Siemens SINAMICS G150 Operating Instructions Manual page 390

Setpoint channel and closed-loop control
7.4 Vector speed/torque control with/without encoder
Active loads
Active loads, which can reverse the drive, e.g. hoisting gear, must be started in the open-
loop speed control mode. In this case, bit p1750.6 must be set to 0 (open-loop controlled
operation when the motor is blocked). The static (steady state) torque setpoint (p1610) must
be greater than the maximum occurring load torque.
Note
Loads that can drive the motor
For applications with high regenerative load torques at low speeds, p1750.7 can also be set
to 1 As a result, the speed changeover limits of the motor model are increased and a faster
changeover can be made into open-loop controlled operation.
Permanent-magnet synchronous motors
Standard procedure: open-loop controlled operation at low speeds
Normally, permanent-magnet synchronous motors are started and reversed in open-loop
controlled operation. The changeover speeds are set to 10% or 5% of the rated motor
speed. Changeover is not subject to any time condition (p1758 is not evaluated). Prevailing
load torques (motor or regenerative) are adapted in open-loop operation, facilitating
constant-torque crossover to closed-loop operation even under high static loads. Whenever
the pulses are enabled, the rotor position is identified.
Figure 7-12 Zero crossing in open-loop controlled operation at low speeds
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Converter cabinet units
Operating Instructions, 03/2012, A5E03263466A