Operating & Mounting instructions – 8 074 143.03/03 – Page 95
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Output-Motor-Filter AMF
Modern frequency inverters are using IGBT power modules, by which it is possible to build compact
and cheap units.
Because of the higher switching frequency it was possible to refine the principe of a pulse-wide
modulated (triggered) output voltage.
Disadvantageous are the high-frequently earth leakage currents caused by the motor cable and it´s
capacitance against earth.
Furthermore the high slew rate (du/dt) causes
couplings to parallel lines and voltage spikes on the motor terminals.
The real effects are depending on several influences:
- A low switching frequency reduces the leakage current and the losses in the choke.
- A screened motor cable
reduces the couplings to parallel lines but increases the leakage current
and the losses in the choke very high.
- A long motor cable
increases the leakage current and the losses in the choke very high.
- The kind of laying the cable
, e.g. under water, increases the leakage current and the losses in the
choke like a screened cable.
By using an output motor filter AMF and paying attention to the cable lenghts in the table, it is possi-
ble to keep the following limits:
Slew rate (du/dt)
≤≤
500 V/µs
Peak voltage (U
Peak
)
≤≤
1000 V
AMF specification
The output-motor-filter AMF can be mounted in any position.
Because of the losses caused by high switching frequencies or high cable lenghts it is recommended
to place the filter above the inverter. In that case it will be forced cooled and the inverters cooling air
will not be preheated.
Due to the magnetic stray field of the AMF filter the recommended minimum distances above
and on the sides must be observed, that means no mounting plates, steel bars, control lines,
electronic
Once the filter has been assembled on an assembly plate, the frequency inverter is fixed using the 4
drill holes on the filter.
The electric connection between the filter and the frequency inverter is then made using the cable
from the filter, whereby the phase-sequence is irrelevant.
The mains connection is provided at the top of the filter, on terminals L1, L2 and L3. To do this, the
PE cable is connected to the provided bolts.
The filters for >pDRIVE< CX have leakage currents >3.5 mA. Therefore, they must be grounded
with a protective conductor of at least 10 mm². (Personal safety!)
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