Delta to Wye Conversion Using Real Components
OEES 110

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This experiment is going to take a little longer than usual, but it's worth more points than usual.
  1. In the upper left-hand corner of a breadboard, build a delta circuit using the following resistors: Ra = 22k, Rb = 33k, and Rc = 47k.
  2. Connect a 12 V. power supply across the following two points:
    • The point where Ra and Rc are connected.
    • The point where Rc and Rb are connected.
  3. Connect a 10k resistor across the following two points:
    • The point where Ra and Rb are connected.
    • The point where Rb and Rc are connected.
  4. Measure the voltage across the 22k resistor and write it here: _______________
  5. Measure the voltage across the 33k resistor and write it here: _______________
  6. Remove the 12 V. from the circuit, and also remove the 10k resistor. However, don't disconnect the other resistors.
  7. Using the formulas on p. 280, calculate resistor values for an equivalent wye circuit.
  8. Find resistors that are a little larger than the values you calculated.
  9. Click here to download a spreadsheet that will help you get accurate resistance values by using trim resistors.
  10. For each resistor, use the spreadsheet to calculate a parallel trim resistor to get close to the values needed for the wye circuit.
  11. Find actual trim resistors that are reasonably close to those calculated by the spreadsheet.
  12. Put these trim resistor values into the spreadsheet.
  13. If  the error is larger than 2%, see me.
  14. Build the wye circuit using the parallel combinations you determined.
  15. With an ohmmeter, measure each parallel combination to see how close it is to the desired value.
  16. If a parallel combination is too large, try a smaller trim resistor. If it's too small, try a larger trim resistor.
  17. Connect a 12 V. power supply across the following two points:
    • The free end of R2.
    • The free end of R1.
  18. Connect a 10k resistor across the following two points:
    • The free end of R3.
    • The free end of R1.
  19. Measure the voltage across the following two points and write it here: ____________
    • The free end of R2.
    • The free end of R3.
  20. Measure the voltage across the following two points and write it here: ____________
    • The free end of R3.
    • The free end of R1.
  21. The above two voltages should be reasonably close to the voltages you measured in the delta circuit.
 
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