Functions
2.37 Restart Inhibit for Motors (ANSI 66, 49Rotor)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
259
2.37.2 Setting Notes
General
Restart inhibit is only effective and available if address 166 RESTART INHIBIT was set to Enabled during
configuration. If the function is not required Disabled is set. Address 6601RESTART INHIBIT serves to
switch the function ON or OFF or to block only the trip command (Block relay).
Required Characteristic Values
Many of the variables needed to calculate the rotor temperature are supplied by the motor manufacturer.
Among these variables are the starting current I
StartCurr
, the nominal motor current I
Mot.Nom
, the maximum allow-
able starting time T START MAX (address 6603), the number of allowable starts from cold conditions (n
cold
),
and the number of allowable starts from warm conditions (n
warm
).
The starting current is entered at address 6602, expressed as a multiple of the nominal motor current
(IStart/IMOTnom). For a correct interpretation of this parameter, it is important that in Power System Data 1
the apparent power (address 252 SN GEN/MOTOR) and the rated voltage (address 251 UN GEN/MOTOR) of
the motor are correctly set. The number of warm starts allowed is entered at address 6606 (MAX.WARM
STARTS) and the difference (#COLD-#WARM) between the number of allowable cold and warm starts is entered
at address 6607.
For motors without separate ventilation, the reduced cooling at motor standstill can be accounted for by enter-
ing at address 6608 the reduced ventilation factor Kτ at STOP. As soon as the current no longer exceeds the
setting value entered at address 281 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.
Cooling with running motor is influenced by the extension factor Kτ at RUNNING. This factor considers that a
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 281 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).
Setting Example:
Example:
Motor with the following data:
The ratio between startup current and motor nominal current is:
Nominal voltage U
N
= 6600 V
Nominal current I
Mot.Nom
= 126 A
Startup current I
StartCurr
= 624 A
Starting time at I
StartCurr
t
Start max
= 8.5 s
Permissible number of startups with cold
motor
n
cold
= 3
Permissible number of startups with warm
motor
n
warm
= 2
Current transformer 200 A / 1 A
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