Thevenin Equivalent: Solve DC Power Supply 30V/400mA, 27V/600mA

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SUMMARY

The discussion focuses on finding the Thevenin equivalent circuit for a DC power supply with specified terminal voltages and currents. The power supply delivers 30V at 400mA and 27V at 600mA. The calculated Thevenin resistance (Rth) was determined to be 75 ohms and 30 ohms based on different KVL applications, indicating a misunderstanding of the relationship between load resistance and Thevenin parameters. The conclusion emphasizes that Thevenin voltage and resistance are constants for a given circuit, regardless of the load connected.

PREREQUISITES
  • Understanding of Thevenin's Theorem
  • Knowledge of Kirchhoff's Voltage Law (KVL)
  • Familiarity with DC circuit analysis
  • Basic proficiency in MATLAB for circuit simulations
NEXT STEPS
  • Study Thevenin's Theorem applications in circuit analysis
  • Learn advanced KVL techniques for complex circuits
  • Explore MATLAB for simulating Thevenin equivalents
  • Investigate the effects of varying load resistances on circuit behavior
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in analyzing DC power supply circuits will benefit from this discussion.

sisyphus0321
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Homework Statement


Find the Thev Eq circuit for a DC power supply that has a 30-volt terminal voltage when delivering 400mA and a 27-volt terminal voltage when delivering 600mA.


Homework Equations


KVL: Vs=IsR1+IsR2
Vth=Isc*Rth


The Attempt at a Solution


Assuming that each 3volt step is a 200mA change, than Voc would be 36v. I determined the load resistance by checking both current EQs [6vload/.4A] and [9vload/.6A] and determined the solution of both to be 15ohms. I did a KVL utilizing the 30v and 400mA figures and determined that Rth is 75ohms. I then did a KVL with the other figures and received a 30ohm answer. Where have I strayed?
 
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The Thevenin voltage and Thevenin resistance are fixed for a particular black box and don't change when you hook up different loads to it. The load resistance most certainly changes, but you've basically assumed that they're constant (how else would the first circuit only draw 400 mA while the second draws 600 mA?) while the Thevenin Resistance is changing.
 
As you can see by now MATLABdude, Edward Lawry Norton is my arch nemesis. But I thank you for the help!
 

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