The Thevenin equivalent is useful in finding the
maximum power a linear circuit can deliver to a load. We assume that we can
adjust the load resistance RL .
In this photo, if the entire circuit is replaced by its Thevenin
equivalent except for the load, as shown, the power delivered to the load is the equation we write on the whiteboard. Then we make a sketch of the power as a function of load
resistance.
In this photo, to find the point of
maximum power transfer, we differentiate p in the equation above with
respect to RL and set the result equal to zero. And in the end we find that Rth=RL.
Maximum
power is transferred to the load when the load resistance equals the
Thevenin
resistance as seen from the load (RL = RTh ).
Then we did an example about max power.
In this photo,we obtain
the Thevenin equivalent at terminals a-b and Find RL for maximum power
In this photo, we did an example to find the Rth=0.0527 ohms Pmax=732W
Lab: Maximum Power Transfer
Purpose: to attempt to maximize power transfer to a load by modifying the source circuit. Also, we will see that this approach is inappropriate; the maximum power transfer theorem does not apply in reverse.
The professor didn't let us do the pre-lab, but do the lab instead.
In this photo, we use Rs= 4.6 kohms.
In this photo, we change the value of RL and make a table about Vout and the power and we find that max power is 1.33*10^-3 when RL=5K ohms, which is same as Rs=4.7k ohms.
Then we learn about source modeling
In this photo, we did an example to calculate the source voltage v s and internal resistance R s
. Then we determine the voltage when an 8-Ohm load is connected to the source.
Summary:
Today, we learn maximum power transform. It is important to transfer maximum power to the load. In order to do that, the load resistance should equal the Thevenin resistance. We also learn that souce modeling, power sources contain an internal resistance and how to calculate the resistance.
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