Determination of permanent magnetic flux in an electric machine

A method for determining magnetic flux in an electric machine assembly, the electric machine assembly including an electric machine with a stator having stator windings, a rotor having a rotor temperature and configured to rotate at a rotor speed (ω), and a controller operatively connected to the electric machine, the controller having a processor and tangible, non-transitory memory, the method comprising:

• determining a total permanent magnetic flux (ψT) as a function of the rotor temperature, including determining a high-speed magnetic flux factor (ψH) and a low-speed magnetic flux factor (ψL);
• wherein the total permanent magnetic flux (ψT) is based at least partially on a weighting factor (k), the high-speed magnetic flux factor (ψH) and the low-speed magnetic flux factor (ψL), such that:
• ψT=[k*ψH+(1−k)*ψL] and 0<k<1;
• wherein the weighting factor (k) is one when the rotor speed (ω) is above a predefined high speed threshold;
• and
• wherein the weighting factor (k) is zero when the rotor speed (ω) is below a predefined low speed threshold;
• and
• controlling the electric machine based upon the total permanent magnetic flux factor (ψT) for efficiency.

A method for determining magnetic flux in an electric machine assembly, the electric machine assembly including an electric machine with a stator having stator windings, a rotor having a rotor temperature and configured to rotate at a rotor speed (ω), and a controller operatively connected to the electric machine, the controller having a processor and tangible, non-transitory memory, the method comprising:

• determining a total permanent magnetic flux (ψT) as a function of the rotor temperature, including determining a high-speed magnetic flux factor (ψH) and a low-speed magnetic flux factor (ψL);
• controlling the electric machine based upon the total permanent magnetic flux factor (ψT) for efficiency;
• and
• wherein determining the total permanent magnetic flux (ψT) includes:
• obtaining a look-up factor, via the controller, as a slope of a portion of a graph of a characterized torque error versus the torque command (T*), the portion being below 80% of a maximum of the torque command (T*);
• wherein the characterized torque error is defined as a difference between two independent estimates of torque produced by the electric machine;
• and
• obtaining a first function (F1), via the controller, as a product of the look-up factor and the torque command (T*).