A rotary generator formed of a series of stator annuli (18, 32) and a coaxial series of armature annuli (16, 31) mounted for relative rotational movement around their common axis, wherein the series of stator and armature annuli (16, 18, 31, 32) are affixed circumferentially onto and along the lengths of respective exterior and interior circumferential surfaces of two coaxial hollow elongated cylinders (12, 13), wherein the outer cylinder is directly driven by the available source of mechanical rotary energy, the series of stator annuli (18, 32) interleaving the series of armature annuli (16, 31) and the series of armature annuli (16, 31) interleaving the series of stator annuli (18, 32), and either of the armature/stator annuli (16, 18, 31, 32) each having an associated sequence of coils (19, 34-36, 45, 50, 55, 56) around the common axis, and the other of the armature/stator annuli (16, 18, 31, 32) having a corresponding sequence of permanent magnets (17, 33, 37, 38) of alternating polarity spaced around the common axis, the arrangement being such that lines of magnetic flux passing across an air gap between the magnets (17, 33, 37, 38) in a first of the annuli and the magnets (17, 33, 37, 38) on the next of the annuli cut turns of the coils (19, 34-36, 45, 50, 55, 56) of the corresponding interleaved coil carrying annulus, and thus induce in the coils (19, 34-36, 45, 50, 55, 56) electromagnetic forces as the armature is caused to rotate relative to the stator, wherein the sequence of permanent magnets are spaced around the common axis at the same pitch as that of the coils, the stator coils (19, 34-36, 45, 50, 55, 56) abut one another or substantially abut one another around the circumferential length of the annulus in which they are embedded, the separation of the coils in any event not exceeding by more than 10% that of their natural maximum diameters, and whole annuli or groups (68, 69, 70) of annuli are rotationally displaced relative to one another to achieve the desired variations in phase angle between their respective outputs. wherein the series of stator and armature annuli (16, 18, 31, 32) are affixed circumferentially onto and along the lengths of respective exterior and interior circumferential surfaces of two coaxial hollow elongated cylinders (12, 13), wherein the outer cylinder is directly driven by the available source of mechanical rotary energy, the series of stator annuli (18, 32) interleaving the series of armature annuli (16, 31) and the series of armature annuli (16, 31) interleaving the series of stator annuli (18, 32), and either of the armature/stator annuli (16, 18, 31, 32) each having an associated sequence of coils (19, 34-36, 45, 50, 55, 56) around the common axis, and the other of the armature/stator annuli (16, 18, 31, 32) having a corresponding sequence of permanent magnets (17, 33, 37, 38) of alternating polarity spaced around the common axis, the arrangement being such that lines of magnetic flux passing across an air gap between the magnets (17, 33, 37, 38) in a first of the annuli and the magnets (17, 33, 37, 38) on the next of the annuli cut turns of the coils (19, 34-36, 45, 50, 55, 56) of the corresponding interleaved coil carrying annulus, and thus induce in the coils (19, 34-36, 45, 50, 55, 56) electromagnetic forces as the armature is caused to rotate relative to the stator, wherein the sequence of permanent magnets are spaced around the common axis at the same pitch as that of the coils, the stator coils (19, 34-36, 45, 50, 55, 56) abut one another or substantially abut one another around the circumferential length of the annulus in which they are embedded, the separation of the coils in any event not exceeding by more than 10% that of their natural maximum diameters, and whole annuli or groups (68, 69, 70) of annuli are rotationally displaced relative to one another to achieve the desired variations in phase angle between their respective outputs.