Helical Windings in Electrical Machines

Dr. Antony Anderson C.Eng FIEE

Helical windings are not new and found limited Favour for dynamos in Germany in the late 1880s. [Fritsche] Today They Are Widely Used For small dc machinery of the ironless kind, where 'THEY offer the advantage of low inertia and smooth torque at low speeds. They Have Been Used For aussi linear motors [Eastham & Laithwaite] and transverse flux tubular motors [Eastham & Alwash]. The wide use in ac machine WAS Proposed first by Ross Anderson and Macnab of the International Research and Development Company Ltd., Who Suggested it as A Suitable frame for superconducting ac generators [UK patent 1975] and This Was Followed up by a detailed analysis of Theoretical [Anderson, Bumby and Hassall] published in 1980. A helical armature winding 4 MVA WAS Used by Watnabe et al. as the armature winding for use in a slotless Either gold superconducting generator. Conley et al. Used in a helical winding 10 MVA superconducting year experimental generator at MIT in the late 1970s.

                                                Explanation of the helical winding

Unlike the Conventional winding, the winding helical Has No separate division Into active regions and end, Because EACH conductor follows a helical path of constant pitch and diameter from one end of the machine to The Other. In the Conventional winding contents, each year follows the axial conductor path in the active area and only a circumferential component to HAS icts path in the end regions.

To Understand how a helical winding works, Consider the winding length of a diamond lap winding shown in the adjacent figure (a) To Be Progressively Reduced as (b), by Eliminating the central So-Called "active" region and allowing The Two diamond end windings to coalesce and form a semi-helical winding (c). The true helical winding (d) evolves from the wave winding wound diamond (d).

                          Relationship to Conventional lap of helical windings and diamond

One phase of a two pole helical winding is Shown Above. Each phase Consists of Two parallel-connected helical loops contents, each of Which is interest rated a phase group. Each phase group included one right-hand (inner) helical band phase connected in series with a Returning left-hand (outer) phase helical band, a band right hand phase Being Defined as That Which traces a right hand screw.
 

                                                   Helical armature for a small DC motor