EE302: Electrical Network Analysis - Topic 3: Transients

Flashcards covering the key concepts of transients in AC and DC circuits.

Transients

Temporary changes in a system's behaviour before it settles into a steady state.

Transient

Variation of a system quantity (current, flux velocity) in a physical system following a disturbance, persisting until the system settles to a new energy level/state.

Transient Currents

Are related to changes in stored energy in inductors and capacitors, not in resistors.

Initiation Transients

Transients produced when originally dead circuits are energized.

Subsidence Transients

Transients produced when an energized circuit is rapidly de-energized and finally reaches zero voltage or current, such as in short-circuiting an R-L circuit.

Transition Transients

Transients due to sudden but energetic changes from one energy state to another.

p = Ri^2

The rate energy is dissipated in an inductive circuit with resistance.

Current in Steady State R-L Circuit

The current in a series R-L circuit in steady state depends on the applied voltage and resistance, and is independent of inductance.

Back EMF

Opposition to current change in an inductive coil (Lenz's Law).

Time Constant

Time taken for current to reach 63.2% of its final value or the time to reach final current if the initial rate of change is maintained.

Resultant Current in AC R-L Circuit

sum of steady-state current and transient current

Size of Transient Current in AC R-L Circuit

Depends on the angle at which the circuit is closed in the AC cycle.

Energy Stored in a Magnetic Field

L * I^2 / 2

Current When a Charged R-C Circuit is Short-Circuited

Transient discharge following a short circuit

Voltage Drop Across Resistor in R-C Circuit

The Voltage across resistor= Ee^(-t/RC)

Behavior of transient current In a DC R-C circuit

Current is maximum initially reducing to zero in steady-state.

reciprocal of time constant

Damping coefficient.

Graph resultant values of Voltage and current voltage of R-C (AC) circuit

Transient are OA and is made up of steady-state current OC and transient current, OB

Double-Energy Transients

Transient current produced due to redistribution of electromagnetic and electrostatic energies; may be unidirectional or decaying oscillatory.

Transients in Loss-Free RLC Circuit

Transient current is sinusoidal wave of constant peak value and frequency.

Transients in Low-Loss RLC Circuit

Transient current is damped oscillatory.

Transients in High-Loss RLC Circuit

Transient current is non-oscillatory.

Transients in Critically Damped RLC Circuit

Current is reduced to almost zero in shortest possible time.

Laplace Transformation

A method to analyze transients, providing a direct solution to differential equations by transforming functions from the time domain to the complex frequency domain.