Motors, Generators & Electrification Equipment worked example

Copper Fill Factor at 30% target slot copper fill factor: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop target slot copper fill factor to 30%, then walk the calculation through step by step. Calculate stator slot copper fill factor so winding and design engineers can see how much of the slot the conductors occupy and compare it to the design target.

The inputs for this scenario

  • Net copper conductor area in the slot: 100 mm² (held at the documented default)
  • Total stator slot cross-section area: 250 mm² (held at the documented default)
  • Target slot copper fill factor: 30 % (the input this scenario stresses; the baseline uses 42)

Working through the calculation

  • The calculation starts from the formula this tool documents: Copper fill factor = copper conductor area in slot ÷ total slot area × 100.
  • Copper fill factor works out to 40 % at these inputs, and this is the headline figure for the scenario.
  • Fill factor gap to target works out to -10 points at these inputs.
  • Copper conductor area in slot works out to 100 count at these inputs.
  • Total slot area works out to 250 count at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where target slot copper fill factor sits at 42% and the headline result is 40 %, this scenario lands almost exactly on the baseline at 40 %.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to target slot copper fill factor, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It uses net conductor (bare copper) area; if you instead enter the insulated wire area you will overstate fill, and the formula says nothing about whether the slot is physically windable at that fill.

Results at a glance

  • Copper fill factor: 40 % (headline result)
  • Fill factor gap to target: -10 points
  • Copper conductor area in slot: 100 count
  • Total slot area: 250 count

Run it with your numbers

  • To rerun this with your own numbers, open the live Copper Fill Factor calculator, set target slot copper fill factor to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.