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Motor Insulation and Drive Output Filter Requirements
for ACS 600 Drives
General
As with all frequency converters employing the most modern IGBT
inverter technology, the ACS 600 output comprises – regardless of
output frequency – pulses of approximately 1.35 times the mains
network voltage with a very short rise time.
The voltage of the pulses can be almost double at the motor terminals,
depending on the motor cable properties. This in turn can cause
additional stress to the motor insulation.
Modern variable speed drives with their fast rising voltage pulses and
high switching frequencies can cause current pulses through the
bearings which can gradually erode the bearing races.
Protecting the Motor
Winding
The stress to motor insulation can be avoided by optional ABB du/dt
filters. du/dt filters also reduce bearing currents.
Protecting the Motor
Bearings
To avoid damage to motor bearings, insulated N (non-driven end)
bearings and output filters from ABB must be used according to the
following table. In addition, the cables must be selected and installed
according to the instructions given in the appropriate Hardware
Manual. Three types of filters are used alone or in combinations:
1. optional ACS 600 du/dt filter (protects motor insulation system and
reduces bearing currents)
2. ACS 600 common mode filter (mainly reduces bearing currents)
3. ACS 600 light common mode filter (mainly reduces bearing
currents).
The common mode filter is composed of toroidal cores installed onto
the motor cable.
Requirements Table
The following table shows how to select the motor insulation system
and when optional ACS 600 du/dt filters, inslulated N (non-driven end)
motor bearings and ACS 600 common mode filters are required. The
motor manufacturer should be consulted regarding the construction of
the motor insulation and additional requirements for explosion-safe
motors. Failure of the motor to fulfil the following requirements or
improper installation may shorten motor life or damage the motor
bearings.
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