Configuration
6.2 Overload relays in motor feeders
SIRIUS Innovations - SIRIUS 3RU2 thermal overload relays / SIRIUS 3RB3 solid-state overload relays
52 Manual, 09/2014, A5E03656507420A/RS-AA/002
Normal and heavy-duty starting
Normal starting
Selecting the right overload relay means considering the start time as well as the rated motor
current. The start time refers to the time required by the motor between switching on and
reaching its rated speed.
Table 6- 4 Normal starting
Normal starting < 10 s
Heavy-duty starting > 10 s
Overload relays with corresponding tripping classes are required to protect heavy-duty-
starting motors (for the acceleration of large centrifuges, for example). In the case of heavy-
duty starting, the cables and contactors also have to be dimensioned specifically on account
of the increasing thermal load.
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