Siemens SINAMICS S120 Function Manual page 135

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Commissioning U/f control

Before commissioning the U/f control, observe the following information:

The run-up at the current limit (p0640) permits a quick run-up of the drive, e.g. when operating

the drive with variable moments of inertia. Only the ramp-function generator stops when the

current limit (p0640) is reached. This does not prevent the current from increasing even further.

In view of this, the parameters you assign must include a safety margin relative to the current

limits for the monitoring functions to prevent the drive from switching off with an overcurrent

To commission the U/f control, proceed as follows:

1. Check the requirements for U/f control.

– Initial commissioning has been performed:

– Initial commissioning has not been performed:

2. Set the rated motor speed via parameter p0311.

3. Activate U/f control with the parameter setting of p1317 = 1.

Automatic activation of additional functions

With p1317 = 1, the following functions are also activated automatically:

● Resonance damping (p1338)

● Vdc controller (p1240, p1244, p1248, p1250)

● Limitation of the up ramp as a result of M, P and I limits

● The ramp-function generator is stopped as soon as the current limit p0640 is exceeded.

4. Issue the enable signals for operation.

5. Enter the speed setpoint.

Drive functions

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

The parameters for U/f control have been preset with appropriate values.

The following relevant motor data must be checked and corrected:

r0313 Motor pole pair number, actual (or calculated)

p0314 motor pole pair number

p1318 U/f control ramp-up/ramp-down time

p1319 U/f control voltage at zero frequency

p1326 U/f control programmable characteristic frequency 4

p1327 U/f control programmable characteristic voltage 4

p1338[0...n] U/f mode resonance damping gain

p1339[0...n] U/f mode resonance damping filter time constant

p1349[0...n] U/f mode resonance damping maximum frequency

In order to obtain a pure diagnostic mode without any influence on actual values, the

resonance damping must be deactivated (p1338 = 0).

Servo control

5.12 U/f control