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2 Functions
For the rotor temperature leveling 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 of 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 user's requirements 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 a proper functioning, it is also important that the CT values (address 211), the
power system data (address 1102) and the current threshold for distinction between
standstill and running motor (address 281 BkrClosed I MIN, recommended setting
≈ 0.1 · I/IN Motor) have been set correctly. An overview of the parameters and their
default settings is given in parameter overviews.
Temperature Be-
For better understanding of the above considerations, two of the many possible oper-
haviour during
ating states will be discussed in the following paragraph. The examples use the set-
Changing Operat-
tings indicated above. 3 cold and 2 warm startup attempts have resulted in a restart
ing States
limit of 66.7 %.
The following figure illustrates the temperature behaviour during 2 warm startup at-
tempts. The motor is continuously 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 constant τ
1020 s. The restart inhibit is effective for about 7 min.
Figure 2-55
154
Temperature Behaviour during Two Successive Warm Starts
· Kτ at STOP ≈ 5 · 204 s =
L
7UM61 Manual
C53000-G1176-C127-3
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