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Appendix
Data for Transport System Design Calculations
322 MagneMotion
Rockwell Automation Publication MMI-UM007F-EN-P - September 2020
Determining Attractive Force
In addition to the thrust force produced by the QuickStick HT motor, there is an attractive
force between the steel laminations in the stator and the magnet array. This attraction, or
hold-down force, is roughly proportional to the length of magnet array engaged by the stators,
and decreases roughly in an exponential fashion as the gap is increased (see
Figure A-4 ). The
hold-down force is nearly independent of stator current, and thus has the same value whether
or not the stator is powered.
Laboratory measurements of the hold-down force that is obtained with a QuickStick HT
motor at various operational parameter values were used to derive a model that describes the
hold-down force produced.
The model equation describing the hold-down force of a QuickStick HT motor using a high
flux magnet array is:
HDForce (N) = (1850 * EXP
(-0.122 * PhysGap )
) * NumCycles
HDForce (Lb) = ((1850 * EXP
(-0.122 * PhysGap )
) * NumCycles ) / 4.4482
Where:
NumCycles – The length of the array that is engaged by the stators, in cycles (a cycle
for the QuickStick HT is 120 mm).
PhysGap – The distance from the top of the stator to the bottom of the magnet array,
in mm (from 4 mm to 22 mm).
HDForce – The hold-down force that is produced. The hold-down force is indepen-
dent of stator current.