Do I need to install an overload relay with the soft starter?
Schneider Electric's brand of soft starters ( ATS22 , ATS48 ... etc) have a built in protection relay. It prtects the motor thermally.
The soft starter is factory set to protection class 10.
• This protection class can be modified using tHP parameter in SEt menu.
• The motor thermal state is stored in memory. No estimate of motor cooling is calculated while power of the control part is off.
• An overload alarm is activated if motor thermal state exceeds 110%.
• A thermal trip OLFstops the motor if motor thermal state exceeds 125%.
• If the thermal protection has not been disabled, the thermal trip can be indicated by a relay depending on output assignment.
• After the motor has stopped or the soft starter has been switched off, the thermal state is saved. At next start or switch on, the thermal
protection value is restored.
• If a special motor is used (explosion proof, submersible, etc.), the thermal protection should be provided by PTC probes.