ELEC 2602 Lab 1 LVSIM Report Template

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Carleton University *

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Feb 20, 2024

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Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ ELEC 2602 Lab 1: Single-Phase Transformer Winter 2023 Template for Lab Report Part A: Turns Ratio, Voltage Ratio and Current Ratio A1: Electrical Isolation 6) Using the ohmmeter, measure and record the resistance between the following sets of terminals of the transformer. Terminals 1 and 2: R= _____ W Terminals 1 and 3: R= ______ W Terminals 3 and 5: R= _______ W Terminals 3 and 4: R= _____ W Terminals 1 and 7: R= ______ W Terminals 3 and 7: R= _______ W Terminals 5 and 6: R= _____ W Terminals 7 and 8: R= _____ W What is the resistance of each primary winding? R 1 = _____ W What is the resistance of each secondary winding? R 2 = _____ W Do the measurements confirm that a power transformer provides electrical isolation between its primary and secondary windings? (Note that on this ohmmeter 9999 W is essentially infinite resistance indicating an open connection or no load)  Yes  No A2: Voltage Ratio The number of turns in each of the two 24 V – 5 A windings of the power transformer in the Transformer module is 57 turns . The number of turns in each of the two 120 V – 1 A windings of the transformer is 285 turns . An ideal transformer has the following voltage ratio and following current ratio where V 1 is the voltage across winding 1 of the transformer, V 2 is the voltage across winding 2 of the transformer N 1 is the number of turns on winding 1 of the transformer and N 2 is the number of turns on winding 2 of the transformer. Using the number of turns in each winding of the power transformer specified, determine the voltage induced across windings 3-4, 5-6, and 7-8 of the transformer when a voltage of 24 V is applied to winding 1-2. Voltage V 3−4 across winding 3-4 : Voltage V 5−6 across winding 5-6: [1]

Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ Voltage V 7−8 across winding 7-8: 10) In the Metering window, measure the voltage across each winding of the transformer and record the values. Voltage V 1-2 ( E1 ) across winding 1-2 =_______ V Voltage V 3-4 ( E2 ) across winding 3-4 =_______ V Voltage V 5-6 ( E3 ) across winding 5-6 =_______ V Voltage V 7-8 ( E4 ) across winding 7-8 =_______ V Compare the voltages measured across the windings of the transformer to the ideal voltages calculated above. Are they virtually equal?  Yes  No Do the above manipulations confirm the relationship between the turns ratio and the voltage ratio?  Yes  No A3: Step-Up Transformer Calculate the following ideal ratios Tansformer turns ratio = _____= Ideal voltage ratio _____ = Ideal current ratio _____= 13) Load resistor ohmmeter reading = ________ W 14) Measurements with 120 W load Primary voltage V 1 ( (meter reading E1) = ________V-rms with 120 W load Secondary current V 2 (meter reading E2) = _________V-rms with 120 W load Primary voltage I 1 ( (meter reading I1) = __________A-rms with 120 W load Secondary voltage I 2 (meter reading I2) = __________A-rms with 120 W load Primary apparent power S 1 ( (meter reading S1) = _________VA-rms with 120 W load Secondary apparent power S 2 (meter reading S2) = _____________VA-rms with 120 W load [2]

Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ Measured results: ____ = and ____ = Is the transformer operating as a step-up transformer?  Yes  No Explain briefly the purpose of a step-up transformer _____________________________________________________________________ _______________________________________________________________________ Do the measurements confirm the relationship between the turns ratio and the voltage ratio?  Yes  No Do the measurements confirm the relationship between the turns ratio and the current ratio?  Yes  No Is the apparent power delivered to the load approximately the same as the apparent power into the primary?  Yes  No If the apparent input power and apparent output power are different, briefly explain the difference _____________________________________________________________________ _______________________________________________________________________ _____________________________________________________________________ _______________________________________________________________________ Do you expect the conclusions from this section to be different if the transformer was operated in reverse as a step- down transformer?  Yes  No Explain your answer briefly. _______________________________________________________________________ _______________________________________________________________________ Recall the impedance transformation property of a transformer. ________x________=________ W For the 120 W load, calculate what the primary current should be since _____________ = _____________A-rms Does the calculated result agree approximately with the measured result?  Yes  No Part B: Transformer Winding Polarity [3]

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Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ 16) Terminals with the same polarity as terminal 1 are : _________________ 17) Ohmmeter reading = ________ W 19) Oscilloscope measurements Peak value of E1 = ______V RMS value of E1= ______V-rms Peak value of E2 = ______V RMS value of E1= ______V-rms Peak value of E3 = ______V RMS value of E1= ______V-rms Peak value of E4 = ______V RMS value of E1= ______V-rms 20) Insert print of oscilloscope display here. (surname_studentnumber_oscilloscope1.pdf) Are all the waveforms in phase?  Yes  No Using the x-axis (time-axis) units and the interval between peaks, calculate the frequency of the waveforms. Period T of waveform = ______divisions x ______ seconds/division = _______ seconds Frequency f = 1/T = ___________Hz. Does the measured frequency agree with the set frequency?  Yes  No 21) Phase analyzer measurements Phase of E1 = _______ degrees Phase of E2 = _______ degrees Phase of E3 = _______ degrees Phase of E4 = _______ degrees Do the voltage phasors displayed in the Phasor Analyzer confirm what you observed using the Oscilloscope ?  Yes  No 23) The leads at voltage E3 of the DACI have been reversed. Insert print of oscilloscope display here. (surname_studentnumber_oscilloscope2.pdf) [4]

Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ Is waveform E3 essentially 180 degrees out of phase with E1, E2 and E4  Yes  No 24) Phase analyzer measurements Phase of E1 = _______ degrees Phase of E2 = _______ degrees Phase of E3 = _______ degrees Phase of E4 = _______ degrees Do the voltage phasors displayed in the Phasor Analyzer confirm what you observed using the Oscilloscope ?  Yes  No Part C: Interconnection of Transformer Windings 27) Different series connections of secondary windings Voltage across windings 3-4 and 5-6 ( E2 ) in Figure 7a = _______ V Voltage across windings 3-4 and 5-6 ( E2 ) in Figure 7b = _______ V Voltage across windings 5-6 and 7-8 ( E2 ) in Figure 7c = _______ V Explain these results by addition or subtraction of the two secondary voltages: In Fig 7a _______________________________________________________________ In Fig 7b _______________________________________________________________ In Fig 7c _______________________________________________________________ Part D: Determine Winding Polarity Using a Voltmeter. [5]

Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ 30) Voltage measured across windings 1-2 and 5-6 in Fig 8a = _______ V 32) Voltage measured across windings 1-2 and 7-8 in Fig 8b =_______ V 34) Primary voltage V 1 ( (meter reading E1) = _____________V-rms in Fig. 9a Secondary voltage V 2 (meter reading E2) = _____________V-rms in Fig. 9a Primary current I 1 (meter reading I1) = _____________A-rms in Fig. 9a Secondary current I 2 (meter reading I2) = _____________A-rms in Fig. 9a Primary apparent power S 1 (meter reading S1) = _____________VA-rms in Fig. 9a Secondary apparent power S 2 (meter reading S2) = _____________VA-rms in Fig. 9a 36) Primary voltage V 1 ( (meter reading E1) = _____________V-rms in Fig. 9b Secondary voltage V 2 (meter reading E2) = _____________V-rms in Fig. 9b Primary current I 1 ( (meter reading I1) = _____________A-rms in Fig. 9b Secondary current I 2 (meter reading I2) = _____________A-rms in Fig. 9b Primary apparent power S 1 ( (meter reading S1) = _____________VA-rms in Fig. 9b Secondary apparent power S 2 (meter reading S2) = _____________VA-rms in Fig. 9b Current in winding 5-6 measured by I3 = ________ A-rms Current in winding 7-8 measured by I4 = ________ A-rms [6]

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Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ Is the current flowing in each winding virtually equal to 0.5 A, thereby indicating that each winding is sharing the load current equally?  Yes  No Has the apparent power delivered to the load approximately doubled from the connection in step 34?  Yes  No Explain your result briefly _______________________________________________________________________ _________________________________________________________________________ _______________________________________________________________________ _________________________________________________________________________ Part E: Transformer Losses, Efficiency and Voltage Regulation Use circuit in Figure 9b, 39) No load condition Primary voltage V 1 ( (meter reading E1) = __________V-rms no-load Secondary voltage V 2 (meter reading E2) = ___________V-rms no-load Primary current I 1 ( (meter reading I1) = ____________A-rms no-load Secondary current I 2 (meter reading I2) = _____________A-rms no-load Secondary current I 3 (meter reading I3) = _____________A-rms no-load Secondary current I 4 (meter reading I4) = _____________A-rms no-load Primary active power P 1 ( (meter reading P1) = _____________W no-load Secondary active power P 2 (meter reading P2) = ___________W no-load 41) and 43 ) Insert data table surname_studentnumber_Data_table.txt here. 44) Open an Excel spreadsheet and import the Data Table text file. You should rearrange the columns in the order V1, I1, P1 ,V2, I2, P2, I3, I4 In the spreadsheet application, add a new column to the results: the transformer power losses PLOSS (W). Calculate the transformer power losses by subtracting the secondary active power P2 (i.e., the active power delivered to the load by the transformer) from the primary active power P1 (i.e., the active power supplied to the transformer by the ac power source). Add another column to the results: the transformer efficiency h (%). Calculate the transformer efficiency by dividing the secondary active power P2 by the primary active power P1, then multiply the result by 100 to obtain the [7]

Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ efficiency h in percentage. Add another column for the copper loss PCu1 in the primary winding. Use the measured resistance of each primary winding from step 6. to calculate Add another column for the copper loss PCu2 in the secondary winding. Use the measured resistance of the secondary winding from step 6 to calculate . Add another column for the total copper loss PCu = PCu1+PCu2 in both windings. Add another column for other losses POTHER = PLOSS-PCu 46) Plot a graph of the transformer power losses PLOSS as a function of the secondary (load) current I2. Insert Graph here. Observe the graph. Describe the relationship between the transformer power losses and the transformer secondary (load) current. Briefly explain. ___________________________________________________________________________________ ___________________________________________________________________________________ __________________________________________________________________________________ What source of loss explains the difference POTHER between the total transformer power loss and the total copper loss? ___________________________________________________________________________________ ___________________________________________________________________________________ _________________________________________________________________________________ 47) Plot a graph of the transformer efficiency 𝜂 as a function of the secondary (load) current I2. Insert Graph here. Observe the graph. What happens to the transformer efficiency 𝜂 at low values of the secondary (load) current? Briefly explain. ___________________________________________________________________________________ ___________________________________________________________________________________ __________________________________________________________________________________ Are power transformers high-efficiency devices? Explain briefly. ___________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________________ __________________________________________________________________________________ 48) Plot the transformer voltage regulation curve, i.e., a graph of the transformer secondary (load) voltage V2 as a function of the secondary (load) current I2. [8]

Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ Insert Graph here. Observe the graph. Describe the relationship between the transformer secondary (load) voltage V2 and the secondary (load) current I2. Briefly explain. ___________________________________________________________________________________ ___________________________________________________________________________________ __________________________________________________________________________________ 49) Calculate the voltage regulation of the power transformer, using the values recorded in this section. Recall that voltage regulation is given by ___________________x100% = _______% Questions and Discussion 1) A power transformer has 125 turns of wire in one of its windings, and 375 turns of wire in the other. What is the transformer turns ratio when it is used as a step-up transformer? What is the transformer turns ratio when it is used as a step-down transformer? _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 2) A step-up transformer connected to a resistive load has 300 turns of wire in the primary winding and 1000 turns of wire in the secondary winding. Determine the current flowing in the secondary winding of the transformer when a current of 3 A flows in the primary winding. _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 3) A step-down transformer has 480 turns of wire in the primary winding and 120 turns of wire in the secondary winding. Determine the voltage across the primary winding of the transformer when a voltage of 60 V is measured across the secondary winding of the transformer. _________________________________________________________________________________________ ________________________________________________________________________________________ 4) Why is it important to know the polarity of each winding of a power transformer before connecting the transformer windings in series? _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ [9]

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Name ___________________________________ Student Number_____________ Lab Section_____ Date Lab Performed _____________________ Date Lab Report Submitted _____________________ 5) A voltage of 60 V is measured across the primary winding of a step-up transformer while a voltage of 300 V is measured across the secondary winding. Given that a current of 2.5 A flows in the primary winding of the transformer, calculate the current flowing in the secondary winding. _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 6) Consider a power transformer having a single primary winding with a nominal voltage of 50 V connected to a 25 V ac power source, as well as twob secondary windings with nominal voltages of 125 V and 225 V connected in series. Assuming that the ends of the windings that are connected in series are of the same polarity, calculate the total voltage induced across the secondary windings when the ac power source is turned on. _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 7) How can the polarity of two transformer windings be determined using a voltmeter? _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 8) What is the effect of connecting the secondary windings of a power transformer in parallel? _________________________________________________________________________________________ ________________________________________________________________________________________ 9) What is the magnetizing current of a power transformer? Explain briefly. _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 10) What is the difference between copper losses and iron losses in a power transformer? _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 11) What is the relationship between the power losses and the load current of a power transformer? Explain briefly _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 12) Are power transformers ideal devices, i.e., is their efficiency equal to 100%? Explain briefly. _________________________________________________________________________________________ _________________________________________________________________________________________ ________________________________________________________________________________________ 13) Explain what the voltage regulation down of a power transformer means. _________________________________________________________________________________________ _________________________________________________________________________________________ [10]