Protecting The Motor Insulation And Bearings; Requirements Table - ABB ACS880 Electrical Planning Instructions

Note:
• Consult the motor manufacturer before using a motor whose nominal voltage differs
from the AC line voltage connected to the drive input.
• The voltage peaks at the motor terminals are relative to the supply voltage of the drive,
not the drive output voltage.
• If the motor and drive are not of the same size, consider the operation limits of the drive
control program for the motor nominal voltage and current. See the appropriate
parameters in the firmware manual.
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Protecting the motor insulation and bearings

The drive employs modern IGBT inverter technology. Regardless of frequency, the drive
output comprises pulses of approximately the drive DC bus voltage with a very short rise
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.
du/dt 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 du/dt 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.
Electrical planning guidelines 13