Category Archives: Permanent magnets

Magnetic bearings

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Bearing

Bearings are devices which constrains the relative motion of a moving (rotating or translating) part. They also aid in reducing friction. When we think of a bearing we often think of only a mechanical bearing (see image) as it is the most commonly used type of bearing.

Bearings have numerous applications in the field of machine design, automotive, transportation, oil & gas, medical apparatus etc. They are ubiquitous in any device that has motion. In this brief note, I will discuss a bit about a different kind of bearing, Magnetic bearing and highlight its advantages when compared to a mechanical one.

Limitations of mechanical bearings

Mechanical bearings have limited life due to wear and tear and they require lubrication. In many high speed applications they also may need special type of cooling. Nevertheless it is an exhaustible component that needs to be replaced several times during the life of its parent device.

Magnetic bearing

A magnetic bearing facilitates the same functions of a mechanical bearing by employing a magnetic array of permanent magnets. In short there are 2 sets of concentric magnetic arrays which are held in place by the magnetic forces. Since there is no contact there is no wear and tear and technically the magnetic bearing has a very long life.  In addition it can handle very high speeds and large loads with zero friction. This makes a magnetic bearing an excellent choice for machine design, marine, automotive, aerospace and medical devices industry. Recently, there has been a surge in the use of magnetic bearings across various industries. Below is an image of an axial magnetic bearing designed in SoldiWorks. In this design the outer bearing is stationary and the inner bearing is connected to a shaft and is spinning. The weight of the shaft is supported by the magnetic force exerted on the inner bearing.

A magnetic bearing design simulated using EMS for SolidWorks

EMS for SolidWorks helps bearing designers to size their magnetic arrays to support various designs of the shaft (basically different weights). This way the bearing can ensure optimum performance. Another advantage of a magnetic bearing is that it can support offset of the inner cylindrical array wrt to the stationary outer cylinder.

bearing-offset

EMS software can predict accurately the forces acting on the inner bearing for various offset positions.

The magnetic arrangement is assembled according to the figure given below. The N-S directions of each magnet is indicated by the black arrows. This type of arrangement can be easily created in EMS and the magnetic flux distribution and the axial force acting on the inner array can be visualized and computed respectively.

magnetic-directions

magnetic-fluxdistribution

Variation of axial force acting on the inner magnet array with the offset is shown below and is automatically computed by EMS. Note that as the offset increases, so does the axial force but after a point the force reduces. Beyond an offset of 18 mm, the force reverses direction and pulls back the inner array. Using these values of axial force, we can compute the axial magnetic stiffness coefficient

magnetic-flux-final

EMS for SolidWorks

EMS for SolidWorks is the first and only completely embedded Gold Certified software for SolidWorks which helps SolidWorks users study their magnetic, electric and electromagnetic designs seamlessly. It can utilize the geometry created using SolidWorks directly for simulation. Its user interface emulates the SolidWorks and hence there is no learning curve associated with the EMS software for SolidWorks users. Please click here to try out EMS for SolidWorks and see how it helps you design better products. For more information visit www.emworks.com.

 

What is Transient Magnetic Analysis?

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Transient Magnetic, is the study of magnetic fields due to time varying currents, typically caused by surges in currents. Similar to Magnetostatic and AC Magnetic, Maxwell’s displacement current that couples the electric and magnetic fields is assumed to be null.In Transient Magnetic analysis, the Gauss’s law for magnetism, i.e. divergence of magnetic flux density is null, and Faraday’s law,, i.e. the induced electromotive force (emf) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit, are invoked to compute the magnetic field and its related quantities due to permanent magnets and time varying electric currents and voltages. It has many practical applications, including:• Switch on/off modes and failures in power electronic devices
• Saturation in steel cores
• NDT and NDE
• Inductive heating and hardening
• Induction machines
• Levitators
• Motors and generators
• Actuators
• Loud speakers
• Alternators

A Spaceclaim®-embedded Multiphysics Simulation Package

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MONTREAL (September 25, 2014) – EMWorks Inc. announces the launch of its multi-physics simulation package SimClaim which is fully embedded in Ansys SpaceClaim®, formerly SpaceClaim, Engineer®.  Based on the powerful finite element method, SimClaim brings the company’s proven simulation technology to the widest base of mechanical, electrical and electromechanical designers seeking to validate and optimize their electrical, thermal, and structural designs all within the SpaceClaim environment. “We are pleased to have partnered with SpaceClaim to bring this all important multi-physics simulation technology to the SpaceClaim user community. The support we received from SpaceClaim over the last couple of years has been instrumental in accomplishing this important milestone for our company” said Dr. Ammar Kouki, Vice-President of EMWorks. He added “Ansys SpaceClaim®, is an extremely powerful 3D direct modeling software package that eliminates CAD worries for designers. Direct modeling is dramatically different from the traditional CAD software because it allows the user to directly access the model without even knowing its history. SimClaim leverages this power to enable designers and CAE specialists to carry out conceptual analysis inside SpaceClaim in record time without needing to be CAD experts. CAD experts on the other hand, will find that the SpaceClaim-SimClaim combination is hard to beat when it comes to design validation through simulation given the speed and the highly efficient workflow that this combination offers.”

Electromechanical devices in EMS?

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Electromechanical, electromagnetic, and power electronics devices can readily be studied using EMS. Electromagnetic behaviour could also be investigated with EMS. Below is sample list of devices and applications classified by areas:

Electromechanical
• Motors and generators
• Linear and rotational actuators
• Relays
• MEMS
• Magnetic recording heads
• Magnetic levitation
• Solenoids
• Loud speakers
• Electromagnetic Brakes and Clutches
• Alternators
• Magnetic bearings

Electromagnetic
• Coils
• Permanent magnets
• Sensors
• NDT, NDE
• High power
• High voltage
• PCBs
• MRI Magnets
• Induction heating
• Bushings
• Switchgear
• Cables

Power electronics
• Transformers
• Inverters
• Converters
• Bus bars
• Inductors

Electromagnetic behavior
• Insulation studies
• Electrostatic discharge
• Electromagnetic shielding
• EMI/EMC
• Electromagnetic exposure