NORTON’S THEOREM

Rabert T
03/09/2024

Norton’s Theorem is a principle in electrical engineering that allows the complex impedance of an electric circuit to be reduced to a single equivalent impedance. It states that any linear, two-terminal electrical network can be represented by an equivalent circuit consisting of a single current source in parallel with a single impedance. The current of the source is the short-circuit current of the network, and the impedance is the impedance seen looking into the circuit with the current source removed and the terminals open-circuited. Norton’s Theorem is named after the American engineer E. L. Norton, who first proposed it in the early 20th century.

STATEMENT OF NORTON’S THEOREM:

Any linear, active, bidirectional dc network with a number of voltage sources and/or current sources with resistances can be substituted by a simple equivalent circuit with a single current source (IN) in parallel with a single resistance (RN).

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Where,

(IN) is the Norton’s equivalent current across terminals a-b.

(RN) is the Norton’s equivalent resistance across terminals a-b.

Similar to Thevenin’s theorem, except that the voltage source is gradually replaced by a current source

Find the Thevenin equivalent circuit first, then convert it to an equivalent current source.

The Norton equivalent resistance:

RN =RTH

The Norton equivalent current:

IN = VTH/RTH

Idenotes the current flowing in the short circuit connected across the terminals where the Norton equivalent circuit is required.

The Norton equivalent circuit is a useful tool for analyzing and designing electrical circuits because it allows the circuit to be represented by a single, simplified model. This makes it much easier to understand the behavior of the circuit and to calculate its response to different input signals.

To determine the Norton equivalent of a circuit, the following steps can be followed:

  • Remove all independent sources from the circuit and open the terminals.

  • Determine the impedance looking into the terminals with the sources removed. This is the Norton impedance.

  • Restore the sources to the circuit and determine the short-circuit current at the terminals. This is the Norton current.

  • The Norton equivalent circuit is a current source with a value equal to the Norton current in parallel with an impedance equal to the Norton impedance.

  • Norton’s Theorem is only applicable to linear, two-terminal networks. It is not applicable to nonlinear circuits or circuits with more than two terminals.

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Rabert T

As an electrical engineer with 5 years of experience, I focus on transformer and circuit breaker reliability in 110/33-11kV and 33/11kV substations. I am a professional electrical engineer with experience in transformer service and maintenance.

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