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Required Charac-
The user communicates to the device the characteristic motor values supplied by the
teristic Values
manufacturer, which are necessary for calculation of the rotor temperature. These
values include the startup current Istart, the nominal motor current IMot.nom, the
maximum admissible startup time T START MAX (address 6603), the number of ad-
missible restart attempts under cold (n
The starting current is entered at address IStart/IMOTnom, expressed as a multiple
of the nominal motor current (6602). For a correct interpretation of this parameter, it
is important that in Power System Data 2 the nominal motor current (address 1102 is
correctly set. The number of warm starts allowed is entered at address 6606
(MAX.WARM STARTS) and the difference (6607) between the number of allowable
cold and warm starts is entered at address #COLD-#WARM.
For motors without separate ventilation, the reduced cooling at motor standstill can be
accounted for by entering 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 constants are the same at operating conditions (I > BkrClosed
I MIN).
Setting Example:
Example: Motor with the following data:
Rated voltage
Rated current
Startup current
Startup Duration for I
Allowable Starts with Cold Motor n
Allowable Starts with Warm Motor n
Current Transformer
The ratio between startup current and motor nominal current is:
The following settings are made:
IStart/IMOTnom
T START MAX
MAX.WARM STARTS
#COLD-#WARM
7UM61 Manual
C53000-G1176-C127-3
2.25 Restart Inhibit for Motors (ANSI 66, 49Rotor)
) and (n
cold
U
= 6600 V
N
I
= 126 A
Mot.nom
I
= 624 A
Start
T
= 8.5 s
STARTUP
START max
= 3
cold
= 2
warm
200 A / 1 A
= 4.9
= 8.5 sec
= 2
= 1
) conditions.
warm
153
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