IEC 60644 pdf download – Specification for high-voltage fuse-links for motor circuit applications
1 Scope
This standard applies primarily to fuse-links used with motors started direct-on-line onalternating current systems of 50 Hz and 60 Hz.
NOTE When motors are used with assisted starting this specification can also be applied but particular attentionshould be paid to the selection of the rated current of the fuse-link (see 8.1) and the manufacturer of the fuse-linkshould preferably be consulted.
Fuse-links according to this specification are intended to withstand normal service conditionsand motor starting pulses.They should comply with the requirements of lEC 60282-1.
The purpose of this standard is to standardize time-current characteristics, to formulate pulsewithstand requirements regarding testing and to give guidance regarding the selection of fuse-links intended to be used with motors.
2Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies.For undated references, the latest editionof the referenced document (including any amendments) applies.
lEC 60282-1:2005,High-voltage fuses – Part 1: Current-limiting fuses
3Fuse-link time-current characteristics
Compared to fuses typically used for distribution system protection， fuses for motor circuitprotection should have:
relatively high melting current (slow operation) in the 10 s region of the pre-arcing time-current characteristic to give maximum withstand against motor starting current;
relatively low melting current (fast operation) in the region below 0,1 s to give maximumshort-circuit protection to associated switching devices， cables and motors and theirterminal boxes.
Therefore pre-arcing time-current characteristics of fuse-links for motor circuit applicationsshall be within the following limits:
The term (1n/10o)0.25 is introduced to take account of the fact that the pre-arcing time-currentcharacteristics for a range of fuse-links diverge as they approach the short-time region.
4K factor
Factor which defines an overload characteristic to which the fuse-link may be repeatedlysubjected under specified motor starting conditions, and other specified motor-operatingoverloads, without deterioration.
For the purpose of this specification, the value of K is chosen at 10 s.Unless otherwise statedby the fuse-link manufacturer, it is valid from 5 s to 60 s, for a frequency of starts up to six perhour and for not more than two consecutive starts. For conditions different from thosespecified above，for example where service conditions involve inching, plugging or morefrequent starts, the manufacturer should be consulted.
The overload characteristic is obtained by multiplying the current on the pre-arcingcharacteristic by K (less than unity).
5 Withstand requirements
The performance of a fuse-link for motor circuit applications is in general determined by thefollowing criteria:
to withstand without deterioration starting pulses in rapid succession due for example toabnormal conditions,such as those occurring during commissioning of the equipment;
– to withstand without deterioration a large number of motor starts in normal service
conditions.
This standard therefore specifies two sequences of tests representative of these conditions:100 cycles corresponding to abnormal service conditions; 2 000 cycles corresponding tonormal service conditions. lt is expected that a fuse-link which passes these tests will have agood behaviour during a satisfactory life duration.
6 Withstand tests
6.1General
The withstand tests are type tests. Both test sequences shall be carried out on the same fuse-link.
The fuse-link shall be tested under the same test conditions as in 6.5.1.2 of lEC 60282-1.The values of test currents shall be K I 5,for pulses simulating the motor starting pulses andK 1 5,0/6 for periods simulating the normal motor running，1 4o being the pre-arcing current at10 s.The tolerance on both values shall be +18 %.
The duration of individual pulses shall be 10 s. The tolerance on the 10 s periods, both pulsesand off periods, shall be +0,5 s.
Tests shall be made at any convenient voltage and at a frequency from 48 Hz to 62 Hz.
IEC 60644 pdf download – Specification for high-voltage fuse-links for motor circuit applications
