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Electrical network

technology Maturity 9-11 Next article →

An electrical network is an interconnection of various electrical components. These components include items like batteries, resistors, inductors, and capacitors. It can also be a mathematical model of such an interconnection. A network consists of electrical elements like voltage sources or current sources. One important distinction is between a network and a circuit. An electrical circuit is a specific type of network that forms a closed loop. This loop provides a return path for the electric current. Because of this, all circuits are networks, but not all networks are circuits. A network without a closed loop is often called an open circuit.

Engineers classify these networks in several ways to understand them better. One way is by passivity. An active network contains at least one source that supplies energy indefinitely. Examples of active sources include a battery or a generator. These active elements can inject power or control the current flow. In contrast, a passive network does not contain any active sources. It consists only of passive elements like resistors and capacitors. Another classification is by linearity. Linear networks are easier to analyze because their signals are linearly superimposable. This means engineers can use frequency domain methods, such as Laplace transforms, to find responses.

Another way to look at networks is through the concept of lumpiness. Many designs use lumped elements, such as discrete resistors or capacitors. In a lumped-element model, all the resistance or capacitance is assumed to be located in one place. This is the most common approach used in circuit design. However, this assumption fails at very high frequencies. It also fails in very long circuits, like power transmission lines. In these cases, a significant fraction of a wavelength exists across the component. Engineers must then use a distributed-element model. A design that uses both types is called a semi-lumped design, such as a combline filter.

To understand how electricity moves, engineers apply specific mathematical laws. Ohm's law is one of the most fundamental rules. It states that the voltage across a resistor equals the product of resistance and current.

Ohm's Law with Voltage source TeX
Ohm's Law with Voltage source TeX

Kirchhoff's current law is also essential for any node. It says the sum of all currents entering a node must equal the sum of currents leaving it. Kirchhoff's voltage law focuses on loops within a network. It states that the directed sum of electrical potential differences around a loop must be zero. These laws allow engineers to create simultaneous equations to solve for unknown values.

There are several advanced theorems used to simplify complex networks. Norton's theorem states that any network of sources and resistors is equivalent to a single current source in parallel with one resistor. Similarly, Thévenin's theorem shows a network is equivalent to a single voltage source in series with one resistor. The superposition theorem is used for linear networks with multiple independent sources. It says the total response in a branch is the sum of individual responses from each source. These tools allow engineers to turn a massive, complicated system into a much simpler mathematical model.

Modern electrical engineering relies heavily on computer simulation. Designing a physical prototype can be expensive and risky. Instead, engineers use specialized software to predict how voltages and currents will behave. For analog circuits, they might use a simulator called HSPICE. For more complex numerical analysis, they use software like SPICE or GNUCAP. Some engineers even use symbolic software like SapWin. These programs allow for testing designs without the time or cost of building physical hardware. This process helps ensure the design is safe and functional before it is ever manufactured.

When a computer analyzes a new circuit, it often looks for a steady state solution. This is a state where all nodes follow Kirchhoff's current law. Once this operating point is found, the software can perform small-signal analysis. For non-linear elements, the software uses linearization to create an estimate of voltages and currents. Another method is the piecewise-linear approximation. This method, used by interfaces like PLECS to Simulink, treats the network as a collection of ideal diodes. Every time a diode switches, the configuration of the linear network changes. This allows for highly accurate simulations of complex electronic behavior.

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File:Ohm's Law with Voltage source TeX.svg
Ohm's Law with Voltage source TeX.svg
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