AS NZS IEC 60947.4.2:2015 pdf free download.Low-voltage switchgear and controlgear Part 4.2: Contactors and motorstarters- AC semiconductor motor controllers and starters.
5.3.2 Currents
A controller or starter is defined by the following currents:
5.3.2.1 Conventional free air thermal current (Ith) Subclause 4.3.2.1 of IEC 60947-1:2007 applies.
5.3.2.2 Conventional enclosed thermal current (‘the) Subclause 4.3.2.2 of IEC 60947-1:2007 applies.
5.3.2.3 Rated operational current (le)
The rated operational current, ‘e of controllers and starters is the normal operating current when the device is in the FULL-ON state, and takes into account the rated operational voltage (see 5.3.1.1), the rated frequency (see 5.3.3), the rated duty (see 5.3.4), the utilization category (see 5.4), the overload characteristics (see 5.3.5), and the type of protective enclosure, if any.
5.3.2.4 Rated uninterrupted current (Ia)
Subclause 4.3.2.4:2007 of IEC 60947-1:2007 applies.
5.3.3 Rated frequency
Subclause 4.3.3:2007 of IEC 60947-1:2007 applies.
5.3.4 Rated duty
The rated duties considered as normal are as follows:
5.3.4.1 8 h duty
A duty in which the controller or starter remains in the FULL-ON state while carrying a steady current long enough for the equipment to reach thermal equilibrium, but not for more than 8 h, without interruption.
5.3.4.2 Uninterrupted duty
A duty in which the controller or starter remains in the FULL-ON state while carrying a steady current without interruption for periods of more than 8 h (weeks, months, or even years).
5.3.4.3 Intermittent periodic duty or intermittent duty
Subclause 4.3.4.3:2007 of IEC 60947-1:2007 applies, except that the first paragraph is changed as follows:
“A duty with on-load periods in which the controller or starter remains in the FULL-ON state, having a definite relation to off-load periods, both periods being too short to allow the equipment to reach thermal equilibrium.”
5.3.4.4 Temporary duty
Duty in which the controller or starter remains in the FULL-ON state for periods of time insufficient to allow the equipment to reach thermal equilibrium, the current-carrying periods being separated by off-load periods of sufficient duration to restore equality of temperature with the cooling medium. Standard values of temporary duty are as follows:30s,1min,3min,10min,30min,60minand90min.AS NZS IEC 60947.4.2 pdf download.