Setting Notes - Siemens siprotec SJ62 User Manual

2 Functions
2.8.2.2

Setting Notes

General
Characteristic
Values
165
Restart inhibit is only effective and accessible if address 143 48 is set to Enabled. If
not required, this function is set to Disabled. The function can be turned ON or OFF
under address 4301 FCT 66..
Note
When function settings of the restart inhibit are changed, the thermal profile of this
function is reset.
The restart inhibit acts on the starting process of a motor that is shut down. A motor is
considered shut down if its current consumption falls below the settable threshold 212
BkrClosed I MIN. Therefore, this threshold must set lower than the motor idle cur-
rent.
Many of the variables needed to calculate the rotor temperature are supplied by the
motor manufacturer. Among these variables are the starting current I
nominal motor current I
(address 4303), the number of allowable starts from cold conditions (n
number of allowable starts from warm conditions (n
The starting current is entered at address 4302 IStart/IMOTnom , expressed as a
multiple of nominal motor current. In contrast, the nominal motor current is entered as
a secondary value, directly in amperes, at address 4305 I MOTOR NOMINAL. The
number of warm starts allowed is entered at address 4306 (MAX.WARM STARTS) and
the difference (#COLD-#WARM) between the number of allowable cold and warm starts
is entered at address 4307.
For motors without separate ventilation, the reduced cooling at motor stop can be ac-
counted for by entering the factor Kτ at STOP at address 4308. As soon as the
current no longer exceeds the setting value entered at address 212 BkrClosed I
MIN, motor standstill is detected and the time constant is increased by the extension
factor configured.
If no difference between the time constants is to be used (e.g. externally-ventilated
motors), then the extension factor Kτ at STOP should be set to 1.
The cooling with the motor running is influenced by the extension factor 4309 Kτ at
RUNNING. This factor considers that motor running under load and a stopped motor
do not cool down at the same speed. It becomes effective as soon as the current
exceeds the value set at address 212 BkrClosed I MIN. With Kτ at RUNNING =
1 the heating and the cooling time constant are the same at operating conditions (I >
BkrClosed I MIN).
Example: Motor with the following data:
Nominal Voltage
Nominal current
Startup current
Startup Duration
Allowable Starts with Cold Motor
Allowable Starts with Warm Motor
Current Transformer
, the maximum allowable starting time T START MAX
MOT. NOM
V = 6600 V
Nom
I = 126 A
Nom
I
STARTUP
T
STARTUP
n = 3
cold
n = 2
warm
200 A / 1 A
STARTUP
).
warm
= 624 A
= 8.5 s
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
, the
), and the
cold