ABB ACS880-14, Hardware Manual

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time. The pulse voltage can almost double at the motor terminals, depending on the
attenuation and reflection properties of the motor cable and the terminals. This can cause
additional stress on the motor and motor cable insulation.
Modern variable speed drives with their fast rising voltage pulses and high switching
frequencies can generate current pulses that flow through the motor bearings. This can
gradually erode the bearing races and rolling elements.
d u /d t filters protect motor insulation system and reduce bearing currents. Common mode
filters mainly reduce bearing currents. Insulated N-end (non-drive end) bearings protect the
motor bearings.
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Requirements table
These tables show how to select the motor insulation system and when a drive d u /d t and
common mode filters and insulated N-end (non-drive end) motor bearings are required.
Ignoring the requirements or improper installation may shorten motor life or damage the
motor bearings and voids the warranty.
Guidelines for planning the electrical installation 77