Thermal Overload Protection For Motors Mpttr (Ansi 49M) - ABB RELION REX640 Technical Manual

Protection functions
Characteristic
Start time
Reset time
Reset ratio
Retardation time
Operate time accuracy in definite time mode mode ±1.0% of the set value or ±20 ms
4.1.10 Thermal overload protection for motors MPTTR (ANSI
49M)
4.1.10.1 Identification
Function description
Thermal overload protection for
motors
4.1.10.2 Function block
Figure 237: Function block
4.1.10.3 Functionality
The thermal overload protection for motors function MPTTR protects the electric
motors from overheating. MPTTR 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. MPTTR 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.
4.1.10.4 Analog channel configuration
MPTTR has one analog group input which must be properly configured.
Table 475: Analog inputs
Input
I3P
410
Value
Typically <55 ms
<40 ms
Typically 1.04
<35 ms
IEC 61850 IEC 60617
identification identification
MPTTR 3Ith>M
Description
Three-phase currents
1MRS759142 F
ANSI/IEEE C37.2
device number
49M
REX640
Technical Manual