GSS
3.3 Rated Breaking Capacity I 1 at U rat The rated breaking capacity characterizes the maximum current I 1 that the fuse-link can properly switch off at the rated voltage. In certain applications it may be necessary to reduce the expected short-circuit current by means of additional impedances in the electrical circuit.
I 1 I p
3.4 Voltage Drop The voltage drop is determined with the fuse-link in operation at its rated current and at an ambient temperature of 23°C. 3.5 Pre-arcing integral S The pre-arcing integral is calculated by integrating the square of the current over the pre-arcing time. The value indicates the electrical load that leads to the melting of the fuse-element. The value for the pre-arcing integral is determined at a test current of 10 I rat given and is as a typical value. 3.6 Operating integral A The operating integral is calculated by integrating the square of the current over the total operating time of the fuse link. The value is a measure of the load on the downstream components during breaking operation of the fuse link in the event of a short circuit. 3.7 Power dissipation P V The Power dissipation of a fuse link is calculated by multiplying the conventional nonfusing current I nf by the voltage drop If the maximum expected short circuit current (prospective current Ip) is not greater than 35 A or max. 10 I rat , then a miniature fuse link with an unfilled glass tube is used. This fuse-link has the advantage of a relatively low voltage drop. 4.2 The reinforced glass tube Miniature fuse-links with reinforced unfilled glass tubes can switch off prospective currents of up to 150 A at the rated voltage. 4.3 The filled glass tube Prospective currents of up to 1 000 A can be switched off at the rated voltage by a combination of quartz sand filling as extinguishing filler and reinforcement of the glass tube. 4.4 The filled ceramic tube A further increase in the rated breaking capacity up to a prospective current of several kA is achieved by the use of ceramic tubes filled with quartz sand. 4.5 The terminal caps A copper alloy is usually used as working material for the terminal caps. The caps are plated by means of a special surface treatment to provide better electrical and thermal contact, as well as for protection against corrosion. 5 Standards Besides several specific national standards, the principal standard applied worldwide is IEC 60127. It is divided into confirmation as well as one user’s manual. The German-language equivalent of this International Standard is VDE 0820. In the North American countries, the reference standard for miniature fuses is UL 248. Special care is required as in converting the rated currents of IEC 60127 into those according to UL 248 (see figure 1). one general part, parts dealing with the individual fuse designs, one part for fuse holders, one specification for quality 4 Structure of miniature Fuse-Links 4.1 The glass tube determined at this load after an hour.
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