# Voltage drop

For the calculation, a power factor $cos\varphi$ = 0.9 is assumed. The power factor is the ratio of active power to apparent power. When the waveforms are purely sinusoidal, the power factor is equal to the phase angle $\varphi$ between the current and voltage.

IEC 60364-5-52 in Annex G states that the voltage drop between the origin of an installation and any load point should not be greater than:

• Low voltage installations supplied directly from a public low voltage distribution system: 3% in case of lighting and 5% for other uses
• Low voltage installations supplied from private LV supply: 6% in case of lighting and 8% for other uses

Symbol
$V_{drop}$
Unit
V/(A.m)
Formulae
 $\sqrt{3} \left(R_c \mathrm{cos}\varphi+X_c sin\left(\\arccos\left(\mathrm{cos}\varphi\right)\right)\right)$ three-phase system $2\left(R_c \mathrm{cos}\varphi+X_c sin\left(\\arccos\left(\mathrm{cos}\varphi\right)\right)\right)$ single-/two-phase system AC $2R_c \mathrm{cos}\varphi$ single-/two-phase system DC
Related
$\mathrm{cos}\varphi$
$X_c$