VALICALC · ENGINEERING WORKFLOW
Motor cable voltage-drop check
Turn shaft power, voltage, efficiency and power factor into a running-current estimate, then check cable voltage drop and conductor geometry.
Start this workflowWhat do I need to know first?
- Motor nameplate shaft output in kW or HP and supply system
- Line-to-line voltage for three phase; operating efficiency and power factor
- One-way cable length, conductor material, operating temperature and a candidate size
Goal and model boundaries
Estimate the operating current and voltage drop of a proposed motor cable before a separate electrical design review.
- This is a steady running-current estimate; starting current and transient drop are outside the model.
- Neither this workflow nor its wire tables establish ampacity or code compliance. Use nameplate and manufacturer data for the final design.
Estimate running current
Select the motor supply and enter shaft output, efficiency and power factor.
For balanced three phase, I = Pshaft / (η × √3 × VLL × PF).
- Expected output
- Operating current in amperes, with electrical input power.
- Next step
- Carry the current to a cable check, or replace it with measured/nameplate current.
Confirm conductor geometry
Identify a proposed metal area or AWG gauge.
Read bare conductor area; preserve the specified material and insulation separately.
- Expected output
- A candidate area in mm² and its AWG designation.
- Next step
- Enter the candidate area and operating temperature in Voltage Drop.
Check running voltage drop
Choose the correct circuit and use one-way length.
The resistive model scales conductor resistance by length, temperature and circuit factor.
- Expected output
- Voltage drop, percent drop and estimated load voltage.
- Next step
- Compare against your project criterion; review ampacity, starting behavior and protection separately.
Units and context
- Mechanical shaft kW is divided by efficiency before applying the electrical power equation.
- AWG/mm² lookups describe metal geometry; cable outside diameter is a different quantity.
Common mistakes to avoid
- Treating shaft output as electrical input
- Entering the two-way cable length in a one-way field
- Using voltage-drop sizing as an ampacity or protective-device check
Related engineering jobs
Three-phase motor power and current check
Separate shaft output, real input power, apparent power and running current for a balanced three-phase motor; carry a checked current into a cable calculation.
Plan the job →ENGINEERING WORKFLOW · 3 STEPSDC wire selection by voltage drop
Choose a conductor area or maximum one-way cable length for a DC circuit using an explicit voltage-drop budget and wire geometry lookup.
Plan the job →