Apparatus and method for determining a temperature of a rotor

A computer-implemented method for determining a temperature of a rotor (3) of an electric machine (2), comprising:

• providing (S1) input variables which are dependent on the operation of the electric machine (2);
• calculating (S2) a first contribution to the heat transfer on the rotor (3) using at least one of the input variables and by means of a physical model, wherein
• the at least one input variable includes a current temperature of the stator (4) and/or a current temperature of the coolant (5), and wherein the computing device (12) is configured to calculate the first contribution to the heat transfer on the rotor (3) using a temperature difference between the current temperature of the stator (4) and the most recently calculated temperature of the rotor (3) and/or using a temperature difference between the current temperature of the coolant (5) and the most recently calculated temperature of the rotor (3), wherein
• the first contribution to the heat transfer on the rotor (3) includes a heat flow from a stator (4) of the electric machine (2) to the rotor (3) and/or a heat flow from a coolant (5) of the electric machine (2) to the rotor (3);
• calculating (S3) a second contribution to the heat transfer on the rotor (3) using at least one of the input variables and by means of an artificial intelligence model (101), wherein
• the artificial intelligence model is trained with test bench measurements to retrospectively group the test bench measurements into distinct labels, wherein
• the test bench measurements are telemetry measurements of the temperature of the rotor (3) under different load and ambient conditions, wherein
• the labels are determined based on a difference between the current temperature of the rotor (3) and the previous temperature of the rotor (3);
• calculating (S4) the temperature of the rotor (3) using the first contribution and the second contribution to the heat transfer on the rotor (3);
• and
• derating the electric machine, based on the calculated temperature of the rotor, to reduce demagnetization of rotor magnets.

A non-transitory, computer-readable storage medium comprising executable instructions that when executed by a computer cause the computer to determine a temperature of a rotor (3) of an electric machine (2), by:

• obtaining (S1) input variables which are dependent on the operation of the electric machine (2);
• calculating (S2) a first contribution to the heat transfer on the rotor (3) using at least one of the input variables and by means of a physical model, wherein
• the at least one input variable includes a current temperature of the stator (4) and/or a current temperature of the coolant (5), and wherein the computing device (12) is configured to calculate the first contribution to the heat transfer on the rotor (3) using a temperature difference between the current temperature of the stator (4) and the most recently calculated temperature of the rotor (3) and/or using a temperature difference between the current temperature of the coolant (5) and the most recently calculated temperature of the rotor (3), wherein
• the first contribution to the heat transfer on the rotor (3) includes a heat flow from a stator (4) of the electric machine (2) to the rotor (3) and/or a heat flow from a coolant (5) of the electric machine (2) to the rotor (3);
• calculating (S3) a second contribution to the heat transfer on the rotor (3) using at least one of the input variables and by means of an artificial intelligence model (101), wherein
• the artificial intelligence model is trained with test bench measurements to retrospectively group the test bench measurements into distinct labels, wherein
• the test bench measurements are telemetry measurements of the temperature of the rotor (3) under different load and ambient conditions, wherein the labels are determined based on a difference between the current temperature of the rotor (3) and the previous temperature of the rotor (3);
• calculating (S4) the temperature of the rotor (3) using the first contribution and the second contribution to the heat transfer on the rotor (3);
• and
• derating the electric machine, based on the calculated temperature of the rotor, to reduce demagnetization of rotor magnets.