Tau
3840
1920
960
640
480
320
16080
[s]
Figure 184: Trip curves at prior load 1 x FLC and p=50 %. Overload factor = 1.05.
4.1.11.5 Application
MPTTR is intended to limit the motor thermal level to predetermined values
during the abnormal motor operating conditions. This prevents a premature motor
insulation failure.
The abnormal conditions result in overheating and include overload, stalling, failure
to start, high ambient temperature, restricted motor ventilation, reduced speed
operation, frequent starting or jogging, high or low line voltage or frequency,
mechanical failure of the driven load, improper installation and unbalanced
1MRS757644 H
Protection functions
620 series
Technical Manual
369
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