transitoires

Transitoires, or transients, is a term used across multiple disciplines to describe temporary phenomena that occur as a system changes from an initial condition to a final steady state. The plural form transitoires is the French equivalent of the English term transients.

In physics and engineering, a transient is the portion of a system’s response that precedes its long-term, steady behavior. Transients arise after a disturbance such as a switch action, a fault, or a sudden input change, and they fade according to the system’s dynamics. They are typically analyzed in the time domain and may be described by differential equations or, in linear time-invariant systems, by impulse or step responses.

In electrical engineering, transient analysis is common when circuits are powered on, switched, or interrupted. Examples include the charging of a capacitor in an RC circuit, the damping of oscillations in an RLC circuit, and switching surges. Characteristics of interest include rise time, peak time, overshoot, damping, and settling time. In control systems, transients reflect how quickly and smoothly a system reaches its desired output after a disturbance, with metrics such as settling time and overshoot used to assess performance.

Non-electrical contexts include mechanical and thermal systems, where startups, braking, impacts, or rapid temperature changes generate transient states. In signal processing, transients are short-duration events that can carry important information but may also be treated as noise requiring filtering or detection.

Modeling approaches for transients include Laplace transform methods, state-space representations, and numerical simulations. Mitigation techniques involve damping, soft-start mechanisms, snubbers, and appropriate filtering to control transient magnitudes and durations.