Siemens SINAMICS S120 Function Manual page 96

Operating Modes
Servo control
Switchover between closed-loop/open-loop operation and operation with/without
encoder
Operation without an encoder is activated via parameter setting p1300 = 20.
If p1300 = 20 or p1404 = 0, operation without an encoder is active across the en-
tire speed range. If the speed value is less than the changeover speed p1755, the
motor is operated in accordance with the current/frequency.
During operation with an encoder, a switchover can be made to operation without
an encoder when the speed threshold p1404 is exceeded. If p1404 > 0 and p1404
<p1755, a switchover is not made to operation without an encoder until the speed
exceeds p1755.
Operation without an encoder is displayed in parameter r1407.1.
Without encoder
Open-loop (I/f) / closed-loop
p1300 = 20 or p1404 = 0
Encoder evaluation
p1300 = 21
Mixed operation
p1300 = 21
p1404 > 0
Fig. 3-17 Operation switchovers
Note
In closed-loop control operating mode "Speed controller without encoder", a rotor
position encoder is not required. Since a temperature monitor is not usually
connected in this case either, this must be parameterized via p0600 = 0 (no
sensor).
Series reactor
When special high-speed motors or other low-leakage induction motors are used, a
series reactor may be required to ensure that the current controller remains stable.
The series reactor can be integrated via p0353.
3-96
Open-loop
{
Oper. with encoder
Oper. with encoder
Closed-loop motor model
p1755
Oper. with encoder
Oper. w/out encoder
p1755 p1404
Oper. w/out encoder
p1404 p1755
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© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
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