Electrical machine having stator sleeve

A method of operating an electrical machine,

• the electrical machine comprising:
• a rotor at least partially disposed within a rotor chamber, a stator core coaxially arranged with the rotor chamber and defining a plurality of stator core slots in which a respective stator winding is provided, and an annular stator sleeve positioned between the stator core and the rotor chamber, the stator sleeve comprising a magnetic material having a relative permeability of at least 10 and an intrinsic coercivity no greater than 1 kAm−1,
• the method comprising:
• operating the electrical machine in a baseline condition;
• and
• operating the electrical machine in a fault condition in which the stator windings are electrically connected to each other to form a short-circuit,
• wherein the stator sleeve provides additional effective inductance to the stator windings such that a fault current induced within the stator windings is inhibited.

An electrical machine comprising:

• a rotor at least partially disposed within a rotor chamber,
• a stator core coaxially arranged with the rotor chamber, and
• a stator sleeve,
• wherein the stator sleeve is annular and is positioned between the stator core and the rotor chamber;
• wherein the stator sleeve comprises a magnetic material having a relative permeability of at least 10 and an intrinsic coercivity no greater than 1 kAm−1;
• wherein the stator sleeve has a composite structure comprising a matrix and a filler distributed in the matrix, wherein the filler comprises the magnetic material;
• and
• wherein the filler comprises elongate wires extending through the matrix, wherein the matrix separates the elongate wires to electrically insulate the elongate wires.