Electrical machine

An electrical machine comprising:

• a two-part rotor having a rotational axis and formed of:
• a first rotor part which includes a conical section and which is mounted to a shaft of the machine;
• a second rotor part positioned radially outside the first rotor part and which has a bore including a complementary conical section, the second rotor part configured to displace axially between a first state, in which the second rotor part is engaged with the first rotor part to form the rotor of the electrical machine, and a second state, in which the second rotor part is axially disengaged from the first rotor part, the second rotor part including an annular array of permanent magnets on an outer periphery;
• a stator including electrical coils and being positioned radially outside the two-part rotor;
• and
• a clutch having an engaged state and a disengaged state;
• wherein when the clutch is in one of the engaged and disengaged states the second rotor part is in the first state, wherein a switch of the clutch to the other of the engaged and disengaged states axially displaces the second rotor part to the second state, and wherein the clutch comprises an electromagnetic actuator.