Function Block; Functionality; Operation Principle - ABB 615 series Technical Manual

Section 4
Protection functions
4.1.9.2
4.1.9.3
4.1.9.4
298

Function block

GUID-5552A9D8-ADEF-4153-AB1A-0C97F97D15EB V3 EN
Figure 141: Function block

Functionality

The thermal overload protection for motors function 49M protects the electric motors
from overheating. 49M models the thermal behavior of motor on the basis of the measured
load current and disconnects the motor when the thermal content reaches 100 percent.
Thermal overload conditions are the most often encountered abnormal conditions in
industrial motor applications. The thermal overload conditions are typically the result of
an abnormal rise in the motor running current, which produces an increase in the thermal
dissipation of the motor and temperature or reduces cooling. 49M prevents an electric
motor from drawing excessive current and overheating, which causes the premature
insulation failures of the windings and, in worst cases, burning out of the motors.

Operation principle

The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of 49M can be described using a module diagram. All the modules in the
diagram are explained in the next sections.
The function uses ambient temperature which can be measured locally or remotely. Local
measurement is done by the protection relay. Remote measurement uses analog GOOSE
to connect AMB_TEMP input.
If the quality of remotely measured temperature is invalid or
communication channel fails the function uses ambient temperature set in
Env temperature Set.
1MAC059074-MB A
615 series ANSI
Technical Manual