1MAC050144-MB C
Section 4
Protection functions
615 series ANSI
307
Technical Manual
Internal FLC calculator
Full load current (FLC) of the motor is defined by the manufacturer at an ambient
temperature of 40°C. Special considerations are required with an application where the
ambient temperature of a motor exceeds or remains below 40°C. A motor operating at a
higher temperature, even if at or below rated load, can subject the motor windings to
excessive temperature similar to that resulting from overload operation at normal ambient
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, it appears that the motor is loaded beyond its rating. For calculating
thermal level it is better that the FLC values are scaled for different temperatures. The
scaled currents are known as internal FLC. An internal FLC is calculated based on the
ambient temperature shown in the table. The
Env temperature mode
setting decides
whether the thermal level calculations are based on FLC or internal FLC.
When the value of the
Env temperature mode
setting is set to the “FLC Only” mode, no
internal FLC is calculated. Instead, the FLC given in the data sheet of the manufacturer is
used. When the value of the
Env temperature mode
setting is set to “Set Amb Temp” mode,
internal FLC is calculated based on the ambient temperature taken as input through the
Env
temperature Set
setting.
Table 306: Modification of internal FLC
The ambient temperature is used for calculating thermal level and it is available through
the monitored data view from the
TEMP_AMB
output. The activation of the
BLOCK
input
does not affect the
TEMP_AMB
output.
When the Env temperature mode setting is on "Use input" mode, the internal FLC is
calculated from temperature data available through resistance temperature detectors
(RTDs) using the AMB_TEMP input.
The Env temperature Set setting is used,
• If the ambient temperature measurement value is not connected to the AMB_TEMP
input in ACT.
• When the ambient temperature measurement connected to MPTTR is set to "Not in
use" in the RTD function.
• In case of any errors or malfunctioning in the RTD output.
Thermal level calculator
The module calculates the thermal load considering the TRMS and negative sequence
currents. The heating up of the motor is determined by the square value of the load current.
Ambient Temperature T
amb
Internal FLC
<20°C
FLC x 1.09
20 to <40°C
FLC x (1.18 - T
amb
x 0.09/20)
40°C
FLC
>40 to 65°C
FLC x (1-[(T
amb
-40)/100])
>65°C
FLC x 0.75
Содержание 615 Series ANSI
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Страница 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
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Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
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