Functions
2.37 Restart Inhibit for Motors (ANSI 66, 49Rotor)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
260
The following settings are made:
IStart/IMOTnom . = 4.9
T START MAX . = 8.5 sec
MAX.WARM STARTS . = 2
#COLD-#WARM . = 1
For the rotor temperature equilibrium time, a setting of approx. T EQUAL = 1.0 min has proven to be a practical
value. The value for the minimum inhibit time T MIN. INHIBIT depends on the requirements set by the motor
manufacturer, or on the system conditions. It must in any case exceed T EQUAL. In this example, a value has
been chosen that roughly reflects the thermal profile (T MIN. INHIBIT =6.0 min).
The motor manufacturer's or the user's requirements also determine the extension factor for the time constant
during cooldown, especially for motor standstill. Where no other specifications are made, the following settings
are recommended: Kτ at STOP = 5.0 and Kτ at RUNNING = 2.0 .
For proper functioning it is also important that the CT values for side 2 (addresses 211 and 212), the power
system data (addresses 251, 252) and the current threshold for distinction between stopped and running motor
(address 281 BkrClosed I MIN, recommended setting ≈ 0.1 · I/I
Mot.Nom.
) were set correctly. An overview of
the parameters and their default settings is given in the settings list.
Temperature Behaviour during Changing Operating States
For better understanding of the above considerations, two of the many possible operating states will be dis-
cussed in the following paragraph. The examples use the settings indicated above. 3 cold and 2 warm startup
attempts have resulted in a restart limit of 66.7 %.
The following figure illustrates the temperature behaviour during 2 warm startup attempts. The motor is contin-
uously operated at nominal current. After the first switchoff T EQUAL is effective. 30 s later the motor is restarted
and immediately shut down again. After another pause, the 2nd restart attempt is made. The motor is shut down
once again. During this 2nd startup attempt, the restart limit is exceeded, so that after shutdown the restart
inhibit takes effect. After the temperature leveling time (1 min), the thermal profile cools down with the time con-
stant τ
R
· Kτ at STOP ≈ 5 · 204 s = 1020 s. The restart inhibit is effective for about 7 min.
Figure 2-118 Temperature Behaviour during Two Successive Warm Starts
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