Setting Notes - Siemens siprotec SJ62 User Manual

2 Functions
2.8.1.2

Setting Notes

General
Startup Parameter
157
Motor starting protection is only effective and accessible if address 141 48 = Enabled
is set. If the function is not required Disabled is set. The function can be turned ON
or OFF under address 4101 48.
The device is informed of the startup current values under normal conditions at
address 4102 STARTUP CURRENT, the startup time at address 4103 STARTUP
TIME. At all times this enables timely tripping if the value I
device is exceeded.
If the startup time is longer than the permissible blocked rotor time, an external rpm-
counter can initiate the definite-time tripping element via binary input („>Rotor
locked"). A locked rotor leads to a loss of ventilation and therefore to a reduced
thermal load capacity of the machine. For this reason the motor starting time monitor
must issue a tripping command before reaching the thermal tripping characteristic
valid for normal operation.
A current above the threshold I MOTOR START (address 1107) is interpreted as a
motor startup. Consequently, this value must be selected such that under all load and
voltage conditions during motor startup the actual startup current safely exceeds the
setting, but stays below the setting in case of permissible, momentary overload.
Example: Motor with the following data:
Rated Voltage
Nominal Current
Startup Current (primary)
Long-Term Current Rating
Startup Duration
Current Transformers
The setting for address STARTUP CURRENT (I
lated as follows:
For reduced voltage, the startup current is also reduced almost linearly. At 80 %
nominal voltage, the startup current in this example is reduced to 0.8 · I
The setting for detection of a motor startup must lie above the maximum load current
and below the minimum start-up current. If no other influencing factors are present
(peak loads), the value for motor startup I MOTOR START set at address 1107 may
be an average value:
2
t calculated in the protection
V = 6600 V
Nom
I = 126 A
Nom
= 624 A
I
STARTUP
= 135 A
I
max
T = 8.5 s
STARTUP
I /I = 200 A /
Nom CTprim Nom CTsec
1 A
) as a secondary value is calcu-
STARTUP
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
= 2.5.
STARTUP