A magnetic coupling is a

coupling A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end mov ...

that transfers torque from one shaft to another, but using a magnetic field rather than a physical mechanical connection. Magnetic shaft couplings are most often used for liquid pumps and propeller systems, since a static, physical barrier can be placed between the two shafts to separate the fluid from the motor operating in air. Magnetic shaft couplings preclude the use of shaft seals, which eventually wear out and fail from the sliding of two surfaces against each another. Magnetic couplings are also used for ease of maintenance on systems that typically require precision alignment, when physical shaft couplings are used, since they allow a greater off axis error between the motor and driven shaft.

Applications

Some

diver propulsion vehicle A diver propulsion vehicle (DPV), also known as an underwater propulsion vehicle, sea scooter, underwater scooter, or swimmer delivery vehicle (SDV) by armed forces, is an item of diving equipment used by scuba divers to increase range underw ...

s and

remotely operated underwater vehicle A remotely operated underwater vehicle (technically ROUV or just ROV) is a tethered underwater mobile device, commonly called ''underwater robot''. Definition This meaning is different from remote control vehicles operating on land or in the ai ...

s use magnetic coupling to transfer torque from the electric motor to the prop. Magnetic gearing is also being explored for use in utility scale wind turbines as a means of enhancing reliability. The magnetic coupling has several advantages over a traditional

stuffing box A stuffing box or gland package is an assembly which is used to house a gland seal. It is used to prevent leakage of fluid, such as water or steam, between sliding or turning parts of machine elements. Components A stuffing box of a sailing boat ...

. Some aquarium pumps are magnetic drive pumps -- they use magnetic coupling between the motor on the dry side of an aquarium wall and the propeller/impeller in the water on the other side of that aquarium wall. With two face-to-face magnetized disks -- one driving magnet on the dry side, and another driven magnet on the wet side of the glass -- there are two options for designing the magnetic pattern on each disk. One option balances the (attractive) section that transfers torque, with magnetic repulsion near the axis, to nearly cancel out axial load. The other option designs the magnetic pattern to maximize the torque, and uses a mechanical

thrust bearing A thrust bearing is a particular type of rotary bearing. Like other bearings they permanently rotate between parts, but they are designed to support a predominantly axial load. Thrust bearings come in several varieties. *''Thrust ball bearings ...

to resist the attraction between the magnetized disks. A

magnetic stirrer A magnetic stirrer or magnetic mixer is a laboratory device that employs a rotating magnetic field to cause a stir bar (or ''flea'') immersed in a liquid to spin very quickly, thus stirring it. The rotating field may be created either by a rota ...

is another example of magnetic coupling. Magnetic couplings are often synchronous (output shaft speed equals input shaft speed, or 1:1). The first few gears in the geartrain of an Omega Megasonic wristwatch have no teeth; instead magnetic north and south poles on neighboring gears act like the teeth and trough of neighboring spur gears, as each gear drives the next gear in the chain. Such magnetic gears, like spur gears, always have gear ratios as the ratios of small integers. More sophisticated magnetic gearing uses pole pieces to modulate the magnetic field; they can be designed to have gear ratios from 1.01:1 to 1000:1.

Feature

There lots of features about the magnetic coupling.

No vibration

It can avoid the transmission of vibration and realize the smooth operation of the working machine. There is no contact between the active part and the driven part, and there is no rigid connection problem. One part will not be directly transmitted to another part when there is a sudden change or vibration.

Overload protection

It can realize overload protection during the operation of working machinery. When the load of the driven part increases suddenly and the overload is too large, the two parts may slip out. and end The transmission of torque avoids the danger of the follower being easily damaged when it does not work normally and also protects the motor.

Easy maintain

The magnetic coupling transmission device is relatively simple in structure, and there is a gap between the driving part and the driven part, which is easy to install, disassemble and maintain.

Easy transmit power

When the magnetic coupling transmits power, it can perform linear motion, rotary motion, and helical compound motion that combines linear motion and rotary motion; the combination of magnetic coupling transmission and different mechanical structure designs can realize orderly motion in three-dimensional space, and some other differences. Movement in a certain way or displacement at a certain distance and directional movement at any angle of rotation.

Green development

It is developed by applying magnetic coupling transmission technology in the production process of petroleum, chemical, pharmaceutical, offshore oil well operations, non-ferrous metal smelting, wet mineral processing, food and other industries. The Magnetic coupling pump can completely avoid the leakage of corrosive media such as toxic, harmful, flammable, explosive, strong acid, strong alkali, etc..

References

{{Reflist, colwidth=35em Magnetic devices Rotating shaft couplings