www.parkermotion.com
Parker Hannifi n Corporation
Electromechanical Automation Division
3
Engineering
Reference
2.1 Ironcore motors
Ironcore motors consist of a forcer which rides over a single magnet
rail (Fig. 5). The forcer is made of copper windings wrapped around iron
laminations. The back iron provides an effi cient path for the magnetic fl ux
to circulate between the motor and the magnet rail. In addition, there is
an effi cient path for heat to escape the motor. This ironcore design allows
for extremely high forces and effi cient cooling. In fact, the ironcore design
offers the highest force available per unit volume. Finally, the ironcore
design is economically attractive because only one row of magnet
material is required.
One of the drawbacks of the ironcore design is that the motor has a high
attractive force between the forcer and the magnet track. The attractive
force can range from 5 – 13 times the rated force of the motor. This force
must be supported by the bearing system of the motor. In addition, the
high attractive force makes installation more challenging than other linear
motor designs.
Another drawback of the ironcore design is the presence of cogging
forces. Cogging occurs when the iron laminations exert a horizontal force
on the motor in order to line up with their preferred positions over the
magnets. Cogging limits the smoothness of motion systems because
the force generated by the motor must change with position in order to
maintain a constant velocity.
Parker Trilogy has developed a patent-pending Anti-Cog technology that
virtually eliminates cogging and allows ironcore motors to be used in
applications where only ironless motors were considered before. This
offers the machine builder a powerful combination of extremely high
force and smooth operation in an economical package.
To summarize the advantages and disadvantages of ironcore motors:
Ironcore advantages:
•
High Force per Size
- Uses laminations to concentrate the
fl ux fi eld.
• Lower Cost
- Open face design only uses one row of magnets.
•
Good Heat Dissipation
- Because of laminations and large
surface area, heat can be removed easily.
Ironcore disadvantages:
•
Normal attractive force
– 5 to 13 times greater than force
generated.
• Cogging
– Limits the smoothness of motion and creates velocity
ripple.
This is counteracted by Parker Trilogy’s patent pending
Anti-Cog technology.
Fig. 5: Ironcore linear motor
Fig. 7: Parker Trilogy’s TR Series Ironcore Linear Motor Positioner
Fig. 6: Ripped Series Ironcore Linear Motor
Parker Trilogy offers ironcore motors both as components and as
pre-engineered, fully integrated positioning systems. Please refer to the
catalog for the
RIPPED Series
Ironcore Linear Motors and the
TR Series
Ironcore Linear Motor Positioners (Fig. 6 and Fig. 7).
