Siemens 7SK80 - Page 130

Functions
2.7 Motor Protection (Motor Starting Protection 48, Motor Restart Inhibit 66, Load Jam Protection)
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
130
Figure 2-37 Logic diagram of the Motor Starting Protection
Switching of Startup Times
The motor manufacturer provides startup time curves for both cold and warm motor conditions (see Figure 2-
36). The function Motor Starting Protection automatically performs a switching. The "warm motor" condition is
derived from the thermal storage of the restart inhibit (see Section 2.7.2). Therefore, this function must be en-
abled. The condition for the switching is determined by the parameter 4106 TEMP.COLD MOTOR. If the motor
temperature (actually the rotor temperature) exceeds the threshold value, then a switching from "cold motor"
to "warm motor" takes place (see logic diagram 2-37). The threshold values can be derived from the permitted
number of cold (n
cold
) and warm (n
warm
) motor startups. By means of the following formula an approximate limit
value can be determined.
(Parameter 4106 TEMP.COLD MOTOR)
The setting value should always be lower than the limit value (see Setting Notes 2.7.1.2).