End ring and rotor bar for line start permanent magnet motor

A method comprising:

• accessing a line-start synchronous motor, wherein the motor comprises:
• a stator;
• a rotor core disposed within the stator, the rotor core comprising:
• a plurality of permanent magnets defining a number of poles (P) of the motor;
• a plurality of rotor bars spaced about the rotor core, the rotor bars defining a rotor bar area (BA), the rotor bars being formed of a conductive material having an associated conductivity (σRB);
• and
• end members disposed on axial opposite ends of the rotor core, the end members being in electrical contact with the rotor bars, each end member having a geometric cross sectional area (“ERA”), wherein the end members have a diameter that generally corresponds to an outer diameter of the rotor core, and wherein the ERA is greater than 0.5 times the rotor bar area per the number of poles (BA/P) times a ratio of the rotor bar material conductivity to the end member material conductivity (σRB/σEM);
• operatively coupling a first load to the motor;
• and
• driving the first load from start to at least near synchronous speed during steady state operation of the motor with the first load coupled thereto;
• wherein the first load has an inertia, the first load inertia being greater than an inertia of a second load, the second load inertia being a maximum inertia that a second motor is capable of driving from start to near synchronous speed during steady state operation of the second motor with the second load coupled thereto when the second motor has a rotor with end members with a geometric cross sectional area less than about 0.5 times the rotor bar area per the number of poles (BA/P) times a ratio of the rotor bar material conductivity to the end member material conductivity (σRB/σEM) and the second motor is subjected to an equivalent range of starting current as the motor.