Industrial Electricity. Answer questions and/or record measurements in the spaces provided.

Transcription

1 Industrial Electricity Lab 10: Building a Basic Power Supply ame Due Friday, 3/16/18 Answer questions and/or record measurements in the spaces provided. Measure resistance (impedance actually) on each side of the transformer Primary side: Secondary side (between outside leads): Primary Secondary Secondary side (between middle lead & one outside lead: Secondary side (between middle lead & the other outside lead: Plug transformer into power cord, plug cord into wall. Connect O-scope to the two outer leads of the secondary. Sketch what you see. Use O-scope. How many volts? V P = V PP = Calculated V RMS = (from V P or V PP ) Measured V RMS = Repeat measurements using center conductor and one of the outside conductors. How many volts? V P = Calculated V RMS = V PP = (from peak or peak to peak) Measured V RMS = In general, how did the voltages compare between using the two outer conductors and using the center conductor and one of the outer conductors? In each case how did your measured RMS voltage compare with the calculated RMS voltage? Copyright 2010, David S. Mack - 1 -

2 Half-wave rectifier Draw the circuit for the half-wave rectifier Connect the circuit for the half-wave rectifier. Use a 10kΩ resistor for the load. Connect O-scope across load. Make sure you are switched to DC coupling. Sketch what you see. How many volts? V P = V PP = ote: You may want to move the vertical position of the waveform downward and switch to a smaller number of volts per division. This will give you a more accurate measurement. Does asking for V PP make sense? Why or why not? Measured voltage using DMM = Is your meter set to measure AC or DC? Which should it be set to and why? What is the frequency of the waveform of the half-wave rectifier circuit? Show your calculation below. Call the lab instructor over to discuss your results before continuing Copyright 2010, David S. Mack Initials:

3 Full-wave rectifier Sketch the circuit for the full-wave rectifier Connect the circuit for the full-wave rectifier. Use a 10kΩ resistor for the load. Connect O-scope across load. Make sure you are switched to DC coupling. Sketch what you see. How many volts using the scope? How many volts using the DMM? What is the frequency of waveform of the full-wave rectifier circuit? Show your calculation below. There are at least two things that should be evident when comparing the half-wave and full-wave rectifier circuits. Discuss them here. Copyright 2010, David S. Mack - 3 -

4 Full-wave bridge rectifier Draw the circuit for the full-wave bridge rectifier Connect the circuit for the full-wave bridge rectifier. Use a 10kΩ resistor for the load. Connect O-scope across load. Make sure you are switched to DC coupling. Sketch what you see. How many volts using the scope? How many volts using the DMM? What is the frequency of waveform of the full-wave bridge circuit? Show your calculation below. Power down the circuit and remove one of the diodes. Re-energize the circuit and sketch what you see. Discuss the differences (trade offs) between the three power supply circuits you have constructed & tested. Call the lab instructor over to discuss your results before continuing Copyright 2010, David S. Mack Initials:

5 Full-wave bridge rectifier with capacitor Add a 4.7μF capacitor in parallel with the load to the full-wave bridge rectifier circuit. Connect O-scope across output. Sketch what you see. How many volts using the scope? How many volts using the DMM?. Add another 4.7μF capacitor across the load (in parallel with the first) How does the O-scope trace change? Add a third 4.7μF capacitor across the load (in parallel with the first two) How does the O-scope trace change? What purpose is the capacitor serving? Switch the O-scope to AC coupling. Center the waveform on the screen. Expand it as big as possible. Sketch what you see What is the peak-to-peak voltage of the ripple? Pull out one of the capacitors? What happens? Why? Copyright 2010, David S. Mack - 5 -

6 Follow up Questions Recall that the turns ratio of a transformer is defined as secondary voltages are proportional to the turns ratio. VS V P S P S P. Further, recall that the primary and Assume that the input to the transformer was 120V RMS and calculate the turns ratio using the relationship above and your measurements from page 1. Show your calculation below: Another way to determine the turns ratio experimentally is shown below: Turns Ratio Z Z S p where Z P is the impedance of the primary and Z S is the impedance of the secondary. Use your impedance measurements from page 1 to calculate the turns ratio. Show your calculation and result below: Did the results compare favorably? Explain. Copyright 2010, David S. Mack - 6 -