Structural mass in direct-drive permanent magnet electrical generators

Alasdair McDonald, Markus Mueller, Henk Polinder

Research output: Contribution to journalArticlepeer-review

84 Citations (Scopus)


Direct-drive permanent magnet (PM) synchronous machines for wind turbines are large, heavy and thus expensive to build, transport and install. The structure that is required to maintain the airgap clearance is often heavier than the electromagnetically active material. It is shown that the structural material can be estimated early on in the design process for axial-flux and radial-flux machines. By moving to a design without iron in the stator, the forces that the machine structure must deal with can be significantly reduced. The mass of iron-cored and air-cored axial-flux PM synchronous machines for a range of multi-MW wind turbines is compared. Scaling laws for PM generators in direct-drive wind turbines are also developed.
Original languageEnglish
Pages (from-to)3-15
Number of pages13
JournalIET Renewable Power Generation
Issue number1
Publication statusPublished - Mar 2008


  • air gaps
  • electric drives
  • permanent magnet generators
  • synchronous generators
  • wind turbines


Dive into the research topics of 'Structural mass in direct-drive permanent magnet electrical generators'. Together they form a unique fingerprint.

Cite this