Siemens SINAMICS S120 Function Manual page 95

Note
Sensorless operation (without an encoder) is not permitted for vertical axes or
similar. Sensorless operation is also not suitable for a higher-level closed-loop
position control.
The start behavior of synchronous motors from standstill can be improved further
by parameterizing the pole position identification (p1982 = 1).
Behavior once pulses have been canceled
Once the pulses have been canceled in operation without an encoder, the
current actual speed value of the motor can no longer be calculated. Once the pul-
ses are enabled again, the system must search for the actual speed value.
p1400.11 can be used to parameterize whether the search is to begin with the
speed setpoint (p1400.11 = 1) or with speed = 0.0 (p1400.11 = 0).
Under normal circumstances, p1400.11 = 0 because the motor is usually started
from standstill.
If the motor is rotating faster than the changeover speed p1755 when the pulses
are enabled, p1400.11 = 1 must be set.
If the motor is rotating and the start value for the search is as of the setpoint
(p1400.11 = 1), the speed setpoint must be in the same direction as the actual
speed before the pulses can be enabled. A large discrepancy between the actual
and setpoint speed can cause a malfunction.
Warning
!
Once the pulses have been canceled, no information about the motor speed is
available. The computed actual speed value is then set to zero, which means that
all actual speed value messages and output signals are irrelevant.
© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
Operating Modes
Servo control
3-95