Computer Drive Installation Instructions

12 Functional Descriptions 08.96

12.33.3 Current setpoint filter

Current setpoint filters (low-pass or bandstop) are used to adapt the speed controller to the

machinery to be controlled.

The amplitude of the speed controller frequency response should remain at 0 dB over the

entire fundamental frequency range.

Note

The frequency response analysis of the current controller does not include the current

setpoint filters. The effects of the filters can be detected only in the frequency response of the

speed controller.

The following measures should be taken when filters are used.

• Record reference frequency response of speed control loop

• Determine points of resonance according to:

No. of resonance points

– Individual pronounced resonance points

– Resonance bundles

Position of resonance points

– Fundamental frequency range

– Controller stability limit

– Frequency range above controller stability limit

Properties

– Distribution of resonance (dependent on traversing speed or direction)

– Mechanical resonance or excessively high controller settings

– Reflected resonance

– Amplitude and phase margins

Note

• Reduce resonance caused by excessively high controller setting by adjusting controller

parameters.

• Use filters only in the case of purely mechanical resonance. If it is possible to attribute

resonance to specific mechanical components of the machine (load vibration, coupling,

etc.), modifications to the machine construction should also be considered.

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SINUMERIK 840C (IA)