Planning the electrical installation 47 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. It is also possible to connect a motor temperature measurement tothe drive. The user can tune both the thermal model and the temperaturemeasurement function further by parameters.The most common temperature sensors are:• motor sizes IEC 180…225: thermal switch (for example Klixon)• motor sizes IEC 200…250 and larger: PTC or Pt100.For more information on the thermal model, see section Motor thermal protection onpage 148. For more information on the temperature measurement function, seesection Motor temperature measurement through the standard I/O on page 157.Implementing the Safe torque off (STO) functionSee Appendix: Safe torque off (STO) on page 417.Using residual current devices (RCD) with the driveACS355-01x drives are suitable to be used with residual current devices of Type A,ACS355-03x drives with residual current devices of Type B. For ACS355-03x drives,other measures for protection in case of direct or indirect contact, such as separationfrom the environment by double or reinforced insulation or isolation from the supplysystem by a transformer, can also be applied.Using a safety switch between the drive and the motorIt is recommended to install a safety switch between the permanent magnetsynchronous motor and the drive output. This is needed to isolate the motor from thedrive during maintenance work on the drive.Implementing a bypass connectionWARNING! Never connect the supply power to the drive output terminals U2,V2 and W2. Power line voltage applied to the output can result in permanentdamage to the drive.If frequent bypassing is required, employ mechanically connected switches orcontactors to ensure that the motor terminals are not connected to the AC power lineand drive output terminals simultaneously.
