Usually, the magnetizing fixture (coil) is specifically designed for the task of the customer and the product.
In the simplest case, only the necessary parameters for the dimensions of the component are calculated for an axial coil, and the device can be designed and manufactured according to standard procedures.
For more difficult tasks, complex FEM calculations taking into account eddy current losses coupled with multipole magnetic structures are required.
Often the field characteristics and the field strengths are validated by FEM calculations already at the quotation stage. This saves you from unpleasant surprises, especially with non-trivial individual designs. And we can guarantee the magnetic result when the order is accepted.
Technically, the magnetic field is generated in all cases by a fast pulse current. The currents used are in the range of 1 kA to 50 kA. The pulse duration is between 50 µsec and 250 msec, depending on the application.
A main aspect regarding the cycle time and lifetime of magnetizing devices is the heating due to the high energies required. Our magnetizing devices are mostly cooled by air. The required air volume is delivered by a side channel compressor. Water cooling is also used for special requirements.
Some examples from previous projects
Fixture for multipole permanent magnet motors
Fixtures for rotors of permanently excited electric motors are usually designed with a back iron.
The magnetization usually takes place at the rotor circumference. The rotors can be designed with a linear or other pole inclination. The magnets can be located on the rotor surface or buried in the rotor laminations.
However, magnetization can also take place axially with multiple poles (disc motors) or from the inside (external rotor motors).
Applications range from micromotors with 4 mm rotor diameter to drive motors for electric and hybrid vehicles and air taxis.
For even larger rotors, such as for ship propulsion, individual poles are magnetized.
Here is an overview of different fixture sizes.
Fixtures for the magnetization of loudspeaker systems
Loudspeaker systems are magnetized either inside an axial fixture or, as in this example, in the stray field of a flat coil arrangement. Eddy current effects must be intensively considered, as these can shield the external field and generate high forces.
Fixture for the magnetization of a displacement sensor for automotive applications
In this device, four systems of a displacement sensor are magnetized simultaneously. A special design shields the carrier parts against parasitic magnetization.
The magnetizing devices are integrated in the automatic line. The cycle time is about 5 sec per part. The handling system is usually projected by partner companies.
Multipole axial fixture
These fixtures are used to magnetize multiple poles on the surface (front) on one or both sides.
Applications are drives (disc rotors), sensors and positioning systems for hard disk drives.
Mostly NdFeB magnets are used. A special requirement is often a narrow pole gap. To achieve short cycle times, several nests can be used in which the components are magnetized in parallel.