An electrical generator (1; 600) comprising: a stator (200; 700) comprising one or more electrical windings (238; 712); and a rotor (100; 650) comprising one or more permanent magnets, the rotor being arranged to be rotatable with respect to the stator about an axis of rotation, in which the rotor is located further from the axis of rotation than the stator; a housing, the rotor and the stator being located within the housing; and an axle (300; 750) on which the stator and the rotor are mounted coaxially, wherein one or more wiring holes are formed in the axle, and electrical wiring for the one or more electrical windings passes through the one or more holes in the axle; wherein the electrical windings comprise heat transfer channels through which a fluid may flow so as to transfer heat between the fluid and the electrical windings; wherein the electrical generator further comprises one or more isolating connectors coupled to the heat transfer channels for electrically isolating the electrical windings from the fluid, wherein the one or more isolating connectors comprise: an isolating disc; a pair of coupling discs located either side of the isolating disc; and a connector frame for holding the isolating disc the pair of coupling discs together, the connector frame comprising: a pair of frame discs located either side of the coupling discs and linked by bolts so that the connector frame can compress the coupling discs to the isolating disc in a direction perpendicular to a plane of the discs, and a pair of frame isolation discs (299a, 299b) located between the coupling discs and the frame discs so as to electrically isolate the coupling discs from the connector frame. a stator (200; 700) comprising one or more electrical windings (238; 712); and a rotor (100; 650) comprising one or more permanent magnets, the rotor being arranged to be rotatable with respect to the stator about an axis of rotation, in which the rotor is located further from the axis of rotation than the stator; a housing, the rotor and the stator being located within the housing; and an axle (300; 750) on which the stator and the rotor are mounted coaxially, wherein one or more wiring holes are formed in the axle, and electrical wiring for the one or more electrical windings passes through the one or more holes in the axle; wherein the electrical windings comprise heat transfer channels through which a fluid may flow so as to transfer heat between the fluid and the electrical windings; wherein the electrical generator further comprises one or more isolating connectors coupled to the heat transfer channels for electrically isolating the electrical windings from the fluid, wherein the one or more isolating connectors comprise: an isolating disc; a pair of coupling discs located either side of the isolating disc; and a connector frame for holding the isolating disc the pair of coupling discs together, the connector frame comprising: a pair of frame discs located either side of the coupling discs and linked by bolts so that the connector frame can compress the coupling discs to the isolating disc in a direction perpendicular to a plane of the discs, and a pair of frame isolation discs (299a, 299b) located between the coupling discs and the frame discs so as to electrically isolate the coupling discs from the connector frame. an isolating disc; a pair of coupling discs located either side of the isolating disc; and a connector frame for holding the isolating disc the pair of coupling discs together, the connector frame comprising: a pair of frame discs located either side of the coupling discs and linked by bolts so that the connector frame can compress the coupling discs to the isolating disc in a direction perpendicular to a plane of the discs, and a pair of frame isolation discs (299a, 299b) located between the coupling discs and the frame discs so as to electrically isolate the coupling discs from the connector frame. a pair of frame discs located either side of the coupling discs and linked by bolts so that the connector frame can compress the coupling discs to the isolating disc in a direction perpendicular to a plane of the discs, and a pair of frame isolation discs (299a, 299b) located between the coupling discs and the frame discs so as to electrically isolate the coupling discs from the connector frame.