Thévenin Equivalent Circuits

The household power distribution system which includes distribution lines and transformers, can be considered the source network.

Inside the house, various electrical appliances can be represented as load impedances.

Thévenin's theorem simplifies this complex distribution system into a Thévenin equivalent circuit.

Finding the Thévenin equivalent circuit requires knowledge of two parameters: Thévenin voltage and Thévenin impedance.

To understand the process of determining them, consider a simplified RLC circuit connected to a voltage source.

To calculate the Thévenin impedance, replace the voltage source with a short circuit and determine the equivalent impedance of the circuit.

The Thévenin voltage is equal to the open circuit voltage, equivalent to the voltage drop across the parallel branch of the circuit.

Initially, the current flowing through the closed mesh of the circuit is calculated. Then using Ohm's law, the voltage drop across the parallel branch is determined, which gives the Thévenin voltage.

If the circuit has sources operating at different frequencies, the Thévenin equivalent circuit and capacitor and inductor impedances must be determined separately for each frequency.