High torque motor, how it works?

Torque motors are generally PMSM motors. A high torque motor is toroid shaped, like a donut, and thus has a large diameter and short axis. These motors can directly drive the application without additional mechanics, like worm wheels, belts or pulleys.

High torque motors can be fitted with a closed loop control mechanism, like conventional servomotors, but the concept and shape is different. Because of the shape, the torquemotor generates a lot of torque, but its RPM is limited. A conventional servomotor on the other hand, can reach much higher RPM but generates far less torque. It is therefore often fitted with a gearbox to reach the desired speed to torque ratio, but this gearing does reduce efficiency and accuracy.

Direct Drive Technology

In direct drive torque motors, the motor directly drives the load which eliminates the use of a transmission or a gearbox. As a result, the amount of moving parts in the system is reduced tremendously increasing the efficiency and creating a quiet and high dynamic operation. Therefore, direct drive technology achieves a very high lifetime. Direct drive motors are ideal for applications where a high positioning accuracy is needed and small size, low weight, minimum power and optimal speed control is desired.

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Compared to brushed motors, the absence of brushes in direct drive motors eliminates mechanical wear. The load is directly driven by the motor. No gearboxes, worm gear drives or other transmissions necessary. This reduces the moving parts in the system, resulting in high operational life and reliability, while reducing overall system costs. Therefore, direct drive torque motors enable cost optimized solutions for your applications.

Axial flux vs radial flux motor

The name ‘radial’ or ‘axial’ originates from the direction in which the permanent magnets impose the magnetic field. When the flux is imposed in the radial direction the motor is called a radial flux motor. When the flux is imposed in the axial direction, it is called an axial flux motor. At Magnetic Innovations we believe strongly in the radial flux high torque motor topology.

The radial flux permanent magnet motor benefits from a far more straightforward construction. This translates into an easier installation and a benefit in cost when it comes to the mechanical construction. The radial flux motors at Magnetic Innovations utilize the outer rotor topology and incorporate a number of optimizations which improve the overall efficiency

Magnetic Flux Path Axial vs Radial Flux Motor

Frameless high torque motor

Frameless refers to a motor without a frame, housing, bearing or feedback system. Our Framless High Torque Motors Series are designed to be built in the integral part of a system. With its outrunner and frameless design, size and weight are decreased making the motors easy to integrate and use in various applications. In addition, because of the high specific torque density, frameless torque motors are very suitable for small building volumes.  

Outrunner vs inrunner torque motors

There are two types of direct drive frameless torque motors: the outrunner and the inrunner torque motors. For an 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. The stator of the outrunner motors 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.

Outrunner torque motor

Inrunner motor

Magnetic Innovations is specialised in the outrunner typology. An advantage of an outrunner motor compared to an inrunner motor, is that the air gap surface is substantially larger. In other words, the surface area through which the electromagnetic field lines pass from rotor to stator, is much larger. This way more electromechanical force is generated.

High torque motor video's

The video’s below show:

    • The stator
    • The rotor 
    • The rotor and stator

The stator of a high torque motor

The stator is the static part of the torque motor, which contains the lam stack and copper wire. Moreover, 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. Further, the copper windings on the stator can be configured in different ways to create different performance parameters that can be important for various applications.

The rotor of a high torque motor

The rotor is the moving or rotating part of the torque motor, which contains the permanent magnets. The permanent magnets are placed on the rotor in a north south north south pattern. The blue and orange areas depict the north and south part, respectively. This is shown in the video to the right. Consequently, the permanent magnetic field of the rotor will interact with the alternating magnetic field of the rotor. Further, between the stator and the rotor the magnetic air gap is located. 

The stator and rotor of a torque motor

In case of an outrunner torque motor, the rotor is put around the stator. As a result, the magnetic field of the stator starts to interact with the permanent magnet field of the rotor. Consequently, the permanent magnetic field of the rotor will start rotating synchronously with the stator magnetic field and torque (N) is created. This is shown in the video to the right. 

The torque of the direct drive torque motor is proportional to the current in the stator. In addition, the required voltage is proportional to the speed. 

    • Input: Electric power = current * voltage. 
    • Output: Mechanical power = torque * angular velocity. 

By adjusting the number of windings and / or winding configuration, the ratio between the voltage and current demand can be adjusted. This makes the motor usable for various application areas, such as semicon, robotics, food and packaging. 

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