A motor’s power output is a key consideration when sourcing an electric motor for any type of application. Power output can be a complex thing to consider, however, as it is determined by many factors, most notably the motor’s speed and torque. To understand a motor’s fit for your application, it is important to first know the differences between speed and torque and the impact each has on the power output of a motor.
The Basics of Speed and Torque
In order to fully understand the concepts of speed and torque, we must begin by defining each term:
- Speed: The speed of a motor, at its most basic form, is the rate at which the motor spins. The speed of an electric motor is measured in rotations per minute, or RPM.
- Torque: The torque output of a motor, at its most basic form, is the amount of rotating force the motor develops. The torque of an electric motor is measured in pounds per force inch or lb-in.
The two factors largely determine the power output of an electric motor. Power can be determined by the following equation: Power (P) = Speed (w) x Torque (T).
Considering Speed and Torque When Sourcing Electric Motors
Speed and torque are the key variables in determining the power required from a motor. This information is critical in choosing the right motor for an application. Selecting a motor that provides the proper amount of speed required for an application but not the minimal torque will result in operational issues. Conversely, a motor that meets the necessary torque rating, but lacks the required speed, may be a poor fit for the application.
Fortunately, once you choose an appropriately sized motor, you have flexibility to trade off speed and torque to meet the requirements for an application. You can alter each factor by adjusting the wire size and number of turns of wire in the motor. More turns of smaller wire will result in more torque, at the expense of speed. Conversely, you can achieve more speed by winding fewer turns of a larger wire size, but you will then see a reduction in torque.