Functions
2.8 Motor Protection
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
164
Threshold Values "cold" / "warm" Motor
Parameter 4106 TEMP.COLD MOTOR determines the threshold value. It is derived from the number of cold
(n
cold
) and warm (n
warm
) motor startups.
Unless specified otherwise, three cold and two warm startups (n
cold
= 3; n
warm
= 2) will be sufficient. These are
typical motor data. The limit value is thus derived:
A recommended setting value with consideration of a safety margin for TEMP.COLD MOTOR = 25%.
Should the technical data of the motor make reference to four cold and two warm startups (n
cold
= 4; n
warm
= 2),
the following limit value can be determined:
The setting value should fall below the limit value. A value of 40% is recommended for that purpose.
Note
Overload protection curves are also effective during motor starting conditions. However, the thermal profile
during motor starting is constant. Parameter I MOTOR START at address 1107 limits the working range of the
overload protection to larger current values.
Note
The motor restart inhibit 4301 FCT 66 must be switched on to enable distinguishing between cold and warm
condition of the motor.
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