Function Block; Functionality; Operation Principle - ABB RELION 620 Series Technical Manual

1MAC504801-IB E
4.5.3.2
4.5.3.3
4.5.3.4
620 series ANSI
Technical Manual

Function block

GUID-5552A9D8-ADEF-4153-AB1A-0C97F97D15EB V3 EN
Figure 177: Function block

Functionality

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. The
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 the motor thermal overload protection function can be described using a
module diagram. All the modules in the diagram are explained in the next sections.
Section 4
Protection functions
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