￭ Protecting the drive and the power cables against thermal overload
The drive protects itself and the input and motor cables against thermal overload when the
cables are sized according to the nominal current of the drive. No additional thermal protection
devices are needed.
WARNING!
If the drive is connected to multiple motors, use a separate circuit breaker or fuses
for protecting each motor cable and motor against overload. The drive overload
protection is tuned for the total motor load. It may not trip due to an overload in
one motor circuit only.
￭ Protecting the motor against thermal overload
According to regulations, the motor must be protected against thermal overload and the
current must be switched off when overload is detected. The drive includes a motor thermal
protection function that protects the motor and switches off the current when necessary.
Depending on a drive parameter value, the function either monitors a calculated temperature
value (based on a motor thermal model) or an actual temperature indication given by motor
temperature sensors.
The motor thermal protection model supports thermal memory retention and speed sensitivity.
The user can tune the thermal model further by feeding in additional motor and load data.
The most common temperature sensor types are PTC or Pt100.
For more information, see the firmware manual.
￭ Protecting the motor against overload without thermal model or
temperature sensors
Motor overload protection protects the motor against overload without using motor thermal
model or temperature sensors.
Motor overload protection is required and specified by multiple standards including the US
National Electric Code (NEC) and the common UL/IEC 61800-5-1 standard in conjunction
with IEC 60947-4-1. The standards allow for motor overload protection without external
temperature sensors.
The protection feature allows the user to specify the class of operation in the same manner
as the overload relays are specified in standards IEC 60947-4-1 and NEMA ICS 2.
The motor overload protection supports thermal memory retention and speed sensitivity.
For more information, see drive firmware manual.
Protecting the drive against ground faults
The drive is equipped with an internal ground fault protective function to protect the unit
against ground faults in the motor and motor cable. This function is not a personnel safety
or a fire protection feature. See the firmware manual for more information.
An optional ground fault monitoring device (+Q954) is available for IT (ungrounded) systems.
The option includes a ground fault indicator on the drive cabinet door.
￭ Residual current device compatibility
The drive is suitable to be used with residual current devices of Type B.
100 Guidelines for planning the electrical installation
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