# transient

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## transient

Physics a brief change in the state of a system, such as a sudden short-lived oscillation in the current flowing through a circuit
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Transient

(or transient phenomenon). A transient in an electric circuit is a phenomenon that occurs during a transition from one circuit condition to another that differs from the initial condition in the amplitude, phase, shape, or frequency of the voltage acting in the circuit, the values of the parameters, or the configuration of the circuit. Transients occur chiefly when circuit elements are switched into or out of the circuit. The transients arise because the current flowing through an inductance and the voltage across a capacitance cannot be altered abruptly—that is, the energy of the electric and magnetic fields in the circuit’s capacitive and inductive elements cannot be changed instantaneously.

Theoretically speaking, a transient continues for an indefinite period because the voltage and current in an electric circuit after the closing or opening of a switch approach their final (steady-state) values asymptotically. In electrical engineering, however, a transient is considered to be ended when the voltage and current reach values differing from the steady-state values by 5 to 10 percent, a condition that occurs within a comparatively short finite interval of time. An electric circuit that is characterized by constant or periodically varying currents and voltages is said to be in a steady-state condition.

A simple example of a transient is the charging of a capacitor C (Figure 1) from a DC source (a storage battery) having an electromotive force (emf) E and an internal resistance r through a resistor R, which limits the current in the circuit. If the switch is closed at the time t = 0, the current in the circuit decreases according to an exponential law and approaches zero. Simultaneously, the voltage increases and approaches asymptotically the value of the source emf. The rate of change of the voltage and the current depend on the capacitance of the capacitor and the resistance in the circuit: the larger the capacitance and resistance, the longer the duration of the charging process. After a time interval τ = (R + r)C, called the time constant for the charging of the capacitor, the voltage across the capacitor’s plates attains the value uc = 0.6327, and the current i reaches 0.37I0, where I0 is the initial current. I0 is equal to the ratio of the emf and the resistance in the circuit. After a time interval of 5τ;, UC > 0.99E and i < 0.01I0; with an error of less than 1 percent, the transient can be regarded as having ended. During the transient, the energy of the capacitor’s electric field is increased from zero to Wc = CE2/2.

During a transient, in individual parts of a circuit there may occur voltage surges and overcurrents—that is, voltages and currents substantially greater than the steady-state voltages and currents. When equipment is not selected properly, the voltage surges can result in the breakdown of insulation in, for example, capacitors, transformers, and electrical machines. Overcurrents can cause the actuation of protective devices and the disconnection of equipment; they can burn out instruments, burn contacts, and cause mechanical damage to windings as a result of electro-dynamic stresses. Transients play an exceptionally important role in automatic control systems, pulse engineering, computer technology, measurement technology, electronics, radio engineering, and power engineering.

### REFERENCES

Neiman, L. R., and K. S. Demirchian. Teoreticheskie osnovy elektrotekhniki, vol. 1. Leningrad, 1967.
Ginzburg, S. G. Metody resheniia zadach po perekhodnym protsessam ν elektricheskikh tsepiakh, 3rd ed. Moscow, 1967.
Venikov, V. A. Perekhodnye elektromekhanicheskie protsessy ν elektricheskikh sistemakh. Moscow, 1970.
Teoreticheskie osnovy elektrotekhniki, part 1. Moscow, 1972.
Bessonov, L. A. Teoreticheskie osnovy elektrotekhniki. Moscow, 1973.

B. IA. ZHUKHOVITSKII

## transient

[′tranch·ənt]
(physics)
A pulse, damped oscillation, or other temporary phenomenon occurring in a system prior to reaching a steady-state condition.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## transient

1. <electronics> A sudden, brief increase in current or voltage in a circuit that can damage sensitive components and instruments.

## transient

A malfunction that occurs at random intervals and lasts for a short duration such as a spike or surge in a power line or a memory cell that intermittently fails. See spike and power surge.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in periodicals archive ?
So the endpoint of transients [P.sub.E] can be defined as the point that after it nearly all values are smaller than 1/[L.sub.T], which means that all values in the energy trajectory after [P.sub.E]-th slide are stable.
Previous analyses had shown no overlap of AT1 or GOA transients with those in the Aleutian Islands (Durban et al., 2010).
A group of astronomers recently detected a mysterious transient - a bright flash of light that looks like a result of a stellar explosion but carries very different characteristics.
Cyclic transients in the circuits of electric discharge installations taking into account the influence of magnitude and rate of discharge currents rise on resistance of electric spark load.
The study of transients of lines usually tells us about the stress on the different components.[6] Single phase switching is used in 765 KV transmission network because all station equipment (circuit breakers and shunt reactors) used in this network are constructed as single phase units which reduce the system instabilities caused by faults and related switching operations[9].
The ramp-up engine dynamometer test provides a glimpse of how engine operation is altered during rapid transients. Figure 5 shows two separate transient tests covering the same load and speed range, but at two different transition periods of 30 seconds and 0.1 second ramp-ups.
Action potential- (AP-) induced [Ca.sup.2+] transients were triggered using a brief electrical field stimulus.
According to the author [1] the overall duration of the diesel shunting locomotive in a transient mode can reach 20-40% of the total operating time.
Since we observed spontaneous calcium transients in a large fraction of the differentiating cells, it was of interest to further explore the development of calcium-regulating mechanisms by comparing the mechanisms in differentiating cells with mechanisms operating in proliferating cells.
ProTek Devices has introduced two new circuit protection components that shield a variety of networking, mobile and other computing applications from the destructive effects of electrical transients, the company said.
COTTAGE GROVE - An abandoned home occupied by transients caught fire Monday afternoon, causing heavy damage and making the structure uninhabitable, fire officials said.

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