Base Speed, Constant-Torque, and Constant-Power Regions
Base speed is the approximate transition between the current-limited and voltage-limited parts of an electric motor's operating range. It is a control boundary, not necessarily one fixed vehicle speed.
Constant-torque region
Below base speed, the inverter can often supply the current needed for nearly constant maximum torque. Because motor power equals torque multiplied by rotational speed, power rises as the motor turns faster.
Constant-power region
As speed increases, back electromotive force approaches the available inverter voltage. The controller then weakens the effective field so the motor can rotate faster. Maximum torque falls, while power can remain approximately constant over part of the range.
Practical limits
The regions are not perfectly flat. Battery voltage, inverter current, winding temperature, rotor limits, cooling, and control strategy reshape the envelope. At still higher speeds, power may fall as voltage, current, efficiency, or mechanical constraints become dominant. Motor control and efficiency maps
Maps must state their boundary and conditions; a short-duration peak envelope is not the same as a continuous one. torque-speed and efficiency maps