Direct current
ΔU = 2 * I * R * L
Alternating single-phase/Alternating two-phase
ΔU = 2 * I * (R * cosφ + X * sinφ) * L
Alternating three-phase
ΔU = √3 * I * (R * cosφ + X * sinφ) * L
ΔU = Voltage drop (V)
I = Current (A)
R = Resistance (Ω/km)
X = Reactance (Ω/km)
L = Line length (km)
φ = Phase shift between voltage and current
Calculate voltage drop in DC and AC circuits using key electrical parameters.
"Voltage drop is the decrease of electrical potential along the path of a current flowing in an electrical circuit. According to Annex G – IEC 60364–5–52."
Direct Current (DC): Current flows constantly from positive to negative pole. Used in batteries, solar panels, and electronics.
Alternating Current (AC): Current reverses direction and amplitude over time at a constant frequency (e.g., 50 Hz or 60 Hz). Used in power grids and homes.
1. Single-phase: One phase conductor and one neutral.
2. Two-phase: Two phase conductors (rare).
3. Three-phase: Three phase conductors; four-wire includes neutral.
4. Unipolar: One conductor.
5. Bipolar: Two conductors.
6. Tripolar: Three conductors.
7. Quadrupolar: Four conductors.
8. Pentapolar: Five conductors.
9. Multipolar: Two or more conductors.
Permissible operating temperature depending on the conductor insulation material.
70°C (158°F): PVC insulation, PVC-coated mineral insulation, or accessible bare mineral insulation.
90°C (194°F): XLPE, EPR, or HEPR insulation.
105°C (221°F): Bare and non-accessible mineral insulation.
60°C (140°F): Types TW, UF
75°C (167°F): RHW, THHW, THW, THWN, XHHW, USE, ZW
90°C (194°F): TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2
Conductors of the same cross-sectional area, length, and material can be connected in parallel. The maximum permissible current is the sum of the individual-core maximum currents.
Distance between supply point and load (one way), measured in meters or feet. Longer lines result in higher voltage drop.
Material used for the conductor. Common materials include copper (lower resistance) and aluminum (lighter, cheaper).
Defines the number of conductors in the cable:
1. Unipolar: One conductor
2. Bipolar: Two conductors
3. Tripolar: Three conductors
4. Quadrupolar: Four conductors
5. Pentapolar: Five conductors
6. Multipolar: Two or more conductors
Difference in electric potential between two points.
Enter Phase-Neutral voltage for single-phase systems (e.g., 120V).
Enter Phase-Phase voltage for two-phase or three-phase systems (e.g., 208V, 480V).
Power to be considered for determining circuit characteristics, measured in watts (W) or kilowatts (kW). Includes all connected devices.
Ratio of active power to apparent power: cosφ, where φ is the phase angle between voltage and current.
Value ranges from 0 to 1. Ideal = 1 (purely resistive load).
Cross-sectional area of the conductor, measured in mm² or AWG.
Larger size → lower resistance → less voltage drop.
VD = I × R × L
VD (%) = (VD / V) × 100
R = ρ × L / A
1. Designing electrical installations in buildings
2. Sizing wires for long-distance power transmission
3. Troubleshooting dim lights or motor issues
4. Compliance with IEC 60364 and NEC standar ds
5. Industrial plant planning
6. Renewable energy systems (solar, wind)
According to IEC 60364-5-52 and NEC standards, the general recommendation is: voltage drop should not exceed 3% for lighting circuits and 5% for power circuits (outlets, motors, etc.).
For example,
in a 230V single-phase system, the maximum allowable drop for lighting is 230 × 3% = 6.9V, meaning the voltage at the load end should not fall below 223.1V. Exceeding this range may cause dim lights, motor overheating, or equipment failing to start properly.
In DC circuits, voltage drop is determined only by resistance (VD = I × R). However, in AC circuits, besides resistance (R), there is also reactance (X), and a phase difference exists between current and voltage.
Power factor (PF = cosφ) reflects the ratio of active power to total apparent power. The lower the PF, the higher the line current for the same active power, resulting in a larger voltage drop.
For example, for the same 5kW load, the current is about 21.7A at PF=1, but increases to about 27.1A at PF=0.8, causing approximately 25% more voltage drop.
Yes, voltage drop is directly proportional to line length (VD = I × R × L). The longer the line, the higher the resistance and the greater the drop. There are three main ways to reduce voltage drop:
① Increase the conductor cross-sectional area (thicker wire means lower resistance);
② Increase the system voltage (lower current for the same power);
③ Use parallel conductors (multiple conductors of the same specification in parallel increase the equivalent cross-sectional area). Proper wire sizing is especially important in solar power systems and long-distance power transmission.
Copper has a significantly lower resistivity (approximately 1.68×10⁻⁸ Ω·m) than aluminum (approximately 2.82×10⁻⁸ Ω·m), so for the same cross-sectional area and length, the voltage drop of an aluminum conductor is about 68% higher than that of a copper conductor.
In other words, to achieve the same voltage drop performance, aluminum wire needs to be one size larger than copper wire (e.g., if copper uses 4mm², aluminum would need 6mm² or 10mm²). Although aluminum wire is lighter and cheaper, copper wire is the more reliable choice in applications where voltage drop requirements are strict.
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