Air-Gap Wound Alternators for Large-Scale Power Generation

  • Edward Spooner

Student thesis: Doctoral ThesisDoctor of Philosophy


The airgap-wound or slotless alternator is similar to the
conventional type of alternator used for central power
generation, but the windings of both the fixed and rotating
components are situated in the gap normally separating the two,
rather than in slots milled into the steel surfaces. It is
shown that this seemingly trivial modification can result in
large reductions in the length, weight, losses and cost of
generators if properly designed. In addition output capacities
about four times that of the largest possible conventional
machine could be obtained.

In chapters 1, 2 and 3 the constraints applying to the new
layout are explained, methods of obtaining optimum dimensions
and specific loadings sre set out and several designs are
compiled to demonstrate the possibilities of the slotless
design. In chapter 5, comparison is made between slotless and
conventional machines and it is seen that the slotless type offers
several advantages. In particular, a 660 MW slotless machine
would be about 4 m shorter, 150 tonne lighter, would have about
2 MW lower losses and would give a total cost saving of about

The design of certain critical components is examined in
chapter 4 and some specific problem areas are considered in the
Date of Award1972
Original languageEnglish


  • Air-gap wound altemators
  • power generation

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