Magnetic Couplings

Magnetic couplings work by transferring torque through magnetic attraction and repulsion, so rotation happens without direct physical contact between shafts. In general, magnetic couplings use either two sets of magnets facing each other or a combination of magnets with conductive or special magnetic materials, depending on whether they are permanent magnet, eddy current, or hysteresis types.

As the driver rotates, its magnetic field interacts with the follower, causing it to turn and transmitting torque across the air gap. High-performance magnets such as Neodymium and Samarium Cobalt are commonly used to generate the strong magnetic forces needed for reliable torque transmission.

Magnetic couplings can be classified in several ways. By structural form, magnetic couplings are often divided into tubular and planar types. Based on the type of motion they transmit, they can be linear, rotary, composite, or other special motion types. From the perspective of the coupling principle—how torque is transferred between the driver and follower—magnetic couplings are commonly grouped into synchronous, eddy current, and hysteresis types.

• Synchronous magnetic couplings: Synchronous magnetic couplings create a 1:1 relationship between the motion of the driver and the follower. They work through the attractive and repulsive forces between magnetic poles. An array of alternating North–South permanent magnets is arranged on both the driver and the follower, forming a coupled magnetic circuit where each pole on the driver links to the matching pole on the follower. As the driver rotates or moves, the overlapping poles generate a “push–pull” effect that drives the follower. The resulting force depends on the overlap between poles, the magnetic material used, and the gap between the driver and follower.
• Eddy current magnetic couplings: Eddy current magnetic couplings are asynchronous designs that rely on a speed difference between the driver and follower. In this type, alternating pole permanent magnets are mounted on either the driver or follower, while the mating component is made from an electrically conductive material, typically aluminum or copper. When the driver moves relative to the follower, eddy currents are induced in the conductive part, creating a magnetic field that opposes the field of the permanent magnets. This interaction generates torque and couples the two components. The force produced depends mainly on the magnetic field strength and the speed difference between driver and follower.
• Hysteresis magnetic couplings: Hysteresis magnetic couplings are usually used in asynchronous mode as torque limiters, but they can also operate synchronously. An array of alternating pole permanent magnets is mounted on either the driver or the follower, while the mating component is made from a special material such as Hysterloy, which can be magnetized and demagnetized. At rest, the permanent magnet array magnetizes the Hysterloy, creating a synchronously coupled magnetic circuit. If the available torque is sufficient, the coupling runs in synchronous mode. When the load exceeds the set level, the hysteresis effect allows controlled slip, providing stable torque transfer and protecting the system against overload conditions.

Magnetic couplings offer several performance and reliability advantages that make them a strong choice for demanding applications:

• Non-contact torque transfer: Torque is transmitted without physical contact between shafts, greatly reducing wear and tear.
• Sealed design: They can maintain a fully sealed environment, making them ideal for handling hazardous or sensitive substances.
• Misalignment tolerance: Magnetic couplings can accommodate slight misalignments, reducing stress on components and supporting smoother operation.
• Reduced maintenance: With fewer parts subject to mechanical failure, maintenance costs are lower and equipment life is extended.
• Leakage prevention: Perfect for applications requiring complete sealing, helping prevent leaks, contamination, or exposure to dangerous media.
• Energy efficiency: The non-contact design reduces friction and energy loss, improving overall efficiency and performance.
• Flexibility in design: Magnetic couplings can be customized for different torque levels, temperatures, and environments, offering versatility across many applications.
• Quiet, smooth operation: They run with minimal noise and vibration, contributing to stable, reliable system performance.