Electric Motors
Motor Cable Power Loss Calculator
Motor Cable Power Loss provides a checkable estimate of cable loss. It is intended for scenario comparison, not as automatic approval of a component or installation.
Calculate Cable loss
Keep every entry on the units shown below.
Values this page needs
Separate shaft output power from electrical input power. Nameplate and meter values are not interchangeable unless they describe the same condition.
Use the displayed unit for every field and document conversions separately. If you also need DC cable loss, continue with Solar DC Cable Loss Calculator.
- Motor current
- Default example: 30 A. Enter motor current in A.
- Cable resistance
- Default example: 0.12 Ω. Enter cable resistance in Ω.
Understanding the equation
Here, Cable loss is obtained from three-phase loss = 3I²R. Only Motor current and Cable resistance enter the numerical result.
Using the loaded examples gives 324.00 W. Your saved case should identify where each entry came from.
Calculate cable loss from motor current and cable resistance. The broader analysis may also use Three-Phase Motor Current Calculator.
Changing Motor current
Change Motor current from 30 A to 36 A with every other entry unchanged. The result changes from 324.00 W to 466.56 W.
Do not average the two cases if either could define an operating limit.
What the number means
The calculated Cable loss is meaningful only with its input conditions attached. Compare it with starting demand, running current, torque, efficiency, slip, and thermal loading.
Save the raw entries before testing another scenario.
Where this estimate can fail
Resistance is per phase conductor.
Outside the entered variables, consider voltage imbalance, drive waveform, transient torque, and bearing load. Document which effects were checked elsewhere in the analysis.
Separate shaft output power from electrical input power.
A final reasonableness check
Begin by confirming cable resistance at the operating point represented by the other entries. Record whether it came from a meter, nameplate, data sheet, or design assumption.
Use cable loss alongside starting demand, running current, torque, efficiency, slip, and thermal loading. Preserve the unrounded number until all dependent calculations and comparisons are complete.
Document any effect handled outside this page, especially starting method, service factor, enclosure, and thermal duty. That note prevents a later reader from assuming the simple equation covered it.
Questions about inputs and assumptions
Should intermediate values be rounded?
Retain the raw result for comparison and create a separately rounded reporting value if needed.
Should a blank measurement be entered as zero?
Use zero only when it describes the physical condition. It is not a substitute for missing data.