UL-248-1:2011 pdf free download – STANDARD FOR SAFETY Low-Voltage Fuses – Part 1: General Requirements.
8.2.4 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 characteristics, 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.
8.3.3.1 Overload test
The overload tests are conducted on a preset circuit or the current is to be adjusted to the required test current, within 3 s, at a uniform rate.
8.3.3.2 Time-delay test
The time-delay test is to be conducted on a preset circuit adjusted to the required test current using a copper bar equivalent to the fuse contact dimensions in the circuit. The copper bar is then to be replaced with the test fuse, the circuit turned on, and readjusted to the required test current, within 3 s, at a uniform rate.
8.4.2.4 Measuring instrumentation
The measurement of test parameters — current, voltage, and time for example — shall be made in accordance with Annex B, or with electronic systems that have been shown to be equivalent to these methods.
8.4.3 Test method
To verify performance, one fuse at a time shall be tested in accordance with Table 5 for AC and Table 6 for DC.
8.4.3.1 Tests 1, 2, 3, 4a, 4b
If the available current for any test is greater than the interrupting rating, then the test is waived. For AC tests 1, 4a, 4b the closing angle of the test circuit shall be between 00 and 900 on the voltage wave.
For AC test 3, the closing angle shall be between 80° and 90°, with reference to the voltage wave.
8.4.3.2 Tests 5a, 5b, 5c
The fuse may be pre-heated by means of a reduced voltage circuit. This current shall be within ± 20 percent of the required test current. The switchover to the test circuit shall be before the arc is initiated. (The switching time should not exceed 1 .0 s).
At least one full cycle (or at least 17 ms) of current at rated voltage shall flow before arcing starts.
The time required for the fuse to clear and the duration of arcing are not specified.
8.4.4 Acceptability of test results.