ELEC 226, Spring 2010
Prof. Rich Kozick

Laboratory 3: More Transformers

Objective: We will experiment again with the transformers from Lab 2 and use the formulas for linear and ideal transformers, including the notes on limits of the linear transformer equations when the ideal transformer assumptions are applied.

Lab Activities:

  1. Use the outer terminals on the secondary so that the turns ratio is expected to be a=N2 / N1 = 0.1. 

  2. Use a frequency of 100 Hz and characterize your transformer at this frequency. That is, estimate the internal resistances of the primary and secondary coils (R1 and R2), the self-inductances (L1 and L2), and the coefficient of coupling, k. You should be able to estimate R1, R2, L1, and L2 quickly using the procedure from Lab 2.

  3. Compare the ratio L1 / L2 with the expected value of [N1 / N2]2 = 100.

  4. Determine how closely your transformer approximates the ideal transformer equations (a load value RL = 10 ohms should work well):






    Does the closeness of approximation vary with frequency? Try checking 100 Hz and a higher frequency.

  5. Set up the circuit shown in Problem 9.82 that you analyzed on Homework 3, and compare your measured results with the analysis. Use a potentiometer for Rx. We did not go over the solution to Problem 9.82 in class, so please ask questions during lab if you would like to review the analysis.

 

Each lab group should prepare a one-page summary of your results and discuss it with the instructor before leaving. Each student is asked to explain the steps used to estimate R1, R2, L1, L2, and M for submission as part of Homework 5 on Thursday, February 25.

Please keep your circuits assembled until you discuss the results with the instructor.