Thermal Overload And Short-Circuit Protection; Thermal Overload Protection Of The Drive And The Input And Motor Cables; Thermal Overload Protection Of The Motor; Sensors - ABB ACS800-04 Hardware Manual

46 Planning the electrical installation

Thermal overload and short-circuit protection

Thermal overload protection of the drive and the input and motor

cables
The drive protects itself and the input and motor cables against thermal overload
when the cables are dimensioned according to the nominal current of the drive. No
additional thermal protection devices are needed.
WARNING! If the drive is connected to multiple motors, a separate thermal
overload switch or a circuit breaker must be used to protect each cable and
motor. These devices may require a separate fuse to cut off the short-
circuit current.

Thermal overload protection of the motor


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 user can
tune the thermal model further by feeding in additional motor and load data.
The most common temperature sensors are:
•
Motor sizes IEC180...225: thermal switch (for example, Klixon)
•
motor sizes IEC200...250 and larger: PTC or Pt100
See the firmware manual for more information on the motor thermal protection, and
the connection and use of the temperature sensors.
Protecting the motor against overload without the thermal model

or temperature sensors
Motor overload protection protects the motor against overload without using the
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 IEC/UL 61800-5-1 standard in
conjunction with IEC/UL 60947-4-1. The standards allow for motor overload
protection without external temperature sensors.
The protection feature of the drive allows the user to specify the class of operation
in the same manner as the overload relays are specified in standards IEC/UL 60947-
4-1 and NEMA ICS 2.
The motor overload protection supports thermal memory retention and speed
sensitivity.
For more information, see the drive firmware manual.