spenningsfall

Spenningsfall, or voltage drop, describes the reduction in electrical potential between the power source and a point in a circuit where current is taken. It is a key consideration in the design and assessment of electrical installations, affecting device performance and reliability.

Voltage drop occurs mainly due to the resistance and reactance of conductors and components through which current flows. Longer cables, higher currents, poor connections, or high-resistance layouts increase the drop. In alternating current systems, the impedance and the phase relationship between voltage and current also influence the drop.

Calculating voltage drop can be straightforward for direct current: V_drop = I × R, where I is the current and R is the resistance of the conductors between source and load. For alternating current, V_drop = I × Z, where Z is the impedance (a combination of resistance and reactance). Because voltage drop in AC depends on phase angle, the percentage drop is often expressed relative to the nominal supply voltage: percentage drop = (V_drop / V_nominal) × 100%. As an example, 10 A flowing through 2 Ω of conductor yields a 20 V drop, about 8.7% on a 230 V system.

Implications of excessive spenningsfall include dimmed lights, malfunctioning equipment, and reduced efficiency. Many electrical codes set limits for voltage drop, typically a total of around 5% from source to outlet, with tighter limits (about 3%) for sensitive devices.

Mitigation strategies include using larger conductor cross-sections, shortening cable runs, splitting loads with shorter feeders or parallel conductors, applying power factor correction, and using voltage regulators or transformers where appropriate. Ensuring good electrical connections also helps minimize additional losses.