Protecting The Motor Insulation And Bearings; Requirements Table - ABB ACS800 Hardware Manual

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4. Consult the motor manufacturer before using a motor in a drive system where the
motor nominal voltage differs from the AC power source voltage.
5. Ensure that the motor insulation system withstands the maximum peak voltage in
the motor terminals. See the
insulation system and drive filtering.
Example: When the supply voltage is 440 V and the drive is operating in the
motor mode only, the maximum peak voltage in the motor terminals can be
approximated as follows: 440 V · 1.35 · 2 = 1190 V. Check that the motor
insulation system withstands this voltage.

Protecting the motor insulation and bearings

The output of the drive comprises – regardless of output frequency – pulses of
approximately 1.35 times the equivalent mains network voltage with a very short rise
time. This is the case with all drives employing modern IGBT inverter technology.
The voltage of the pulses can be almost double at the motor terminals, depending on
the attenuation and reflection properties of the motor cable and the terminals. This in
turn 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 cause current pulses that flow through the motor bearings, which
can gradually erode the bearing races and rolling elements.
The stress on motor insulation can be avoided by using optional ABB du/dt filters.
du/dt filters also reduce bearing currents.
To avoid damage to motor bearings, the cables must be selected and installed
according to the instructions given in this manual. In addition, insulated N-end (non-
driven end) bearings and output filters from ABB must be used according to the
following table. Two types of filters are used individually or in combinations:
• du/dt filtering (protects motor insulation system and reduces bearing currents).
• common mode filtering (CMF) (mainly reduces bearing currents).

Requirements table

The following table shows how to select the motor insulation system and when an
optional ABB du/dt filter, insulated N-end (non-driven end) motor bearings and ABB
common mode filters are required. The motor manufacturer should be consulted
regarding the construction of the motor insulation and additional requirements for
explosion-safe (EX) motors. Failure of the motor to fulfil the following requirements
or improper installation may shorten the life of the motor or damage the motor
bearings.
Planning the electrical installation
Requirements table below for the required motor