Motor Protection Functions - Siemens SIRIUS 3RW44 System Manual

6.6

Motor Protection Functions

Motor overload
protection
SIRIUS 3RW44 System Manual
GWA 4NEB 535 2195-02 DS 04
The motor overload protection is based on the motor winding temperature. This
temperature is used to determine whether the motor is overloaded or is
operating within its normal rating.
The winding temperature can either be calculated using the integrated
electronic motor overload function, or be measured using a connected motor
thermistor.
Both versions must be combined (=activated) to obtain the so-called full motor
protection. This combination is recommended for optimum motor protection.
The current flow during motor operation is measured using current measurement
at the converters in the soft starter. The temperature rise of the winding is
calculated on the basis of the configured rated operating current of the motor.
Depending on the set tripping class (CLASS setting) and protection parameters,
a warning or a trip is generated when the characteristic curve is reached.
Device Functions
6-19