Siemens SIPROTEC 7UM62, Manual

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Restart Inhibit for Motors (ANSI 66, 49Rotor)
221
7UM62 Manual
C53000-G1176-C149-3
RESTART INHIBIT
is used to switch the function
ON
or
OFF
, or to block only the trip
command (
Block Relay
).
Necessary
Characteristic
Values The user communicates to the protective relay the characteristic motor values
supplied by the manufacturer, which are necessary for calculation of the rotor
temperature. These values include the starting current I
Start
, the nominal motor current
I
Mot.nom
, the maximum permissible startup time
T START MAX
(address
6603
), the
number of permissible restart attempts under cold (n
cold
) and (n
warm
) conditions.
The starting current is entered at address
6602
, expressed as a multiple of the nom-
inal 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 cor-
rectly set. The number of warm starts allowed is entered at address
6606
(
MAX.WARM
STARTS
), and the difference between the number of allowable cold and warm starts
(
#COLD-#WARM
) is entered at address
6607
.
For motors without separate ventilation, the reduced cooling at motor stop can be
accounted for by entering at address
6608
the reduced ventilation, expressed by the
factor
K
t at STOP. As soon as the current no longer exceeds the current flow
monitoring setting entered at address
0281 BkrClosed I MIN
, a motor standstill is
assumed and the time constant is increased by the set factor.
If no difference between the time constants is to be used (e.g. externally-ventilated
motors), then the factor should be set to
K
t at STOP =
1
.
The cooling with the motor running is influenced by the extension
K
t 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
0281 BkrClosed I MIN
. With
K
t at RUNNING =
1
the heating and the
cooling time constant are the same at operating conditions (I >
BkrClosed I MIN
).
Setting Example: Motor with the following data:
The ratio between the starting current and the motor nominal current is:
Settings
IStart/IMOTnom
=
4.9
T START MAX
=
8.5 s
MAX.WARM STARTS
=
2
#COLD-#WARM
=
1
Nominal voltage U
N
= 6600 V
Nominal current I
Mot.nom
= 126 A
Starting current I
Start
= 624 A
Starting time at I
START
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
CT transformation ratio 200 A/1 A
I
Start
I
Mot.nom
⁄
624 A
126 A
---------------
4.95 4.9
≈
= =