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Figure 8-3
In open-loop operation, the actual speed value is the same as the setpoint value.
To provide the resulting static or dynamic load torque for suspended loads or acceleration
tasks, modify the following parameters:
● p1610 (constant torque increase)
● p1611 (torque increase)
Vector control without encoder has the following features in the low frequency range:
● Closed-loop operation up to approx. 1 Hz output frequency
● Start-up in closed-loop operation (directly after drive is energized)
● Passes through low frequency range (0 Hz) in closed-loop operation
Closed-loop operation above approx. 1 Hz (p1755) and the ability to start or reverse at 0 Hz
directly in closed-loop operation (p1750) produce the following benefits:
● No switching action within the closed-loop control necessary. This means smooth behavior,
● Stationary speed–torque control up to approx. 1 Hz.
SINAMICS SM150 6SL3845-2NN41-8AD0
Operating Instructions Rev.201908010908 EXAMPLE
Switchover conditions
If p1610 is set to 0%, only the magnetizing current r0331 is impressed. For a value of 100%,
the rated motor current p0305 is impressed.
To ensure that the drive does not stall during acceleration, p1611 can be increased or
acceleration pre-control for the speed controller used. The p1611 increase is also advisable
to ensure that the motor is not subject to thermal overload at low speeds.
Note
In this case, the speed setpoint upstream of the ramp-function generator must be greater
than p1755.
no frequency drops.
Note
For controlled reversing or controlled starting for 0 Hz, under the following condition the
closed-loop control is switched automatically from closed-loop controlled operation to open-
loop controlled operation:
● Dwell-time > 2 seconds or > p1758 in the range of 0 Hz
Operation
8.5 Functions
109
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