🚀 Cable Ampacity Calculator & Simulator
- Select System Voltage and Phase: Choose your power transmission environment, such as single-phase 220V or three-phase 380V.
- Define Load Capacity and Transmission Distance: Use the sliders to set the required current (Amperes) and the cable installation distance (m) from the power source to the load.
- Configure Limits and Wiring Materials: Select the cable conductor material (Copper Cu, Aluminum Al) and the installation method (exposed tray, conduit, or direct burial).
- Analyze Real-Time Cable Conditions: Monitor the calculated optimal nominal size (mm²), thermal load factors due to excessive charge density, and real-time voltage drop percentages on the measurement display.
📚 Detailed Conductor Cross-Sectional Area Calculation & Voltage Drop Formulas (Interior Wiring Regulations / KEC) ▼
1. Three Key Engineering Factors for Cable Sizing
When selecting conductors for a safe power supply, the cable must satisfy all three core evaluation criteria in accordance with the Korea Electro-technical Code (KEC):
- Ampacity (Allowable Current): The safe limit of current that can continuously flow through a conductor without exceeding the maximum allowable temperature of its insulation (e.g., 90°C for XLPE). Correction factors are applied based on the installation environment (enclosure, ambient temperature).
- Voltage Drop: A phenomenon where the voltage at the load end decreases due to the resistance of the conductor itself as the transmission line length increases. Since this can cause equipment malfunction and reduced efficiency, it must typically be limited to within 3% to 5%.
- Mechanical Strength and Short-Circuit Current: The cable must have the thermal and mechanical capacity to withstand instantaneous short-circuit currents during a fault.
2. Allowable Voltage Drop and Cross-Sectional Area (A) Calculation Formulas
The standard formulas for allowable current and voltage drop in low-voltage wiring, as used in the interior wiring regulations, are summarized as follows:
① DC and Single-Phase 2-Wire Line Voltage Drop Formula:
e = (35.6 × L × I) / (1000 × A) [V]
② Three-Phase 3-Wire Line Voltage Drop Formula:
e = (30.8 × L × I) / (1000 × A) [V]
Where L is the one-way line length (m), I is the load current (A), and A is the wire cross-sectional area (mm²). Solving these equations for the conductor cross-sectional area A yields the minimum required cable size as follows:
A_req = (30.8 × L × I) / (1000 × e_allow) [mm²] (Three-Phase Basis)
3. Corrections Based on Installation Environment and Conductor Resistivity
The safe current capacity of a cable is heavily dependent on the specific resistivity of the conductor (ρ) and the geometric conditions of how the conductor dissipates heat to the surroundings.
- Copper Conductor: Featuring excellent electrical conductivity (resistivity of
1/58) and high durability, it is selected for most building and industrial facilities. - Aluminum Conductor: Although its conductivity is lower at approximately 61% of copper (resistivity of
1/35), it is lightweight and cost-effective, making it the choice for large-scale, high-voltage utility transmission and distribution lines. However, for a given current level, a nominal size 1 to 2 steps larger than copper must be selected to ensure safety.