Cable Cross‑Sections & Current Capacity

Ampacity Tables for Copper and Aluminum Conductors

Correct cable selection is one of the most important steps in designing and installing industrial electrical systems. Choosing the proper cross‑section ensures safe operation, prevents overheating, reduces voltage drop and increases the lifetime of motors, feeders and control circuits. This section provides practical ampacity tables for copper (Cu) and aluminum (Al) conductors, based on typical installation conditions used in industrial environments. The values are suitable for panel builders, electricians and technicians working with motors, distribution boards and machine wiring.

Cable ampacity depends on several factors: conductor material, insulation type, installation method, ambient temperature and cable grouping. The tables below represent standard reference values commonly used in European industry. For long cable runs or special conditions, voltage drop and derating factors must be considered.

1 – Copper Cable Ampacity

Copper Cable Cross‑Sections & Current Capacity
Cross‑Section (mm²) Max Current (A) Typical Use
1.5 16–18 Lighting, small loads, control circuits
2.5 20–25 Sockets, small motors, auxiliary circuits
4 25–32 Motors up to 4–5.5 kW, feeders
6 32–40 Motors 5.5–7.5 kW, small distribution
10 45–63 Motors 7.5–11 kW, main feeders
16 63–85 Motors 11–15 kW, sub‑distribution
25 85–110 Motors 18.5–22 kW, long feeders
35 110–135 Heavy loads, industrial feeders
50 135–170 Large motors, main supply lines
70 170–215 High‑power feeders
95 215–260 Industrial distribution
120 260–300 Heavy industrial loads

2 – Aluminum Cable Ampacity

Aluminum Cable Cross‑Sections & Current Capacity
Cross‑Section (mm²) Max Current (A) Typical Use
16 50–60 Small feeders, light industrial loads
25 65–75 Medium feeders
35 80–95 Motors 11–15 kW (long runs)
50 95–115 Industrial feeders
70 120–145 Main supply lines
95 145–175 Heavy industrial feeders
120 175–200 High‑power distribution
150 200–230 Large industrial installations
185 230–260 High‑capacity feeders
240 260–300 Main industrial supply

3 – Recommended Motor Cable Sizes 

Recommended Cable Sizes for Motors (400 V)
Motor Power (kW) Rated Current (A) Recommended Cable (Cu)
0.75 2 1.5 mm²
1.1 3 1.5 mm²
1.5 4 1.5 mm²
2.2 5 1.5–2.5 mm²
3 6 2.5 mm²
4 8 2.5 mm²
5.5 11 2.5–4 mm²
7.5 15 4 mm²
11 21 4–6 mm²
15 29 6 mm²
18.5 37 10 mm²
22 42 10–16 mm²
30 58 16 mm²

4. Notes and Practical Recommendations

• Copper cables carry more current than aluminum for the same cross‑section.

• For long distances, always calculate voltage drop.

• Ambient temperature above 30°C requires derating.

• Grouped cables reduce ampacity due to heat accumulation.

• Motors with heavy starting loads may require larger cables.

• Always follow local electrical standards and manufacturer recommendations.