1. Maximum Power Transfer
The end of this lesson, students should be able to :
State Maximum transfer theorem
Describe the following ;
The maximum power transfer based on circuit diagram.
The power versus load resistance graph
Determine the load needed for maximum power transfer to a circuit
ET101 ELECTRICAL TECHNOLOGY

2. ET101 ELECTRICAL TECHNOLOGY
DEFINITION OF POWER MAXIMUM TRANSFER
The maximum power transfer theorem is stated
that maximum power is transferred from a source
to a load when the load resistance is equal
To the internal source resistance.
Maximum power is transferred to the load when
RL=RTH
ET101 ELECTRICAL TECHNOLOGY

3. Consider the General Case
A resistive network contains independent and dependent sources.
A load is connected to a pair of terminals labeled a – b.
What value of load resistance permits maximum power delivery to the load?
ET101 ELECTRICAL TECHNOLOGY

4. General Case (continued)
ET101 ELECTRICAL TECHNOLOGY

5. Take the Thevenin equivalent of the circuit

6. Look at the power developed in the load
ECE 201 Circuit Theory I

7. Find the value of Rload that maximizes power
ECE 201 Circuit Theory I

8. The maximum power delivered to the load
ECE 201 Circuit Theory I

9. Example 1 a) Find the value of RL for maximum power transfer to RL.
ECE 201 Circuit Theory I

10. Determine the Thevenin Equivalent
ECE 201 Circuit Theory I

11. ET101 ELECTRICAL TECHNOLOGY
Maximum Power Transfer RTH = RL = 25Ω
ET101 ELECTRICAL TECHNOLOGY

12. Example 1.1 continued
b) Calculate the maximum power that can be delivered to RL.
ECE 201 Circuit Theory I

13. Example 2 continued
What percentage of the power delivered by the 360 V source reaches RL? +
Vab -
Isource
ECE 201 Circuit Theory I

14. Example 2 continued Percentage of source power delivered to the load
ECE 201 Circuit Theory I

15. i. The source in Figure 1 has an internal source resistance
Exercise ;
i. The source in Figure 1 has an internal source resistance
of 75Ω. Determine The load power for each of the
following values of load resistances ;
25Ω
50Ω
75Ω
100Ω
125Ω
Draw a graph showing the load power versus the
load resistance.
RS = 75Ω + -
VS=10V
Figure 1 RL