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Functions
2.7 Motor Protection (Motor Starting Protection 48, Motor Restart Inhibit 66, Load Jam Protection)
Figure 2-38
Temperature curve at the rotor and in the thermal replica during repeated start-up attempts
Although the heat distribution on the rotor bars may severely differ during motor starting, the different maximum
temperatures in the the rotor are not pertinant for motor restart inhibit (see Figure 2-38). It is much more impor-
tant to establish a thermal replica, after a complete motor start, that is appropriate for the protection of the
motor's thermal condition. Figure 2-38 shows, as an example, the heating processes during repeated motor
starts (three starts from cold operating condition), as well as the thermal replica in the protection relay.
134
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
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