Note:
• Consult the motor manufacturer before using a motor with nominal voltage that
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 to the drive output voltage.
￭ 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.
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.
￭ Requirements tables
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 75
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