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6.3 Motor filter
Advantages of using a motor filter:
• The motor filter reduces capacitive currents caused by parasitic
cable capacitances.
• The slope of the motor voltage (dv/dt) is limited to 500 V/µs.
Motor filters are always required for:
• unscreened cables longer than 100m.
• screened cables longer than 50m.
• when using motors which do not have suitable insulation for
inverter operation. (Observe data of the motor manufacturer.)
Please note:
• Install the motor filter as close as possible to the inverter
- Maximum cable length 5 m
• Connect +U
G
and -U
G
of the motor filter only to the inverter
terminals of the same designation.
• Select the control mode "V/f characteristic control"
(C006 = -0-). The control "magnetizing current control" is not
permissible.
• The chopping frequency must be at least 4 kHz.
• The max. permissible output frequency is 300 Hz.
• The inverter is loaded in addition to the motor current with
approx. 12% of the rated filter current.
• The voltage drop across the motor filter at rated current and
rated frequency (f
d
= 50 Hz) is 2 to 3% of the inverter output
voltage.
• For motor cable lengths > 100 m (screened) and > 200 m (un-
screened) a motor supply filter should be used.
• With unscreened motor cables it should be tested whether the
system complies with the interference levels required for the CE-
EMC conformity.
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