What are Torque motors?

A torque motor is a toroid shaped motor which can directly drive the application without additional mechanics, like worm wheels, belts, or pulleys. Because of their shape, torque motors are able to generate a lot of torque, but relatively little RPM compared to conventional servomotors. The latter can reach a much higher RPM, but generate less torque. To reach the desired speed to torque ratio, a coneventional servo motor is therefore often fitted with a gearbox. This gearing reduces the efficiency and accuracy, however.   

There are two types of direct drive torque motors: the outrunner and the inrunner torque motors. In case of a inrunner motor, the rotor is located on the inside of the stator.  In case of the outrunner motor, the rotor is located on the outside of the stator. Outrunner motors produce more torque for the same build volume compared to inrunner motors. Magnetic Innovations is specialised in the outrunner typology. But both type of torque motors, each with their own advantages, still function in a similar way.

In the video below, you can see a visual representation of how a outrunner torque motor works. On the inside is the stator, this is the static part of the torque motor, which contains the lam stack and copper wire. The lam stack contains “lam stack teeth” or “stator teeth”. On each of these teeth copper windings are wound. When three phase AC current is supplied to the copper windings, the stator turns into an array of electromagnets. As a result, an alternating rotating magnetic field is created around the stator, as shown in the video to the right. The orange and blue areas depict the south and north part, respectively. On the outside is the rotor with rare earth permanent magnets. These are consequently attracted and repelled by the alternating elec tromagentic field in the stator teeth, which drives the torque motor as shown below.

The copper windings on the stator can be configured in different ways to create different performance parameters that can be important for various applications in for instance semicon, robotics, food, and packaging industries.

Click here for our other videos on how a torque motor works.