Measured radial resistor grid fan speed and control

A method of operating an electric drive machine, the method comprising:

• determining, by one or more processors, an active cooling capacity of a fan coupled to a resistor grid, wherein the active cooling capacity of the fan is determined when the fan is receiving power and is in an active cooling mode;
• determining, by the one or more processors, a passive cooling capacity of the fan coupled to the resistor grid, wherein the passive cooling capacity of the fan is determined after the fan is switched from the active cooling mode to an off mode;
• determining, by the one or more processors, a target cooling load to meet a power duty of the resistor grid;
• determining, by the one or more processors, a target cooling capacity using a combination of the active cooling capacity and the passive cooling capacity;
• and
• controlling, by the one or more processors, power to the fan to provide the target cooling load to the resistor grid, using the combination of the active cooling capacity of the fan and the passive cooling capacity of the fan, the combination providing the target cooling capacity corresponding to the target cooling load.

An electric drive machine comprising:

• a resistor grid electrically coupled to a motor of the electric drive machine;
• a fan including a plurality of fan blades rotatably coupled to a fan motor;
• a speed sensor configured to measure a rotational speed of the fan;
• and
• a control circuit comprising one or more processors and a memory structured to store instructions that, when executed by the one or more processors, cause the control circuit to:
• determine an active cooling capacity of the fan according to a measured rotational speed of the fan while the fan motor is in an active cooling mode;
• determine a passive cooling capacity of the fan according to a measured rotational speed of the fan after the fan motor is switched from the active cooling mode to an off mode;
• determine a target cooling load to meet a power duty of the resistor grid;
• determine a target cooling capacity using a combination of the active cooling capacity and passive cooling capacity;
• and
• control power to the fan motor to provide the target cooling load, using the combination of the active cooling capacity of the fan and the passive cooling capacity of the fan, the combination providing the target cooling capacity corresponding to the target cooling load.