72 Planning the electrical installationSize the fuses at the distribution board according to instructions given in chapterTechnical data. The fuses will protect the input cable in short-circuit situations, restrictdrive damage and prevent damage to adjoining equipment in case of a short-circuitinside the drive.Note: Circuit breakers must not be used without fuses. For more information, contactABB. Protecting the motor and motor cable in short-circuitsThe drive protects the motor cable and motor in a short-circuit situation when themotor cable is sized according to the nominal current of the drive. No additionalprotection devices are needed. Protecting the drive and the input power and motor cables againstthermal overloadThe drive protects itself and the input and motor cables against thermal overloadwhen the cables are sized according to the nominal current of the drive. No additionalthermal protection devices are needed.WARNING! If the drive is connected to multiple motors, use a separate circuitbreaker 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 toan overload in one motor circuit only Protecting the motor against thermal overloadAccording to regulations, the motor must be protected against thermal overload andthe current must be switched off when overload is detected. The drive includes amotor thermal protection function that protects the motor and switches off the currentwhen necessary. Depending on a drive parameter value, the function either monitorsa calculated temperature value (based on a motor thermal model) or an actualtemperature indication given by motor temperature sensors. The user can tune thethermal 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, andthe connection and use of the temperature sensors.
