Siemens SINAMICS S120 Function Manual page 116

Vector control
4.1 Sensorless vector control (SLVC)
Figure 4-1
In open-loop operation, the calculated actual speed value is the same as the setpoint value.
For vertical loads and acceleration processes, parameters p1610 (constant torque boost)
and p1611 (acceleration torque boost) must be modified in order to generate 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 synchronous 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:
● Closed-loop operation up to approx. 1 Hz output frequency
● Starting in closed-loop controlled operation (directly after the drive has been energized)
Note
In this case, the speed setpoint upstream of the ramp-function generator must be greater
than (p1755).
116
⎛ ⎞
p 1756
• −
⎜ ⎜ ⎟ ⎟
1
⎝ 100 % ⎠
Switchover conditions for SLVC
(only ASM)
p1758
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Drive Functions