External Motor Thermal Overload Protection - Siemens MICROMASTER Vector Operating Instructions Manual

2. INSTALLATION – MICROMASTER Vector

2.2.5 External Motor Thermal Overload Protection

When operated below rated speed, the cooling effect of fans fitted to the motor shaft is reduced. so that most motors require de-rating
for continuous operation at low frequencies. To ensure that motors are protected against overheating under these conditions it is
strongly recommended that a PTC temperature sensor is fitted to the motor and connected to the inverter control terminals as shown
in Figure 2.2.5.
Note: To enable the motor overload protection trip function, set parameter P087=1
14
Inverter Control
MOTOR
Terminals
PTC
15
Figure 2.2.5: Motor Overload PTC Connection.
© Siemens plc 1999
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