Operating instructions

90 Application manual Positioning 04/08
4.8 Monitoring Functions
4.8.1 Travel limits
Bumping into the mechanical stops of a limited travel range can be prevented by:
− Hardware limit switches
− Software limit switches (parameters)
Limit switches can be used in order to protect the machine and to limit the travel
range.
Left mechanical
machine stop
Right mechanical
machine stop
Home position
Pos. SW Limit Switch 1145
Pos. HW Limit Switch
()
clockwise rotation of motor
Neg. HW Limit Switch
(anticlockwise rotation of motor)
Digital input for
Neg. HW Limit Switch 1137 Digital input for Pos. HW Limit Switch 1138
Neg. SW Limit Switch 1146
Note: The software limit switches are active only after a successful homing
operation.
4.8.2 Hardware limit switches
Warning! The position axis must be provided with hardware limit switches. They
prevent bumping into mechanical stops and damaging of the machine.
Hardware limit switches must be arranged mechanically such that, in
the case of an error, there is still sufficient distance left for stopping the
drive.
If the travel range is limited by hardware limit switches only and if they
are evaluated by the frequency inverter, the following must be consid-
ered: Changing the parameter settings of the hardware limit switches,
deactivation of the fault reaction or setting of the fault reaction to
"Warning" may result in the drive not stopping when it reaches the
hardware limit switches.
If high values are adjusted for speed and acceleration, and the system
has a high mass moment of inertia, it may overrun the limit switches
and bump into the mechanical stops of the plant. Do not set excessively
high speed and acceleration values in order to avoid damage.
Test hardware limit switches before commissioning:
− Disconnect drive from load to avoid damage.
− Check evaluation of hardware limit switches.
− Check wiring of hardware limit switches: Neg. HW limit switch on
negative end of travel range for anticlockwise rotation of motor, pos.
HW limit switch on positive end of travel range for clockwise opera-
tion of motor.
Application manual Positioning 04/0890