BS EN 60269-1-2007 pdf download.Low-voltage fuses Part 1 : General requirements.
5.7.2 Rated breaking capacity
The rated breaking capacity of a fuse-link is given by the manufacturer corresponding to the
rated voltage. Values of minimum rated breaking capacity are given in subsequent parts.
5.8 Cut-off current and 12t characteristics
The value for cut-off and 12t characteristics shall take into account manufacturing tolerances and shall refer to the service conditions as specified in subsequent parts, for example, the values of voltage, frequency and power factor.
5.8.1 Cut-off current characteristics
The cut-off current characteristics shall represent the maximum instantaneous values of current likely to be experienced in service (see 8.6.1 and Annex C).
Where the cut-off current characteristics are required, and unless specified In subsequent parts, they should be given by the manufacturer according to the example shown in Figure 4, in a double logarithmic presentation with the prospective current as abscissa.
5.8.2 12t characteristics
The pre-arcing 121 characteristics for pre-arcing times of less than 0,1 s down to a time corresponding to the rated breaking capacity shall be given by the manufacturer. They shall represent the lowest values likely to be experienced in service as a function of the prospective current.
The operating 121 characteristics with specified voltages as parameters shall be given by the manufacturer for pre-arcing times less than 0,1 s. They shall represent the highest values likely to be experienced in service as a function of the prospective current.
When presented graphically, the 121 characteristics shall be given with prospective current as abscissa and 121 values as ordinate. Logarithmic scales shall be used on both coordinate axes. (For the use of the logarithmic scales, see 5.6.1.)
6 Markings
The marking shall be durable and easily legible. Compliance is checked by inspection and by the following test.
The marking is rubbed by hand for 5 s with a piece of cloth soaked with water and again for 5 s with a piece of cloth soaked with petroleum spirit.
— name of the manufacturer or a trade mark by which he may be readily identified;
— manufacturer’s identification reference, enabling all the characteristics listed in 5.1.2 to be found;
— rated voltage;
— rated current (for “gM type see 5.7.1):
— breaking range and utilization category (letter code), where applicable (see 5.7.1);
— kind of current and, if applicable, rated frequency (see 5.4).
NOTE Fuse-links should be marked separately for ac, and d.c. if the fuse-link is provided for ac. and d.c.
For small fuse-links, where it is impracticable to include all the specified information on the fuse-link, the trade mark, list reference of the manufacturer, rated voltage and the rated current shall be marked.
6.3 Marking symbols
For the kind of current and frequency, use symbols in accordance with IEC 60417.
NOTE The marking for rated current and rated voltage may. for instance, be as follows. 10 A 500 V or 101500 or
500
7 Standard conditions for construction
7.1 Mechanical design
7.1.1 Replacement of fuse-links
A fuse-link shall have adequate mechanical strength and its contacts shall be securely fixed. It shall be possible to replace the fuse-links easily and safety.
7.1.2 Connections, including terminals
The fixed connections shall be such that the necessary contact force is maintained under the conditions of service and operation.
No contact force on connections shall be transmitted through insulating material other than ceramic or other material with characteristics not less suitable, unless there is sufficient resilience in the metallic parts to compensate for any possible shrinkage or other deformation of the insulating material. Tests are specified in subsequent parts, where necessary.
7.1.3 Fuse-contacts
Fuse-contacts shall be such that the necessary contact force is maintained under the
conditions of service and operation, in particular under the conditions corresponding to 7.5.
Contact shall be such that the electromagnetic forces occurring during operation under conditions in accordance with 7.5 shall not impair the electrical connections between
a) the fuse-base and the fuse-carrier;
b) the fuse-carrier and the fuse-link;
C) the fuse-link and the fuse-base, or, if applicable, any other support.
In addition, fuse contacts shall be so constructed and of such material that, when the fuse is properly installed and service conditions are normal, adequate contact is maintained
a) after repeated engagement and disengagement;
b) after being left undisturbed In service for a long period (see 8.10).
Fuse-contacts of copper alloy shall be free from season cracking.
These requirements are verified by the tests according to 8.10, 8.11.2.1 and in Clause 8 of subsequent parts.
7.1.4 Construction of a gauge-piece
A gauge-piece, if any, shall be so designed that it withstands normal stresses occurring during use.
7.1.5 Mechanical strength of the fuse-link
A fuse-link shall have adequate mechanical strength and its contacts shall be securely fixed.
7.2 Insulating properties and suitability for isolation
The fuses shall be such that they do not lose their insulating properties at the voltages to which they are subjected in normal service. When the equipment is in its normal open position, the fuse-link remaining inside the fuse-carrier, or when the fuse-link, and, where applicable, the fuse-carrier is removed, the fuse shall be suitable for isolation. The applicable overvoltage category is specified in subsequent parts.
The fuse shall be deemed to satisfy these conditions if it passes the tests for verification of insulating properties and suitability for isolation in accordance with 8.2.BS EN 60269-1-2007 pdf download.