Size single phase motor conductors from inputs. Review current, derating, distance, and voltage drop instantly. Pick practical wire sizes for safer reliable motor service.
| Motor | Voltage | PF | Efficiency | Length | Material | Suggested Size |
|---|---|---|---|---|---|---|
| 2 hp | 230 V | 0.85 | 82% | 30 m | Copper | 4.0 mm² |
| 5 hp | 230 V | 0.88 | 86% | 45 m | Copper | 10.0 mm² |
| 3 kW | 230 V | 0.90 | 88% | 60 m | Aluminum | 16.0 mm² |
1. Output power conversion: Motor output watts = hp × 746, or kW × 1000.
2. Input power: Input watts = output watts ÷ efficiency.
3. Running current: Current = input watts ÷ (voltage × power factor).
4. Design current: Design current = running current × design factor.
5. Voltage drop: Drop = 2 × length × current × resistance per meter.
6. Theoretical area: Area = (2 × resistivity × length × current) ÷ allowable drop volts.
7. Corrected ampacity: Corrected ampacity = base ampacity × temperature factor × grouping factor.
8. Final selection: Choose the first standard wire size that passes both ampacity and voltage drop limits.
Single phase motor wire size affects safety, heat, and performance. A small wire can overheat. A long cable can also create excess voltage drop. Motors dislike low voltage. They may start slowly, run hotter, and fail early.
A motor draws current from output power, voltage, efficiency, and power factor. Lower efficiency means higher current. Lower power factor also raises current. This calculator converts hp or kW into current first. That gives the base electrical load for the circuit.
Wire size should not be chosen from motor current alone. Real installations need margin. The design factor adds that margin. It helps when loads are continuous or conditions are uncertain. This approach supports safer conductor selection before local code checks are applied.
Distance matters in motor circuits. Every conductor has resistance. Resistance causes voltage drop. On a short run, the drop may be minor. On a long run, the motor may receive much less voltage. That can reduce torque and increase heating. This page checks the drop for each standard cable size.
Conductor ampacity changes with ambient temperature and cable grouping. Hot spaces reduce current capacity. Bundled conductors also reduce cooling. That is why the calculator applies temperature and grouping factors. A wire that looks large enough on paper may become too small after derating.
Copper has lower resistance and usually higher ampacity for the same size. Aluminum can still be useful, but it often needs a larger cross section. This tool compares both materials with separate resistance and ampacity values. That gives a more practical result for motor branch circuits.
This calculator is made for planning and estimating. It helps electricians, engineers, technicians, and students review motor conductor sizing fast. Still, final selection should follow your local electrical code, insulation type, installation method, short circuit protection, and motor manufacturer guidance.
No. Breaker size and conductor size are related, but they are not identical. The breaker protects the circuit. The wire must also satisfy ampacity and voltage drop requirements.
Those values affect real current draw. A motor with lower efficiency or lower power factor needs more current for the same output power.
Longer runs increase resistance. More resistance causes more voltage drop. A larger conductor reduces that drop and supports better motor performance.
Copper usually carries more current per size and has lower resistance. Aluminum can still work well, but it often needs a larger cross section.
Usually the conductor is sized from running conditions, design margin, and code rules. Starting current is still important for breaker choice and motor starting performance.
It reduces usable ampacity when conductors are grouped together. Bundled wires cannot cool as well, so safe current capacity falls.
Use it for planning and checking. Final approval should always follow local electrical code, site conditions, and the authority having jurisdiction.
That value comes from resistivity and allowable voltage drop. It helps explain the calculation, but the final recommendation still uses practical standard wire sizes.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.