Magnet shaping and pole concentration for reduction of cogging torque in permanent magnet motors

A rotor for a permanent magnet motor, comprising:

• a rotor yoke;
• and
• a permanent magnet ring adhered to the rotor yoke, the permanent magnet ring including a plurality of circumferentially spaced poles and the permanent magnet ring having a radial edge opposed to the rotor yoke, the radial edge having a first constant radius;
• one of the rotor yoke and the permanent magnet ring including a plurality of depressions along a peripheral edge adjacent the other of the permanent magnet ring and the rotor yoke;
• and
• the plurality of depressions shaped so the motor produces a sinusoidal flux density during operation.

A rotor for a permanent magnet motor, comprising:

• a rotor yoke;
• and
• a permanent magnet ring adhered to the rotor yoke, the permanent magnet ring including a plurality of circumferentially spaced poles and the permanent magnet ring having a radial edge opposed to the rotor yoke, the radial edge having a first constant radius;
• one of the rotor yoke and the permanent magnet ring including a plurality of depressions along a peripheral edge adjacent the other of the permanent magnet ring and the rotor yoke;
• and
• the plurality of depressions shaped so the motor produces a sinusoidal flux density during operation;
• and wherein the peripheral edge has a second constant radius between the plurality of depressions.

A rotor for a permanent magnet motor, comprising:

• a rotor yoke;
• and
• a permanent magnet ring adhered to the rotor yoke, the permanent magnet ring including a plurality of circumferentially spaced poles and the permanent magnet ring having a radial edge opposed to the rotor yoke, the radial edge having a first constant radius;
• one of the rotor yoke and the permanent magnet ring including a plurality of depressions along a peripheral edge adjacent the other of the permanent magnet ring and the rotor yoke;
• and
• the plurality of depressions shaped so the motor produces a sinusoidal flux density during operation;
• and wherein the other of the rotor yoke and the permanent magnet ring has a radial edge having a third constant radius and adjacent the peripheral edge.

A rotor for a permanent magnet motor, comprising:

• a rotor yoke wherein the rotor yoke is non-magnetized;
• and
• a permanent magnet ring mounted on the rotor yoke, the permanent magnet ring including a plurality of circumferentially spaced poles, and wherein a radially-inner peripheral edge of the permanent magnet ring has a constant diameter;
• one of the rotor yoke and the permanent magnet ring being an annular member including depressed portions along a radially-outer peripheral edge;
• and
• the depressed portions shaped so the motor produces a sinusoidal flux density during operation.

A rotor for a permanent magnet motor, comprising:

• a rotor yoke wherein the rotor yoke is non-magnetized;
• and
• a permanent magnet ring adhered to the rotor yoke, the permanent magnet ring including a plurality of circumferentially spaced poles and the permanent magnet ring having a radial edge opposed to the rotor yoke, the radial edge having a first constant radius;
• one of the rotor yoke and the permanent magnet ring being an annular member including depressed portions along a radially-outer peripheral edge;
• and
• the plurality of depressions shaped so the motor produces a sinusoidal flux density during operation.