What Is a Magnetic Coupler?

B. Leslie Baird

A magnetic coupler transmits a force without any actual physical contact. Since magnetic forces attract and repel, and this force performs work, the action can be linear or rotary. A simple magnetic coupler has a follower and a driver. The driver is connected to a motor, while the follower reacts to the driver's motion, and this results in the transmission of mechanical energy without contact.

Woman holding a book
Woman holding a book

To understand a magnetic coupler, it is helpful to understand magnets. A magnet produces a magnetic field or force. This force acts on ferromagnetic materials and pulls them together or pushes them apart. Ferromagnetic materials include iron, cobalt, nickel, and certain alloys. The overall strength of a magnet is measured by what is termed its magnetic moment, or by the magnetic flux that is produced.

Permanent magnets are made from materials that have their own constant magnetic field. Similarly, electromagnets are created by coils of wire that become magnetic when current runs through the wire. Both of these only have a magnetic force when electricity is applied. The strength of these magnets can be increased by wrapping the coil of wire around a ferromagnetic material. When a change in current in one conductor induces a voltage in the second conductor, both are magnetically coupled.

In a rotary drive motor, a magnetic coupler consists of an inner and outer drive. The movement of one drive provides the magnetic force to turn the other. The outer drive is usually referred to as the driver. The inner drive is the follower and this is usually connected to a pump or other device. This radial design is similar to an electric motor.

Drive pumps that are used for corrosive, flammable, or toxic liquids are often operated with a magnetic coupler. Permanent magnets are used and these can be sealed so that they do not come into contact with the liquid. Rotors are held together by the magnetic force and will not slip during rotation. If too much external force is applied, however, the magnets will separate and the drive pump will stop.

One of the advantages of a magnetic coupler is a reduction in vibration. It can also allow for a separation barrier between the follower and driver since force can be transmitted even if the driver and follower are in separate environments. Alignment is not critical because the magnetic force will still work. The coupling can also work along an axis providing a linear force.

An additional benefit of a motor working with a magnetic coupler is the reduction of contact between moving parts. Instead of direct contact, there is an air gap between the motor and the load it is driving. This reduces friction and can increase the efficiency. It also reduces wear and tear on the motor, which may increase its life. Magnetic coupling may also be referred to as a torque coupling.

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