Motor Cable Size Chart: Cross-Section and Length by Motor Power
Permitted cable lengths at 3% voltage drop by motor power, voltage and starting method, with direct-on-line and star-delta charts and a selector tool.
A motor cable size chart is used to select the cross-section of the cable feeding an electric motor according to motor power, supply voltage, starting method and cable length. On long runs the cable resistance causes a voltage drop; too low a voltage at the motor terminals leads to difficult starting, overcurrent and overheating.
The charts below give the maximum permitted cable length in metres for each cross-section, based on a 3% voltage drop and an ambient temperature of 25 °C. Direct-on-line values for 220 V (single-phase) and 380 V (three-phase), and star-delta values for 380 V, are given in separate tables.
How to Use the Chart
- Determine the motor power (kW or HP) and starting method.
- Find the motor power row in the relevant table.
- In that row, choose the cross-section of the first column whose value is equal to or greater than your cable length.
Example: A 15 kW (20 HP) motor, direct-on-line at 380 V, is fed by a 100 m cable. In the 15 kW row the maximum length is 80 m for 6 mm² and 130 m for 10 mm². For 100 m, a 3 × 10 mm² cable is selected.
Cable Size Selector
The tool selects the motor rating equal to or next above the power entered and finds the smallest cross-section whose tabulated length covers your cable run. Current-carrying capacity and protective devices must be checked separately.Cable Chart 1 – Direct-on-Line, 220 V (Single-Phase)
| HP | kW | Cable cross-section 3 × … mm² – maximum length (m) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1.5 | 2.5 | 4 | 6 | 10 | 16 | 25 | 35 | 50 | 70 | 95 | 120 | 150 | ||
| 0.5 | 0.37 | 80 | 130 | – | – | – | – | – | – | – | – | – | – | – |
| 0.75 | 0.55 | 55 | 90 | 140 | – | – | – | – | – | – | – | – | – | – |
| 1 | 0.75 | 40 | 80 | 105 | 160 | – | – | – | – | – | – | – | – | – |
| 1.5 | 1.1 | 30 | 50 | 75 | 115 | 190 | – | – | – | – | – | – | – | – |
| 2 | 1.5 | 20 | 35 | 60 | 90 | 145 | 235 | – | – | – | – | – | – | – |
| 3 | 2.2 | – | 30 | 50 | 70 | 120 | 185 | – | – | – | – | – | – | – |
Cable Chart 2 – Direct-on-Line, 380 V (Three-Phase)
| HP | kW | Cable cross-section 3 × … mm² – maximum length (m) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1.5 | 2.5 | 4 | 6 | 10 | 16 | 25 | 35 | 50 | 70 | 95 | 120 | 150 | ||
| 1 | 0.75 | 230 | – | – | – | – | – | – | – | – | – | – | – | – |
| 1.5 | 1.1 | 180 | 235 | – | – | – | – | – | – | – | – | – | – | – |
| 2 | 1.5 | 135 | 225 | 360 | – | – | – | – | – | – | – | – | – | – |
| 3 | 2.2 | – | 190 | 300 | 460 | – | – | – | – | – | – | – | – | – |
| 4 | 3 | – | 150 | 240 | 360 | – | – | – | – | – | – | – | – | – |
| 5.5 | 4 | – | 110 | 170 | 260 | 450 | – | – | – | – | – | – | – | – |
| 7.5 | 5.5 | – | 80 | 150 | 190 | 340 | 540 | – | – | – | – | – | – | – |
| 10 | 7.5 | – | 60 | 100 | 150 | 250 | 410 | – | – | – | – | – | – | – |
| 12.5 | 9.2 | – | 50 | 80 | 120 | 205 | 330 | 510 | – | – | – | – | – | – |
| 15 | 11 | – | – | 60 | 100 | 170 | 280 | 440 | – | – | – | – | – | – |
| 17.5 | 13 | – | – | – | 90 | 150 | 245 | 385 | – | – | – | – | – | – |
| 20 | 15 | – | – | – | 80 | 130 | 210 | 330 | 460 | 660 | – | – | – | – |
| 25 | 18.5 | – | – | – | – | 100 | 170 | 260 | 370 | 530 | – | – | – | – |
| 30 | 22 | – | – | – | – | 90 | 140 | 220 | 310 | 440 | – | – | – | – |
| 35 | 26 | – | – | – | – | – | 120 | 190 | 270 | 380 | 540 | – | – | – |
| 40 | 30 | – | – | – | – | – | 100 | 170 | 230 | 330 | 460 | – | – | – |
| 50 | 37 | – | – | – | – | – | – | 130 | 190 | 270 | 380 | 520 | – | – |
| 60 | 45 | – | – | – | – | – | – | 110 | 160 | 230 | 320 | 440 | 550 | – |
| 70 | 52 | – | – | – | – | – | – | – | 140 | 200 | 280 | 385 | 480 | – |
| 75 | 55 | – | – | – | – | – | – | – | 120 | 170 | 240 | 330 | 410 | 530 |
| 80 | 59 | – | – | – | – | – | – | – | 115 | 160 | 230 | 310 | 390 | 500 |
| 90 | 66 | – | – | – | – | – | – | – | 110 | 150 | 220 | 290 | 370 | 470 |
| 100 | 75 | – | – | – | – | – | – | – | 96 | 140 | 190 | 270 | 350 | 425 |
| 110 | 81 | – | – | – | – | – | – | – | – | 125 | 175 | 245 | 300 | 380 |
| 125 | 92 | – | – | – | – | – | – | – | – | 110 | 160 | 220 | 275 | 340 |
| 150 | 110 | – | – | – | – | – | – | – | – | – | 130 | 180 | 220 | 290 |
| 180 | 132 | – | – | – | – | – | – | – | – | – | – | 150 | 190 | 240 |
| 200 | 150 | – | – | – | – | – | – | – | – | – | – | 130 | 170 | 190 |
| 225 | 165 | – | – | – | – | – | – | – | – | – | – | 125 | 150 | 190 |
| 250 | 185 | – | – | – | – | – | – | – | – | – | – | – | – | 170 |
| 275 | 200 | – | – | – | – | – | – | – | – | – | – | – | – | 160 |
Cable Chart 3 – Star-Delta, 380 V
| HP | kW | Cable cross-section 3 × … mm² – maximum length (m) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1.5 | 2.5 | 4 | 6 | 10 | 16 | 25 | 35 | 50 | 70 | 95 | 120 | 150 | ||
| 4 | 3 | 140 | 230 | 370 | – | – | – | – | – | – | – | – | – | – |
| 5.5 | 4 | 100 | 170 | 270 | 400 | – | – | – | – | – | – | – | – | – |
| 7.5 | 5.5 | 70 | 120 | 200 | 300 | 500 | – | – | – | – | – | – | – | – |
| 10 | 7.5 | 57 | 90 | 150 | 220 | 380 | – | – | – | – | – | – | – | – |
| 12.5 | 9.2 | 46 | 70 | 120 | 180 | 310 | 490 | – | – | – | – | – | – | – |
| 15 | 11 | 39 | 60 | 100 | 150 | 260 | 400 | – | – | – | – | – | – | – |
| 17.5 | 13 | – | 55 | 90 | 130 | 230 | 355 | – | – | – | – | – | – | – |
| 20 | 15 | – | 50 | 80 | 110 | 200 | 310 | 490 | – | – | – | – | – | – |
| 25 | 18.5 | – | – | 60 | 90 | 160 | 250 | 400 | 560 | – | – | – | – | – |
| 30 | 22 | – | – | 50 | 70 | 130 | 210 | 340 | 470 | – | – | – | – | – |
| 35 | 26 | – | – | 46 | 68 | 110 | 180 | 290 | 410 | – | – | – | – | – |
| 40 | 30 | – | – | – | 60 | 100 | 160 | 250 | 360 | 500 | – | – | – | – |
| 50 | 37 | – | – | – | 40 | 80 | 130 | 200 | 290 | 410 | – | – | – | – |
| 60 | 45 | – | – | – | – | 70 | 110 | 170 | 240 | 350 | 480 | – | – | – |
| 70 | 52 | – | – | – | – | – | 95 | 150 | 210 | 305 | 420 | – | – | – |
| 75 | 55 | – | – | – | – | – | 80 | 130 | 180 | 260 | 360 | 500 | – | – |
| 80 | 59 | – | – | – | – | – | – | 120 | 170 | 245 | 340 | 475 | – | – |
| 90 | 66 | – | – | – | – | – | – | 110 | 160 | 230 | 320 | 450 | 520 | – |
| 100 | 75 | – | – | – | – | – | – | 100 | 150 | 200 | 290 | 380 | 440 | 540 |
| 110 | 81 | – | – | – | – | – | – | – | 135 | 185 | 260 | 340 | 405 | 495 |
| 125 | 92 | – | – | – | – | – | – | – | 120 | 170 | 230 | 300 | 370 | 450 |
| 150 | 110 | – | – | – | – | – | – | – | 100 | 140 | 200 | 250 | 300 | 370 |
| 180 | 132 | – | – | – | – | – | – | – | – | 120 | 165 | 210 | 260 | 310 |
| 200 | 150 | – | – | – | – | – | – | – | – | – | 150 | 190 | 230 | 280 |
| 225 | 165 | – | – | – | – | – | – | – | – | – | 130 | 170 | 200 | 240 |
| 250 | 185 | – | – | – | – | – | – | – | – | – | 125 | 160 | 190 | 230 |
| 275 | 200 | – | – | – | – | – | – | – | – | – | – | 140 | 170 | 200 |
Values are maximum lengths (m) for copper conductor cables, calculated for a 3% voltage drop at 25 °C. A dash (“–”) means the section is not suitable for that power or no value is given.
Frequently Asked Questions
Is cable size selected on voltage drop alone?
No. Besides voltage drop, the current-carrying capacity (depending on installation method and ambient temperature), short-circuit withstand and coordination with protective devices must also be checked. The chart gives a preliminary selection with respect to length.
What if the ambient temperature is higher?
Conductor resistance rises with temperature, which reduces the permitted length for the same section and lowers current-carrying capacity. In hot environments the next larger section may be needed.
Can the chart be used for submersible pumps?
The chart is for general motor supplies. For submersible pump motors, use the manufacturer’s cable tables and permitted voltage drop.
Conclusion
The correct cable cross-section is essential for safe starting, efficient operation and long motor life. With the charts and selector you can quickly determine the section from motor power and cable length. For electric motors and pump accessories, see our pump accessories and spare parts product group.
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