Rotating electromechanical converter (2, 80) comprising, arranged around a common axis: - a stator (10, 88) comprising magnetic circuits and polyphase energising windings (12, 90), - an inner-rotor (14, 92) at a distance from said stator (10, 88) and coupled to a first externally accessible shaft (22, 96), comprising magnetic circuits and polyphase energising windings (16, 116), and - an inter-rotor (18, 104) between the inner-rotor (14, 92) and the stator (10, 88), coupled to a second, externally accessible, shaft (28, 107), comprising magnetic circuits and permanent magnetic members (20, 56, 106) for co-operation with the magnetic circuit of at least the stator (10, 88) such that a magnetic flux generated by these permanent magnetic members (20, 56, 106) traverses both these magnetic rotor circuits and stator circuits, wherein the stator has a cylindrical configuration and surrounds via a first air gap the sleeve shaped inter-rotor which has a first outer surface directed towards the stator and a second outer surface directed towards the inner-rotor, a second air gap being present between this second outer surface and the cylindrical inner-rotor, characterized by - means for modifying the state of magnetisation of at least a part of the respective inter-rotor areas (62, 135, 162) which each lie between two successive permanent magnetic members (20, 56, 106), wherein said means comprise at least one externally accessible control winding (19, 61, 134) for carrying a DC current, the arrangement of the permanent magnetic members (20, 56, 106) and the control winding (19, 61, 134) being such that the respective fluxes, generated by the permanent magnetic members (20, 56, 106) on the one hand and by the current in the at least one control winding (19, 61, 134) on the other hand, share in the inter-rotor (18, 104) at least one common magnetic circuit occupying at least a part of the respective interrotor areas between successive permanent magnetic members (20, 56, 106), and extending in the circumferential direction of the inter-rotor, wherein the permanent magnetic members (20, 56) have each a first pole directed to said inner-rotor and a second, opposite, pole directed to the stator, said poles having a first magnetic polarity and a second magnetic polarity respectively, said polarities alternating, in the circumferential direction, between adjacent poles, wherein first magnetic circuits being present starting from each first pole and extending across the adjacent second air gap through the magnetic circuits of the inner-rotor back to each adjacent pole of opposite polarity, wherein second magnetic circuits being present starting from each second pole and extending across the first air gap and through the magnetic circuits of the stator to each adjacent pole of opposite polarity, wherein the inter-rotor is provided with the control winding (19, 61) lying adjacent said common magnetic circuits and arranged circumferentially between poles of opposite polarity formed by said permanent magnetic members (20, 56), being able to carry the controllable electrical DC current such that the magnetic fluxes generated by the current flowing in said control winding (19, 61) are superimposed on the magnetic fluxes provided by the permanent magnetic members (20, 56) and passing through these common magnetic circuits, and thereby control the magnetic flux density in at least one of the magnetic circuits in the stator or inner-rotor. - a stator (10, 88) comprising magnetic circuits and polyphase energising windings (12, 90), - an inner-rotor (14, 92) at a distance from said stator (10, 88) and coupled to a first externally accessible shaft (22, 96), comprising magnetic circuits and polyphase energising windings (16, 116), and - an inter-rotor (18, 104) between the inner-rotor (14, 92) and the stator (10, 88), coupled to a second, externally accessible, shaft (28, 107), comprising magnetic circuits and permanent magnetic members (20, 56, 106) for co-operation with the magnetic circuit of at least the stator (10, 88) such that a magnetic flux generated by these permanent magnetic members (20, 56, 106) traverses both these magnetic rotor circuits and stator circuits, - means for modifying the state of magnetisation of at least a part of the respective inter-rotor areas (62, 135, 162) which each lie between two successive permanent magnetic members (20, 56, 106), wherein said means comprise at least one externally accessible control winding (19, 61, 134) for carrying a DC current, the arrangement of the permanent magnetic members (20, 56, 106) and the control winding (19, 61, 134) being such that the respective fluxes, generated by the permanent magnetic members (20, 56, 106) on the one hand and by the current in the at least one control winding (19, 61, 134) on the other hand, share in the inter-rotor (18, 104) at least one common magnetic circuit occupying at least a part of the respective interrotor areas between successive permanent magnetic members (20, 56, 106), and extending in the circumferential direction of the inter-rotor,