BECKHOFF AL2000 - Manual (Page 6)

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line. Now this magnet is positioned above two fixed magnets as shown left in the figure. Because of the attract-
ing and repelling forces, it will move towards the magnet with the opposite pole pointing upwards. The move-
ment stops when the magnet is positioned right on top of it. Changing the poles of the upper magnet, would
make the magnet move back to the right.
Physical resemblance of permanent magnet and electric coil:
A linear motor is propelled by similar attraction and repulsion forces. The changing the magnetical poles is en-
abled by using winded cupperwire, i.e. a coil, in stead of a permanent magnet.
It is known that a metal wire, winded around a core and conducting een electric current, acts like a magnet.
Among others, the produced magnetic force of an electric coil depends on
1. the amperage of the current,
2. the number of windings, and
3. the kind of core material.
Electromagnetic exiting of a constant and a commutating magnetic field:
Generally iron is used as core material. Because of its very low magnetic resistance it has some very good
characteristics for conducting the magnetic field. In fact the iron core can be considered as a magnet. In the
case of a direct current the core behaves like a permanent magnet. In addition, reversing the phase of the cur-
rent makes the magnetic poles switch. So an alternating current excites a commutating magnetic field.