IEC 60947-6-2:2020 pdf free download – Low-voltage switchgear and controlgear
5.4.2 Assignment of utilization categories based on the results of tests
a) A CPs which has been tested for one utilization category or at any combination of
parameters (such as highest operational voltage and current,etc.) can be assigned otherutilization categories without additional testing provided that the values of test current,voltages,power-factors or time-constants,number of operating cycles，the ON-times andOFF-times given in Table 9 and Table 10 and the test circuit for the assigned utilizationcategories are not more severe than those at which the equipment has been tested andtemperature-rise has been verified at a current not less than the highest assigned ratedoperational current in continuous duty.
For example, when tested for utilization category AC-4, a CPs may be assigned utilizationcategory AC-3 provided that I for AC-3 is not higher than 1,2 times I. for AC-4 at the samerated operational voltage.
b) DC-3 or DC-5 CPS is assumed to be capable of opening and closing loads other than those
on which they have been tested provided that:
– the voltage and current do not exceed the specified values of Ue and le;
5.4.3 Application of utilization categories for motor control dutyTypical service conditions are:
– rotation in one direction, the motor being switched off while running under normal service
conditions (utilization categories AC-2,AC-3 and AC-3e);
– rotation in two directions, but running of the motor in the second direction being started onlyafter the CPS has been switched off and the motor completely stopped(utilization categoriesAC-2,AC-3 and AC-3e);
– rotation in one direction，or in two directions as in the previous paragraph, but with thepossibility of infrequent inching. For this service condition, a direct-on-line CPs is generallyused (utilization category AC-3 and AC-3e);
– rotation in one direction with frequent inching (jogging); a direct-on-line CPS is generallyused (utilization category AC-4);
– rotation in one or two directions but with the possibility of infrequent plugging in order tostop the motor, the plugging being associated with rotor resistor braking if this is provided.ln this case a CPs may be used in the stator circuit (utilization category AC-2);
– rotation in two directions but with the possibility of reversing the supply connections to themotor while it is running in the first direction(plugging), in order to obtain its rotation in theother direction while switching off the motor running under normal service conditions.Adirect-on-line reversing cPs with plugging capability is generally used for this servicecondition (utilization category AC-4).
Unless otherwise stated,CPS’s used as starters are designed on the basis of the startingcharacteristics of the motors compatible with the making capacities of Table 9. When thestarting current of a motor exceeds these values,a CPs having a suitably higher ratedoperational current should be used.
Time-delay relay or release:
– definite time-delay: the time-delay of such relays or releases is independent of the over-current.The tripping time setting shall be stated as the duration in seconds of the openingtime of the CPs if the time-delay is not adjustable, or the minimum and maximum values ofthe opening time, if the time-delay is adjustable.
– inverse time-delay: the time-current characteristics shall be given in the form of curvessupplied by the manufacturer. These shall indicate how the opening time, starting from thecold state，varies with current within the range of operation of the relay or release.Themanufacturer shall indicate, by suitable means， the tolerances applicable to these curves.These curves shall be given for the minimum and maximum values of the current settingand, if the time setting for a given current setting is adjustable, it is recommended that theybe given in addition for each minimum and maximum values of the time setting.