internal resistance of a source definition: the resistance within a battery, or other voltage...
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Internal Resistance of a Source
Definition:
The resistance within a battery, or other voltage source, that causes a drop in the source voltage
when there is a current .
Lecture 3
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The battery internal resistance
=
π πΏ=π π‘=π ππβ ( πΌπΏΓπ )= πΌπΏΓπ πΏ
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Maximum Power Transfer Theorem
π=π ππ
π πππ‘
π»ππππππππππππππ ππππππππ πππππππ ππππππππππ :
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π=π ππ
π πππ‘
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π=π ππ
π πππ‘
It is clear that . If the load power calculated for a range of variation of load resistance from 0.1 Ξ© to 30 Ξ©, and plotted as shown in the figure , then this will lead to a certain conclusion.
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This table represents the values of the output power, the load current and load voltage
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This plot shows the load power as a function of load resistance
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This plot shows the variation of load voltage and current with load resistance
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The plotted results shows that the maximum load power occurs when the load resistance equal to the internal resistance. Also, it shows that the variation in power is very steep when . This can be verified due to the steep change in load voltage and load current in the same region. Since:
=Where is the power dissipated inside the source due to its internal resistance, then:
This equation means when , tends to . But in this case the power in the circuit will be very small, as shown in the proceeding slide.
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This plot shows the truth that when , tends to , While the following relation show the reduction in output power at this case.
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ππ =π ππΓ πΌ πΏ
π (W )
π πΏ=π πππ‘=9Ξ©
π πΏπππ₯
π πΏ
π πΏ (Ξ© )π πΏ=π πππ‘=9Ξ©
This leads to the fact that the best operating condition is that, when the load resistance equal to the internal resistance of the source, form the view point of maximum power transfer from source to load.
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New and Renewable Energy Sources
Photovoltaic Panel(PV) Panel
And Wind Energy
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The Solar Energyβ’ The Photovoltaic Panel is no more than an energy transducer. It has an ability
to generate electric energy from solar energy. It is one of the renewable energy sources. It is cheap, clean and available.
β’ The most important property to be considered, is that βit has a non-linear internal resistanceβ. This property is shown in the figures below:
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β’ The V/I characteristics shows that this source has a nonlinear internal resistance as compared with that of the battery. Then its output power has a maximum value at one point only as shown in the P/V characteristics shown above.
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PV Array characteristics at different irradiation levels
Note: Such a source needs special arrangements in order to achieve the maximum power point. This is done by changing the value of the input load resistance continuously in order to follow the source internal resistance.