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ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 Name ___________________ Section ______________ The Phasor Lab OBJECTIVE: The objective of this experiment is to measure the complex voltages and the current in a series resistive-capacitive-inductive circuit and draw a phasor diagram showing all the node voltages and the current. Kirchhoff's voltage law will also be checked for the same circuit. COMPONENTS AND EQUIPMENT: 1. Oscilloscope 2. Function Generator 3. Digital Multimeter BACKGROUND: In an alternating current(AC) circuit containing reactive elements, currents and voltages are complex with a magnitude and a relative angular position. Actually, the angular position represents a difference in time between sinusoids (a phase difference). This can be clearly seen on a two channel oscilloscope. The period of a sinusoid is the time to complete one cycle or 360⁰ of the wave. The relationship between the complex currents and voltages in a circuit can be shown on a phasor diagram. This relationship allows the time between the two sinusoids to be expressed in degrees by the equation: 1 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 Figure 1 - Phase angle measurement PROCEDURE: 1. Turn on all equipment to be used in this experiment as early as possible and leave it on. This will allow the instruments to warm up and stabilize. 2. In figure 2, the voltage source is 3Vrms operating at 1200Hz. Calculate the voltage magnitude and phase at Node 1 (use node 1 as the reference phase, ie phase is zero degrees), Node 2, and Node 3 on a blank sheet or space below. Use voltage divider to solve the circuit. Make sure you submit your calculation. 2 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 V1 = node 1 voltage set to 3VRMS at 1200 Hz. C1= 224nF L1 = 210mH R2 = The internal alternating-current resistance of the inductance (measure by DMM) R3 = 1kΩ 3 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 3. Set up the circuit shown in Figure 2. The nominal values of the components are given under the figure. As usual in this course these values need not be matched exactly but they will be measured closely. Place the measured values in Table D1. 4. With the circuit connected to the function generator adjust the terminal voltage of the function generator to 3.00 volts rms. Use the oscilloscope to set the frequency to 1200 Hz. 5. Use a digital multimeter to measure the potential at nodes 1, 2, and 3 with respect to ground. Determine the current from the potential at Node 3. Also measure the potential from node 1 to node 2 and the voltage from node 2 to node 3. Place the results in Table D-2. 6. Using an oscilloscope, and again using node 1 as the reference node, measure the peakto-peak potential at nodes 1, 2, and 3. Also determine the current. Assuming the voltage at Node 1 is at zero degrees (i.e. this will be the reference phasor and will be placed at zero degrees on the phasor diagram), measure the phase angle of the potential at Nodes 2 and 3 and the phase angle of the current. Place the raw data in Table D-3. 7. Exchange Cl and R3 to be able to measure the voltage magnitude and phase of the capacitor. Measure the magnitude and phase angle of the potential across Cl still using the node 1 voltage as the reference. Replace C 1 and exchange the inductance (L 1 and R2) with R3. Measure the magnitude and phase angle of the potential across the inductance. Place the results of these measurements in Table D-3. Why was the capacitor and resistance switched? Result and Analysis Normally when doing an experiment the data is placed on a data sheet which has been prepared in advance such as this one. It should be recorded in a notebook for future reference. This data is taken and recorded in such a way as to reduce the chance of error and generally is not in the best form to be included in a report. List the equipment used in this experiment. Give the manufacturer and model for each instrument. The exact unit can be identified by giving the station number. The equipment is listed in such a way that the experimenter can find the exact instrument used for each measurement. If the data is not as expected, the instruments used can be checked to see if they are appropriate ( ie does it have the proper frequency range) or if they are out of calibration. _______________________________________________________ _______________________________________________________ 4 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 _______________________________________________________ _______________________________________________________ _______________________________________________________ 1. Using the raw data in Tables D-2 and D-3 find the measured values of the voltages and current in Figure I. The magnitudes measured with the digital multimeter are probably more accurate than those measured with the oscilloscope. Potential Measured Calculated Magnitude Phase Angle Magnitude Percent Error Phase Angle Magnitude Phase Angle Node 1 Node 2 Node 3 Voltage Across C (VC) Voltage Across L (VL) 2. Draw a phasor diagram for the circuit of Figure 1 for Node 3 voltage. Label the title, magnitude, and angle including unit. Label the axis (real and imaginary). 5 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 3. Kirchhoffs Voltage Law states that the sum of the voltages around a closed loop must add to zero. In direct-current circuits this sum is algebraic. In an alternating current circuit the sum must consider the phase of each potential. This means that the sum of all the real parts, and the sum of the imaginary parts, of the voltages around a closed loop must each add to zero. Potential across Real Part volts Imaginary Part volts Function Generator C1 (from Step 7) L1 (from Step 7) R3 KCL Sum (VS-VL-VC-VR) Data Sheet 6 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 Table D-1 Measure value of the component: Component Measured Value C1 L1 R2 R3 Table D-2 Magnitude of the Node Potentials and the Current In Figure 1. Measured with a DMM Reading (indicate if this is RMS value) Terminal Potential – Node 1 Potential at Node 2 Potential at Node 3 Potential at N1 to N2 Potential at N2 to N3 Current Table D-3. Circuit Potentials and Currents in Figure 1. Measured with an Oscilloscope Voltage magnitude Phase shift time Scale (1X, 10X, 100X) 7 ECE 213 Electrical Circuits Lab II LAB #5 Spring 2017 Node 1 Node 2 Node 3 Potential across C1 (step7) Potential across L (Step 7) 8