An insulated winding wire may include a conductor and insulation formed around the conductor. The insulation may include a base insulation layer formed around the conductor and having a first dielectric constant (ε1). The insulation may further include an extruded thermoplastic layer formed around the base insulation layer and having a second dielectric constant (ε2). The extruded thermoplastic layer may include (i) at least one polymer comprising a ketone group and (ii) at least one fluoropolymer. A ratio of the dielectric constant (ε2) of the extruded thermoplastic layer to the dielectric constant (ε1) of the base layer at 250° C. may be less than or equal to approximately 1.0.