BECKHOFF AL2000 - Manual (Page 13)

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All these items affect the accuracy of the linear motor, its small signal behaviour.
SERVOCONTROLLER
Linear motors of the AL2000 series could ideally be combined with our 3 Phase servocontrollers of the AX2000
series. The servocontroller AX2000 covers the complete rotary and linear motor range. The prepared motor-,
feedback- and thermal-protection cables completes the full linear motor servo system. All default parameters of
linear motor-controller combinations are defined and loadable.
BRAKING AND DAMPING
High velocities are gained at short distances. In normal conditions dynamic braking is provided by a reversed
electromagnetic force. However, for short runouts braking and damping could be necessary. In certain condi-
tions, for instance a loss of electrical power, this could be critical for safety.
MAGNETIC FLUX AND DISTANCE
Just like a rotary motor a linear motor is propagated by an electromagnetical force. Magnets produce a so
called magnetic flux, which can be considered as the density of the magnetic field. This counts for the perma-
nent magnet as well as the electromagnetic coil. The magnetic field is densest in the direct vicinity of the mag-
netic pole, typically several thousand Gauss. This flux usually diminishes rapidly when measured at some cen-
timeters from the magnet pole. Since the magnetic force depends directly on the magnetic flux, it is important to
keep the gap between coil unit and magnetplate small. The gap can vary a little without loosing much perform-
ance.
COGGING
The permanent magnets produce an attraction force to all magnetic materials in the vicinty. When the coil unit
contains such materials, f.i. the iron core, the motorforce could be influenced. Because of the separate position-
ing of the magnets on the magnetplate, the magnetic field is not homogenous. So, dependent of the position of
the magnets the motorforce will be disturbed. Such position dependent disturbance could make the slide cog.
Beckhoff Industrie Elektronik sophisticated design meets with the problems of cogging.
CAREFUL INSTALLATION
Installing a linear motor should be done very cautious. Read the installation manual carefully. Installation only
by qualified personal. Special attention should be given to the strong magnetic field in the vicinity of the mag-
netplates. These plates should be handled with care and with proper tools. Beware of the fact that materials or
clothes get jammed between magnetplate and iron objects. For mounting and dismounting purposes magnetic
field neutralizing protectionplates are to be used. Carefully follow the installation instructions of the applied
servo controller ans linear encoder. Electronic wiring, such as the sensor cable, should be shielded or com-
bined to twisted pairs in order to reduce the influence of EMI.