A permanent magnet electrical machine has a rotor supporting a circumferential row of permanent magnets. The electrical machine further has a stator coaxial with the rotor and having a circumferential row of stator teeth carrying respective coils. The teeth provide paths for magnetic flux produced by the magnets, thereby electromagnetically linking the magnets and the coils when the rotor rotates relative to the stator. The teeth have respective core portions on which the coils are mounted, and respective tip portions located between the core portions and the rotor, neighbouring tip portions being circumferentially spaced from each other by respective gaps. Each pair of neighbouring tip portions has a bridge member and a thermal switching mechanism carried by a first tip portion of the pair.