Computer Drive Installation Instructions

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12 Functional Descriptions 08.96

12.33.3 Current setpoint filter

Example of bandstop filter application

The example below explains the basic procedure for applying one or several current setpoint

filters.

Peaks have been measured at 900 Hz and 1200 Hz.

Bandstop filters must be used to dampen both resonant frequencies. The speed controller can

then be set more finely to improve the inadequate dynamic response of the drive.

• Default settings

Filter 1 (activated as standard)

Low pass with fe 2000 Hz and

d 0.7

Reduction of amplitude response well above the fundamental frequency range,

minimization of effects of torque control loop on speed control loop.

• Filters 2 and 3 must be parameterized as the bandstop.

MD 1200: Number of current setpoint filters = 3

MD 1201: Type of current setpoint filter = 6

• Enter frequency.

Filter 2:

MD 1213: Blocking frequency current setpoint filter 2 = 900 Hz

Filter 3:

MD 1216: Blocking frequency current setpoint filter 3 = 1200 Hz

• Enter bandwidth.

Half the measured resonant frequency is recommended as a guide value for the bandwidth

to be entered.

Filter 2:

MD 1213/2 = 900 Hz/ 2 = 450 Hz

MD 1214: Bandwidth current setpoint filter 1 = 450 Hz

Filter 2:

MD 1216/2 = 1200 Hz/ 2 = 600 Hz

MD 1217: Bandwidth current setpoint filter 2 = 600 Hz

• Enter counter bandwidth

Filter 2:

MD 1215: Counter bandwidth current setpoint filter 1 = 0.0 (default)

Filter 3:

MD 1218: Counter bandwidth current setpoint filter 2 = 0.0 (default)

After the filters have been activated, the speed control loop is measured again. The

measurement result indicates whether and to what extent the resonance has been dampened

as a result of the filters. If the signals are now below the 0 dB line, the speed controller

parameters can be adjusted again.

If the measurement results are unsatisfactory, an attempt can be made to improve the effect of

the filters by varying the filter bandwidth (filter 2 MD 1214, filter 3 MD 1217).

Criteria for filter setting:

• Minimum additive phase rotation as a result of "Bandwidth" parameter. Filter effects on

fundamental frequency range are thus minimized.

• Maximum damping effect as a result of pole point compensation (reduce amplitude peak to

between 0 and approximately +3 dB).

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SINUMERIK 840C (IA)