Torque-Speed and Efficiency Maps
Torque–speed and efficiency maps describe different properties of an electric drive across its operating range. Reading them together is more informative than comparing one peak number.
Torque–speed map
A torque–speed map shows the positive and regenerative torque available at each rotational speed. Its outer envelope can change with voltage, temperature, cooling, duration, and mechanical limits. Below base speed, current often limits torque; at higher speed, voltage and back electromotive force become increasingly important.
Efficiency map
An efficiency map places efficiency contours across combinations of speed and torque. The highest-efficiency island is not necessarily where the vehicle spends most of its time. Urban driving, motorway cruising, climbing, towing, and acceleration visit different points.
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Check whether a map covers the motor, motor plus inverter, or complete drive unit. Also check DC voltage, temperatures, motoring versus regeneration, and whether values are measured or simulated. Motor control and efficiency maps A broad useful region can matter more to vehicle consumption than the single best point.
The maps also explain the connection between torque, motor power, and the base speed, constant-torque, and constant-power regions used above base speed.