Abstract: Insulation of multiturn high voltage stator windings is effected by applying interturn insulation in the form of glass-backed mica paper pre-treated with resin taken to a B-stage cure, at least to straight slot-engaging parts of the windings. The interturn insulation is mechanically consolidated and thermally cured and main insulation is then applied to the slot-engaging parts and end parts of the windings and consists of glass backed mica paper pre-treated with resin without a curing agent. The slot engaging parts are next mounted on the stator and the end parts of the windings are connected to them to form electrically completed windings which are then impregnated with a resin compound by a vacuum and pressure process followed by a thermal cure.