Siemens SINAMICS S120 Function Manual page 123

p1755 [RPM]
p1755 [RPM]
* (1 – p1756)
Open control loop
Closed control loop
Fig. 3-26
In open-loop operation, the calculated actual speed value is the same as the set-
point value. For vertical loads and acceleration, parameters p1610 (constant tor-
que boost) and p1611 (acceleration torque boost) must be modified in order to ge-
nerate the static or dynamic load torque of the drive. If, for induction motors (ASM),
p1610 is set to 0 %, only the magnetizing current r0331 is injected; when the value
is 100 %, the rated motor current p0305 is injected. For permanent-magnet syn-
chronous motors (PEM), for p1610 = 0 %, a pre-control absolute value, derived
from the supplementary torque r1515, remains instead of the magnetizing current
for ASM. To ensure that the drive does not stall during acceleration, p1611 can be
increased or acceleration pre-control for the speed controller can be used. This is
also advisable to ensure that the motor is not subject to thermal overload at low
speeds.
Vector control without a speed sensor has the following characteristics at low
frequencies:
S Closed-loop operation up to approx. 1 Hz output frequency
S Starting in closed-loop controlled operation (directly after the drive has been
energized) (only ASM)
Note
In this case, the speed setpoint upstream of the ramp-function generator must be
greater than (p1755).
© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
⎟ ⎟
f_act
Switchover conditions for SLVC
p1758
Operating Modes
Vector control
t
t
3-123