Understanding Torque and Speed in Electric Motors
When selecting an electric motor for an application, regardless of project size or industry, two of the most critical performance factors to consider are torque and speed. These elements determine how well the motor can perform specific tasks, such as lifting heavy loads, running at high speeds, or providing precise control in an industrial setting.
The Importance of Torque
In essence torque is a measure of the rotational force produced by an electric motor and therefore the force available to rotate an object, such as a conveyor belt, fan, or machinery components.
The higher the torque, the greater the ability to rotate heavy objects, overcome tough resistance or to transport objects vertically. Applications which rely on high torque can include hoists and cranes, as well as industrial mixing machines.
The Need for Speed
The speed refers to how fast the motor’s output shaft rotates. High-speed motors rotate faster and are ideal for applications where rapid movement or high rotational velocity is required.
High speed motors can often be found in HVAC (heating, ventilation and air conditioning) systems or conveyor systems within the manufacturing industry which requires fast-paced activity.
The Relationship Between Speed and Torque
There is an inverse relationship between torque and speed in electric motors. As the speed increases the torque decreases, and vice versa. So, in the simplest terms, when the motor has a low speed it has a high torque, and when it has a fast speed it produces lower torque.
A motor with a low speed but high torque is suited for lifting or rotating heavy goods or where precise and powerful force is required. Such applications will include; conveyor belt systems which move heavy products across production lines; winches, hoists and cranes which need to move heavy objects carefully. Drilling equipment is also used to work through tough materials which require force and precision.
Alternatively, a high-speed motor with low torque is ideal for applications which don’t require heavy lifting such as: medical laboratory equipment like centrifuges and pumps which rely on fast rotation, but minimal power; food processing equipment, such as blenders and slicers; HVAC; and irrigation systems where moving liquid doesn’t encounter much resistance.
The Importance of Control
Getting the right combination of speed and torque is vital for the success of your project, as different applications require different combinations. There are two main ways of adjusting these combination ratios: changing gear ratios, and motor winding adjustments.
Geared Motors
Combining your electric motor with a gearbox can make adjusting torque and speed easier.
- High-Torque, Low-Speed Applications – Geared motors with high gear ratios are often used to increase torque whilst reducing speed.
- High-Speed, Low-Torque Applications – Motors with lower gear ratios are used to increase speed whilst reducing torque.