Magnetic Assemblies / Magnetic Couplings
Magnetic Couplings: Non-Contact Torque Across a Sealed Barrier
Magnetic couplings transmit torque without a mechanical shaft seal by synchronizing inner and outer magnet rotors across an air gap or containment can. Torque, slip behavior, eddy-current loss and mechanical containment must be designed together.
Geometry and Dimension Definition
Use functional datums and define the magnetization reference on the drawing. The table below provides the minimum geometry information for a practical manufacturing review.
| Parameter | How to define it | Why it matters |
|---|---|---|
| Coupling OD / ID | Rotor and containment envelope | Defines available magnet volume and radial gap |
| Active length | Axial overlap of magnetic rotors | Controls torque capacity |
| Pole count | Alternating pole pairs and angular reference | Influences torque density and slip behavior |
| Barrier thickness | Containment can material and wall | Adds magnetic gap and may create eddy-current loss |
Design Considerations
Torque curve
Specify working torque, peak torque and allowable slip instead of one nominal value.
Containment can
Electrical conductivity, strength, corrosion resistance and thickness affect both safety and heating.
Thermal conditions
Eddy loss, fluid temperature and poor heat rejection can raise magnet temperature.
Manufacturing and Assembly Notes
- Metallic barriers can overheat at speed due to eddy currents.
- Loss of synchronism may create impact torque or heat.
- Rotor concentricity and bearing deflection change the working gap.
- Chemical exposure must be assessed for the entire wetted system.
Typical Applications
Sealless pumps
Leak-free torque transfer across a containment shell.
Mixers and reactors
Drive through vessel walls.
Vacuum systems
Motion without a dynamic shaft seal.
Instrumentation
Compact isolated rotary transmission.
Engineering Questions
How is coupling torque specified?
Provide operating, start-up and upset torque across the speed and temperature range.
Why does can material matter?
Conductive metal can create eddy-current heating; non-metallic barriers reduce loss but have different strength and compatibility.
What happens during overload?
The rotors may slip out of synchronism. Recovery behavior and thermal consequences should be validated.
Can the design be scaled by adding magnets?
Not linearly. Pole pitch, saturation, gap and rotor dimensions interact.
For a focused design review, share your drawing, operating temperature, air gap, target magnetic performance and annual volume through our enquiry page. You can also return to Magnetic Assemblies for material-level guidance.