IEC 60644 pdf download Specification for high-voltage fuse-links for motor circuit applications
This standard applies primarily to fuse-links used with motors started direct-on-line on alternating current systems of 50 Hz and 60 Hz. NOTE When motors are used with assisted starting this specification can also be applied but particular attention should be paid to the selection of the rated current of the fuse-link (see 8.1 ) and the manufacturer of the fuse-link should preferably be consulted. Fuse-links according to this specification are intended to withstand normal service conditions and motor starting pulses. They should comply with the requirements of IEC 60282-1 .
The purpose of this standard is to standardize time-current characteristics, to formulate pulse withstand requirements regarding testing and to give guidance regarding the selection of fuse- links intended to be used with motors.
2 Normative 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 edition of the referenced document (including any amendments) applies.
IEC 60282-1 :2005, High-voltage fuses
– Part 1: Current-limiting fuses 3 Fuse-link time-current characteristics Compared to fuses typically used for distribution system protection, fuses for motor circuit protection should have:
– relatively high melting current (slow operation) in the 1 0 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 maximum short-circuit protection to associated switching devices, cables and motors and their terminal boxes. Therefore pre-arcing time-current characteristics of fuse-links for motor circuit applications shall be within the following limits:
I n is the numerical value of the current rating, expressed in amperes, of the fuse-link;
The term ( ) 25 , 0 100 n I is introduced to take account of the fact that the pre-arcing time-current characteristics for a range of fuse-links diverge as they approach the short-time region.
4 K factor
Factor which defines an overload characteristic to which the fuse-link may be repeatedly subjected under specified motor starting conditions, and other specified motor-operating overloads, without deterioration. For the purpose of this specification, the value of K is chosen at 1 0 s.
Unless otherwise stated by the fuse-link manufacturer, it is valid from 5 s to 60 s, for a frequency of starts up to six per hour and for not more than two consecutive starts. For conditions different from those specified above, for example where service conditions involve inching, plugging or more frequent starts, the manufacturer should be consulted.