What is the relationship between speed and torque in electric motors?

In electric motors, there is a fundamental relationship between speed and torque, which is reflected in the operating characteristics of the motor. As speed increases, it typically results in a decrease in torque. This relationship is a result of the principles of electromagnetic induction and the design of electric motors.

When an electric motor operates at higher speeds, the motor generates a back electromotive force (back EMF) that opposes the supply voltage. This back EMF increases with speed. Consequently, for a given power supply, more of the voltage is used to overcome this back EMF, which leads to less voltage being available to produce current through the motor's windings. Since torque in a motor is proportional to the current flowing through it, a reduction in current directly translates to a decrease in torque at higher speeds.

This principle is commonly exemplified in applications such as electric vehicles, where high-speed operation can lead to a significant reduction in available torque, thereby impacting acceleration. Understanding this relationship helps in the selection and application of electric motors for various tasks where both speed and torque are critical parameters.