ABB ACS850-04 series, Hardware Manual

Page: 63 / 164

Planning the electrical installation
63
Protecting the drive and the input power and motor cables against thermal
overload
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, use a separate circuit
breaker 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 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, eg, 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 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 is not a personal safety
or a fire protection feature. The ground fault protective function can be disabled with
a parameter, refer to the firmware manual.
Measures for protection in case of direct or indirect contact, such as separation from
the environment by double or reinforced insulation or isolation from the supply
system by a transformer, can be applied.
Residual current device compatibility
The drive is suitable to be used with residual current devices of Type B.
Note: The EMC filter of the drive includes capacitors connected between the main
circuit and the frame. These capacitors and long motor cables increase the ground
leakage current and may cause fault current circuit breakers to function.