Siemens SIMATIC S5 Manual page 280

Start-Up
Testing the encoder's direction of rotation
C A U T I O N :
If the encoder rotates in the wrong direction, there is direct feedback from the
position control loop (the CLC is on). As a result, the drive, instead of stopping,
traverses at maximum speed. You must therefore make sure that the drive can
be immediately stopped via external switches whenever necessary while per-
forming this test. Should the drive begin to oscillate when it is at zero speed,
you must reduce the gain (Kv) factor!
The IP 266 monitors the position control direction, aborting the current operation
with an error message when an error occurs and starting mode 4.
When the IP detects the correct sense of rotation, it disables the monitor; the
monitor remains disabled until mode 4 is once again started. When mode 4 is
terminated, the position control direction is again monitored.
Please note:
A forward traversing movement always means a movement in the direction of
the software end limit switch, whose coordinate position must be higher than
that of the software start limit switch. The IP 266 generates a positive output
voltage (setpoint speed). The incremental encoder must be connected to the IP in
such a way that the resulting direction of rotation causes the IP's counter to
function as an up counter. The IP's counter counts up when the A signal is
detected before the B signal. The opposite is true in the event of a reverse
traversing movement.
As regards the direction of rotation of the encoder and the motor, the con-
ventions are the same for linear and rotary axes. A clockwise (or forward)
traversing movement always means a positive output voltage (setpoint speed), a
counter-clockwise (or reverse) traversing movement a negative output voltage.
When the axis traverses in a clockwise direction, the IP's counter must count up. A
forward movement moves the axis toward the end of the traversing range,
which, in the case of a rotary axis, is the same as the start of the traversing range,
but which must always be more positive than the latter.
8-14
IP 266
EWA 4NEB 812 6057-02