ABB ACS880-07XT Series, Hardware Manual

Page: 57 / 168

Guidelines for planning the electrical installation 57
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Protecting the motor insulation and bearings
The drive uses modern IGBT inverter technology. Regardless of frequency, the drive
output has pulses of approximately the drive DC bus voltage with a very short rise time. Up
to twice bus voltage can be at the motor terminals, depending on the attenuation and
reflection properties of the motor cable and the terminals. The increased voltage 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.
Optional d u /d t filters protect motor insulation system and reduce bearing currents. Optional
common mode filters mainly reduce bearing currents. Insulated N-end (non-drive end)
bearings protect the motor bearings.