ABB RELION REX640 Technical Manual page 427

1MRS759142 F
Table 486: Time constant and the respective phase current values
Time constant in
use
tStart
tNormal
tStop
Setting
curves θA and θB.
The thermal level of the rotor at power up of the protection relay is defined by the
setting
The temperature calculation is initiated from the value defined in the
Val setting. This is done if the protection relay is powered up or the function is
turned off and back on or reset through the Clear menu.
Calculated thermal level TEMP_RL is available in monitored data view.
Thermal levels at the beginning and the end of the latest startup are
available through the monitored data view at THERMLEV_ST and THERMLEV_END
respectively.
Internal FLC calculator
Full load current (FLC) of the motor is defined by the manufacturer at an
ambient temperature of 40°C. The FLC of the motor is set by
setting. Special considerations are required with an application where the ambient
temperature of a motor exceeds or remains below 40°C. A motor operating in a
higher ambient temperature, even at or below rated load, can subject the motor
windings to excessive temperature. The motor rating has to be appropriately
reduced for operation in such high ambient temperatures. Similarly, when the
ambient temperature is considerably lower than the nominal 40°C, the motor can
be slightly overloaded. For calculating thermal level, it is better that the FLC values
are scaled for different temperatures. The scaled currents are known as internal FLC
(I
IFLC
The
are based on FLC or
When the value of the
no I
used. When the value of the
mode, the
through the Env temperature Set setting. When the
is on "Use input" mode, the
through resistance temperature detectors (RTDs) using the AMB_TEMP input.
Table 487: Temperature dependency of I
Ambient Temperature (T
<20°C
20 to <40°C
40°C
>40 to 65°C
>65°C
REX640
Technical Manual
Phase current
Any current is over 2.5 ∙
Any current is over 0.12 ∙
All currents are below 0.12 ∙
Weighting factor p determines the ratio of the thermal increase of the two
Initial thermal Val .
I
). An is calculated based on the ambient temperature shown in the table.
IFLC
Env temperature mode setting defines whether the thermal level calculations
I
.
IFLC
Env temperature mode setting is set to the "FLC Only" mode,
is calculated. Instead, the FLC given in the data sheet of the manufacturer is
IFLC
I
is calculated based on the ambient temperature taken as an input
IFLC
amb
I
IFLC
I
and all currents are below 2.5 ∙
IFLC
I
IFLC
Env temperature mode setting is set to "Set Amb Temp"
I is calculated from temperature data available
IFLC
IFLC
) I
IFLC
FLC x 1.09
FLC x (1.18 - T
FLC
FLC x (1 –[(T
FLC x 0.75
Protection functions
I
IFLC
Initial thermal
Current reference
Env temperature mode setting
x 0.09/20)
amb
-40)/100])
amb
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