Torque Setpoint Setting - Siemens SINAMICS S120 Function Manual

Vector control
5.2 Vector control without encoder (SLVC)
5.2.2

Torque setpoint setting

In open-loop operation, the calculated actual speed value is the same as the setpoint value.
For static loads (e.g. for cranes) or during acceleration, you adapt the parameters p1610
(torque setpoint static) and p1611 (additional acceleration torque) to the required maximum
torque. The drive can then generate the static or dynamic load torque that occurs.
● If, for induction motors (ASM), p1610 is set to 0%, then only the magnetizing current
r0331 is impressed.
If 100% is set, the rated motor current p0305 is impressed.
● If, for reluctance motors (RESM) p1610 is set to 0 %, then only the no-load magnetizing
current is impressed.
If 100% is set, the rated motor current p0305 is impressed.
● For permanent-magnet synchronous motors (PMSM), for p1610 = 0%, a precontrol
absolute value, derived from the additional torque r1515, remains instead of the
magnetizing current of the induction motor.
To prevent stalling of the drive during acceleration, the supplementary acceleration torque
p1611 can be increased or acceleration precontrol for the speed controller can be used. This
avoids thermal overloading of the motor at low speeds.
If the moment of inertia of the drive is almost constant, acceleration precontrol with p1496
offers more advantages than the supplementary acceleration torque with p1611. You can
determine the drive moment of inertia using the rotating measurement:
p1900 = 3 and p1960 = 1.
Encoderless vector control has the following characteristics at low frequencies:
● Closed-loop controlled operation for passive loads up to approx. 0 Hz output frequency
(p0500 = 2), for p1750.2 = 1 and p1750.3 = 1.
● Start an induction motor in the closed-loop controlled mode (after the motor has been
completely excited), if the speed setpoint before the ramp-function generator is greater
than p1755.
● Reversing without the need to change into the open-loop controlled mode is possible, if
the range of the changeover speed p1755 is passed through in a shorter time than the
changeover delay time set in p1758, and the speed setpoint in front of the ramp-function
generator lies outside the open-loop controlled speed range of p1755.
● In the "Torque control" mode, at low speeds, the system always changes over into the
open-loop controlled mode.
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Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Drive functions