1 / 16

EE301 AC Thèvenin and Max Power Transfer

Learn Thévenin's Theorem for AC circuits, conditions for max power transfer, calculate load impedance for max power transfer, solve example problems, and review conjugates in AC circuits.

marykirk
Download Presentation

EE301 AC Thèvenin and Max Power Transfer

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EE301AC Thèvenin andMax Power Transfer

  2. Learning Objectives • Apply Thèvenin’s Theorem to AC circuits • Explain under what conditions a source transfers maximum power to a load • Determine the value of load impedance for which maximum power is transferred from the circuit

  3. ETh is the open circuit voltage at the terminals, ZTh is the input or equivalent resistance at the terminals when the independent sources are turned off. Thévenin’s theorem for AC

  4. Remove the load (open-circuit) and measure the resulting voltage. Review Determining ETh Eth = open ckt voltage

  5. With the load disconnected, turn off all independent sources. Voltage sources – 0 V is equivalent to a short-circuit. Current sources – 0 A is equivalent to a open-circuit. ZTh is the equivalent resistance looking into the “dead” circuit through terminals a-b. Determining ZTh Zth

  6. Once ETh and ZTh have been found, the original circuit is replaced by its equivalent and solving for ILD and VLD becomes trivial. Applying Thévenin equivalent

  7. Example Problem 1 Convert the source below into a Thévenin equivalent and determine the current through load Zab.

  8. Example Problem 2 Convert the source below into a Thévenin equivalent. ZLOAD

  9. Example Problem 3 Convert the source below into a Thévenin equivalent and determine the power dissipated by the load.

  10. Review Conjugates • The conjugate of C is written as C*, which has the same real value but the opposite imaginary part:

  11. Maximum power is transferred to the load when RLD = RTh. Review Maximum power transfer theorem

  12. Max Power Transfer in AC Circuits • In AC circuits, max power transfer occurs when load impedance (ZL) is the complex conjugate of the Thévinin equivalent impedance (ZTh). • This means the load has a capacitor if the Thèvenin impedance includes an inductor • XLD cancels out XTH!

  13. Max Power Transfer in AC Circuits • Since RLD=RTH, and the reactances cancel out, the resulting PMAX equation is the same as with DC!

  14. X Max Power Transfer in AC Circuits • #1 Mistake with AC Max Power is not using the REAL value of resistance when calculating Pmax • Transform ZTH into rectangular form to determine RTH

  15. Example Problem 4 Determine the load ZLOAD that will allow maximum power to be delivered to the load the circuit below. Find the power dissipated by the load.

  16. Example Problem 5 Determine the load ZLD that will allow maximum power to be delivered to the load the circuit below. Frequency is 191.15 Hz. Find the maximum power. What will happen to power if the frequency is changed to 95.575?

More Related