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Hairpin Stator Inspection

Definition

CT-based quality assurance of e-motor hairpin windings covering position accuracy, insulation layer and contact resistance

Synonyms:
Hairpin CTStator Inspection CTE-Motor CTHairpin Winding Inspection

What is Hairpin Stator Inspection?

Hairpin stator inspection refers to CT-based quality assurance of electric motors using hairpin winding technology. Hairpin windings consist of U-shaped bent copper flat conductors (hairpins) inserted into the stator slots and connected at the end faces. Compared to classical round conductors, they enable higher fill factors and better thermal conductivity. CT allows complete inspection without disassembling the encapsulated stator.

Scientific background

Critical inspection characteristics are the position accuracy of hairpins in the slots (positional tolerances < 100 µm), the thickness and integrity of the enamel insulation, the quality of the laser welds at the contact points and the absence of copper shavings or foreign particles in the slot area. CT provides three-dimensional grey-value datasets from which geometric and topological features can be evaluated automatically.

Relevant key metrics

  • Hairpin position tolerance in slot: typically ± 50–100 µm.
  • Smallest detectable insulation defects: ≥ 20–50 µm thickness underrun.
  • Foreign-particle detection: copper particles from approx. 50 µm detectable.

Standards and thresholds

  • Standards: IEC 60034-1 (rotating electrical machines), IEC 60317 (requirements for enamelled wires), ISO 16750 (environmental conditions for electrical/electronic automotive equipment), VDA 6.3 (process audit).
  • Typical thresholds: Manufacturer- and assembly-specific; foreign particles > 100 µm in the slot are often an exclusion criterion.
  • Validity: Inspection scope is defined per DFMEA and process FMEA of the stator manufacturer; sampling vs. 100 % inspection depending on SOP phase and error rate.

Application in industrial practice

  • Series-accompanying 100 % inspection or statistical sampling in hairpin production.
  • Failure analysis for insulation failure or increased contact resistance.
  • Process optimisation during insertion, bending and welding of hairpins.

Sources and reference date

  • IEC 60034-1:2022.
  • IEC 60317-0-1:2013.
  • ISO 16750-1:2023.
  • VDA 6.3:2023.
  • Reference date: March 2026.

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