1 + 𝑣2 + 𝑣3 on the same figure with 3-by1 grid by using “subplot(m,n,p)” command. Each graph should have a title and axis names y-axis of each graph should be limited between +10 volt and -10 volt and x-axis should be limited between -120 ms and +120 ms You will use “plot(.)”, ”title(.)”, “xlabel(.)”, “ylabel(.)”, “ylim(.)” and “xlim(.)” functions. You can get information and example for all functions by using help feature of MATLAB.

Equipment List Oscilloscope, Signal Generator, Digital Multimeter, Computer Transformer Resistors (10, 56, 1 k)

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EE 214 Electronic Circuits Laboratory

Spring 2016

Student 1 : Student 2 : Assistant :

Group: Date:

EXPERIMENT IV IMPEDANCE MEASUREMENT AND COMPLEX POWER Experimental Results 1.

n = N1/N2 = Comments:

2. For 50 Hz

𝑖𝑖𝑛 = 𝑖𝑜𝑢𝑡 = 𝑉𝑜𝑢𝑡 =

For 1 kHz 𝑖𝑖𝑛 = 𝑖𝑜𝑢𝑡 = 𝑉𝑜𝑢𝑡 =

𝑃𝑖𝑛 = 𝑃𝑜𝑢𝑡 =

Comments:

3.

Calculations:

𝑟1 = 𝑟2 =

𝐿1 = 𝐿2 = 5

𝑃𝑖𝑛 = 𝑃𝑜𝑢𝑡 =

4.

With transformer,

𝑃𝑜𝑢𝑡 =

Without transformer,

𝑃𝑜𝑢𝑡 =

Comments:

5.

Comments:

Conclusion

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