Transients in electrical circuits

Considering transients in electrical circuits, it is necessary to note the fact that such phenomena are quite natural and to some extent predictable. Moreover, each person faces their manifestation in their daily life. For example, in a heating element included in the network (electric heater stove, oil heater), the temperature rises not indefinitely but up to a certain value, depending on a number of factors: such as ambient temperature, humidity level, wire characteristics, etc. Accordingly, Up to some steady-state value, and not to absolute zero. In other words, all physical phenomena can be conditionally divided into transitional and established phenomena . The first is a change between the initial and final established.

What are transients in electrical circuits? When analyzing any circuit, two possible operating modes must be considered: steady-state and transient. The first is characterized by the instantaneous values of the alternating current and voltage that are repeated per unit time in all parts of the circuit. Transients in electrical circuits are easier to understand: when such changes stop, then we can talk about the onset of a steady-state regime. The consequence is the following: a state in which there are no changes, theoretically, can last indefinitely.

Transients in linear electric circuits are familiar to everyone. For sure, everyone happened that after the click of the home switch the lamp burned out or even the glass bulb itself flew to the fragments. Moreover, this can happen both with budget lamps, and with expensive branded ones. In this "transient processes in electric circuits " are guilty . In this case, that click of the switch caused changes, initiated a transient process, called switching (i.e., switching). In fact, the reasons can be different: changing the parameters of the power source, in particular short circuit, external influences (magnetic field, temperature), etc. Direct calculation of the voltage and current changing per unit time is possible by means of differential equations and integral calculation. In the formulas, the number of derivatives directly depends on the elements of the chain itself.

Since usually the duration of the transient process is calculated not even by seconds, but by the hundredth and thousandths of a second, sometimes the question arises of the expediency of calculations. Indeed, what can happen in such a short time? Alas, this is only partly true, and practice shows that quite a lot. For example, the power contacts of the starters are always designed for a much larger current than the rated current. In addition, the contacts are often closed by arc chutes (gratings). This is explained by the fact that at the moment of commutation (switching on / breaking of the circuit) the current increases tens of times, and to solve the possible consequences, these solutions are applied.

Consider transients in rc circuits. For example, let's take a circuit consisting of a power source, a pair of resistors (R1 and R2), a capacitor (C) and a voltmeter (V) connected in parallel. If the capacitor used has a capacity of tens of microfarads, and the resistance R1 and R2 - a couple of hundred kilo, respectively, when the source is turned on, the voltmeter will not immediately indicate the effective value of the voltage, but gradually deviate from zero. This transient process is due to the accumulation of charge in the tank. Accordingly, the steady-state regime occurs at the moment when the consumption of the reactive component ceases.