Innovative Low-Cost Sub-Fractional HP BLDC Claw-Pole Machine Design for Fan Applications

Stefan Leitner, Hannes Grübler, Annette Muetze

Research output: Contribution to journalArticlepeer-review


As for mass-produced sub-fractional horsepower drives, non-optimal motor behavior (e.g., high cogging torque, output torque ripple, and noise) is often accepted when cost can be reduced, provided reliability is not compromised. This paper proposes an innovative claw-pole motor design for a low-cost single-phase brushless direct current fan drive, improving motor behavior with no increase to the manufacturing cost: 1) reducing cogging torque by proposing unconventional claw-pole skewing and 2) ensuring self-starting capability by implementing air-gap asymmetry. Both measures help reduce the total output torque ripple. The goal is to reduce fan drive noise, especially at low-speed operation, where cogging torque is often the dominating noise source. The design of stator claw skewing and air-gap asymmetry is presented; their effects on motor quantities are studied via simulations and experiments. With the exception of a small reduction of about 1.8% in the back electromotive force fundamental, skewing the stator claws by 30^{\circ } can reduce the cogging torque by 23% in the simulations and by 28% in the experiments.

Original languageEnglish
Article number8606100
Pages (from-to)2558-2568
Number of pages11
JournalIEEE Transactions on Industry Applications
Issue number3
Publication statusPublished - 9 Jan 2019


  • Air-gap asymmetry
  • bifilar winding
  • brushless direct current (BLDC)
  • claw-pole
  • cogging torque
  • fan drives, low-cost
  • skewing
  • sub-fractional horsepower (hp)
  • torque measurement
  • torque ripple

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering

Fields of Expertise

  • Mobility & Production


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