© Siemens plc 1999© Siemens plc 1999
G85139-H1751-U529-D1G85139-H1751-U529-D1
2.2.5 External Motor Thermal Overload Protection2.2.5 External Motor Thermal Overload Protection
When operated below rated speed, the cooling effect of fans fitted to the motor shaft is reduced. so that mostWhen 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 protectedmotors 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 fittedagainst 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.to the motor and connected to the inverter control terminals as shown in Figure 2.2.5.
To enable the motor overload protection trip function, set parameter P087=1To enable the motor overload protection trip function, set parameter P087=1
Inverter ControlInverter Control
Figure 2.2.5: Motor Overload PTC Connection.Figure 2.2.5: Motor Overload PTC Connection.
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