Lastkretsen

Lastkretsen is a term used in electrical engineering and building installations to describe the final stage of an electrical distribution system—the part that delivers power to the actual consumers or loads. It refers to the circuits and conductors that run from the distribution board to outlets, fittings, lights, and fixed appliances. The lastkretsen is distinguished from higher-level distribution lines and feeders that connect to transformers and main switchgear, as it directly serves end devices and loads.

In practice, the lastkretsen comprises branch circuits that include protective devices such as circuit breakers or fuses, and often residual-current devices (RCDs). Conductors are sized for the expected load, with attention to voltage drop, heat dissipation, and the distinction between continuous and non-continuous loads. Common examples are lighting circuits and socket outlets, but the term also covers circuits feeding fixed appliances. Electrical calculations for the lastkretsen rely on established relationships such as Ohm’s law and electrical power formulas (P = VI, P = I^2R).

Safety and standards are central to the concept. Building codes and electrical installation standards govern how the lastkretsen is planned, installed, and tested, including requirements for protection against overloads, fault currents, proper earthing, labeling, and accessibility. In many jurisdictions, installations must ensure that the lastkretsen remains independent from control or signaling circuits to minimize interference and maintain reliability.

In industrial contexts, the notion of lastkretsen can also refer to the final control or actuation circuit that feeds devices such as actuators, sensors, or indicators, representing the last leg of a control chain from power source to end effectors.