# Homework Assignment 12

## Due Lecture 41

#### ECEN 4797 and 5797 assignment

1. Do textbook Problem 13.6. Notes: The two-transistor forward converter is illustrated in Fig. 6.27, not 6.28. As discussed in class, in the forward converter, you can assume that Delta_B = Bmax/2. For an example of estimating core loss: see pp. 561 to 562 of the textbook (2nd edition). In this problem you can ignore skin and proximity effects. The copper losses can be calculated simply as R1*I1^2 + R2*I2^2, where R1 and R2 are the dc resistances of the primary and secondary, respectively, and I1 and I2 are the rms currents of the primary and secondary, respectively. You may neglect the transformer magnetizing current, and you may assume that the output filter inductor current ripple is small.

2. Do textbook Problem 13.10.

• Notes on Problem 13.10:
• The core has negligible reluctance
• For part (b), you may either graphically estimate the answers using Fig. 13.31 or 13.32, or you may exactly evaluate the equations of Section 13.4.4. Don't be afraid of Eqs. (13.75) to (13.81): they aren't hard to evaluate with a calculator or spreadsheet
• For part (c): you may assume that every primary and secondary layer has the same dc resistance Rdc (i.e., every layer is wound with the same size wire).
• It is suggested that you read the example of Section 13.4.6.

3. Do the attached additional Proximity loss problem.