UL 248-1:2011 pdf download – Low-Voltage Fuses – Part 1: General Requirements
UL 248-1:2011 pdf download – Low-Voltage Fuses – Part 1: General Requirements.
8.2.3 Test method
The current carrying capacity test, which confirms the conventional non-fusing current, I. is conducted as part of the temperature rise test.
Measurement of temperatures shall be by thermocouples. The thermocouples shall be secured by Fuller’s earth and waterglass. welding, soldering, o other method that provides thermal contact.
The thermocouples shall consist of iron and constantan or chromel and alumel wires not larger than No. 24 AWG (021 mm2).
An alternative method of temperature measurement may be used if upon investigation it is shown that tile alternative method provides equivalent results.
184.108.40.206 Fuses rated 600 A or less
Fuses rated 600 A or less shalt carry 1.0 In until temperature stabilization occurs.
Stabilization shall be considered to have occurred when no individual temperature rise reading of 4 consecutive readings taken at 5 mm intervals exceeds the average reading of these 4 readings by more than 2°C and no indication of increasing temperature rise is observed. This average temperature rise reading shall be deemed to be the temperature rise of the fuse.
Thermocouples shall be placed against the center of the top or upper surface of the fuse — midway between the caps or ferrules on the body and on each ferrule or blade at the top center of the fuse clip.
220.127.116.11 Fuses rated 601 — 6000 A
Fuses rated more than 600 A shall carry 1.1 In until temperature stabilization occurs.
Stabilization shall be considered to have occurred when no individual temperature rise reading of 4 consecutive readings taken at tO mm intervals exceeds the average reading of these 4 readings by more than 2°C and no indication of increasing temperature rise is observed. This average temperature rise reading shall be deemed to be the temperature rise of the fuse.
The test equipment shall be calibrated, with a shorting bar substituted for the fuse to be tested. to produce a temperature rise on the shorting bar within the limits specified in Table 3.
The shorting bar shall be the same length as the fuse for which it is substituted. The cross-sectional dimensions of the shorting bar shall be the same as those of the bus bar. The shorting bar shall be of copper, shall be silver-plated at the terminal connections, shall have holes to permit mounting to the bus bar, and shall be one-piece or laminated without space between the laminations.
During calibration, a thermocouple shall be located at the top center of the shorting bar.
During the temperature test, a thermocouple shall be secured at the top center of each fuse contact, approximately 6.4 mm (1/4 in) from the end of the fuse body.
8.2A Acceptability of test results
No external soldered connections shall melt. The fuse body or label may discolor but shall not char nor rupture in any manner and shall be readily identifiable for replacement purposes.
The temperature rise limits specified in the relevant subsequent Parts shall not be exceeded.
Fuses shall not open during this test.
8.3 Verification of overload operation
8.3.1 Arrangement of fuse
The arrangement of the fuse shall be as specified in arrangement of the fuse, Clause 8.2.1.
8.3.2 Test circuit
The test circuit shall be as specified in Test circuit charactenstics, Clause 8.2.2.
8.3.3 Test method
Fuses are to be tested singly or a number of fuses not exceeding three may be tested in series. If a manufacturer so elects, fuses that performed acceptably in temperature rise or current carrying tests may be used for overload operation tests, The temperature of such fuses is not to be higher than that of the ambient air when the overload operation test is started.
18.104.22.168 Overload test
The overload tests are conducted on a peset circuit or the current is to be adjusted to the required test current, within 3 s, at a uniform rate.
22.214.171.124 Time-delay test.