U/F Control - Siemens SINAMICS S120 Function Manual

5.12

U/f control

Overview
With U/f control, the following components and data can be checked:
● Motor Module
● Power cable between the Motor Module and motor
● Motor
● DRIVE-CLiQ cable between the Motor Module and motor
● Encoder and actual encoder value
The following motors can be operated with U/f control:
● Induction motors
● Synchronous motors
Note
Operating synchronous motors with activated or deactivated resonance damping
● Speed limitation
● Stability
Function description
For U/f control, the drive is operated with an open control loop. In this open-loop control system,
the drive does not require speed feedback and no actual current sensing. The current actual
values only have to be sensed if resonance damping is activated. Operation with U/f control
possible with just a small amount of motor data.
Note
In the U/f mode, the calculated actual speed value is always displayed in r0063. The speed of
the encoder (if installed) is displayed in r0061. If an encoder is not installed, r0061 displays "0".
Drive functions
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
When resonance damping is deactivated, synchronous motors may only be operated
with U/f control up to 25 % of the rated motor speed. If resonance damping is activated,
synchronous motors may be operated with U/f control without any speed limiting.
When resonance damping is deactivated, for synchronous motors, U/f control is only
stable at low speeds. Higher speeds can result in oscillation problems.
When resonance damping is activated, for synchronous motors, U/f control is stable over
the complete speed range. In the default setting, resonance damping is activated with
suitable parameter values; these parameter values can be kept for most applications. If
you become aware of interference caused by a transient response, you have the option
of gradually increasing the value of p1338 in small steps and evaluating how this affects
your system.
Servo control
5.12 U/f control
131