Siemens siprotec SJ62 User Manual page 168

Temperature Be-
haviour during
Changing Operat-
ing States
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
2.8 Motor Protection (Motor Starting Protection 48, Motor Restart Inhibit 66)
The following settings are derived from these data:
The following settings are made:
IStart/IMOTnom = 4.9
I MOTOR NOMINAL = 0.6 A
T START MAX = 8.5 s
MAX.WARM STARTS = 2
#COLD-#WARM = 1
For the rotor temperature equilibrium time (address 4304), a setting of. T Equal =
1 min has proven to be a good value. The value for the minimum inhibit time T MIN.
INHIBIT depends on the requirements set by the motor manufacturer, or by the
system conditions. It must in any case be higher than 4304 T Equal. In this example,
a value was chosen that reflects the thermal profile (T MIN. INHIBIT = 6.0 min).
The motor manufacturer's, or the requirements also determine also the extension
factor for the time constant during cool-down, especially with the motor stopped.
Where no other specifications are made, the following settings are recommended: Kτ
at STOP = 5 and Kτ at RUNNING = 2.
For a proper functioning, it is also important that the CT values and the current thresh-
old for distinction between stopped and running motor (address 212 BkrClosed I
MIN, recommended setting ≈ 0.1 I
rameters and their default settings is generally given in the setting tables.
For a better understanding of the above considerations several possible operating
ranges in two different operating areas will be discussed in the following paragraph.
Settings indicated above are to be used prevaling 3 cold and 2 warm startup attempts
have resulted in the restart limit reaching 66.7%.
A. Below the thermal restarting limit:
1. A normal startup brings the machine into a temperature range below the thermal
restarting limit and the machine is stopped. The stop launches the equilibrium time
4304 T Equal and generates the message „66 TRIP". The equilibrium time
expires and the message „66 TRIP" is cleared. During the time T Equal the
thermal model remains "frozen" (see Figure 2-54, to the left).
2. A normal startup brings the machine into a temperature range below the thermal
restarting limit, the machine is stopped and is started by an emergency startup
without waiting for expiry of the equilibrium time. The equilibrium time is reset and
the thermal profile is released and „66 TRIP" is reported to be cleared (see
Figure 2-54, to the right).
) have been set correctly. An overview of pa-
MOT.NOM
166