UL 248-13:2005 pdf download – Low-Voltage Fuses- Part 13: Semiconductor Fuses.
1 General
NOTE-
This Part is intended to be read together with the Standard for Low-Voltage Fuses – Part 1: General Requirements, hereatter
referred to as Part 1. The numbering of the Clauses in this Part correspond to like numbered Clauses in Part 1. The requirements
of Part 1 apply unless mooified by this Part. For Clauses not shown below, reter to the Standard for Low-Voltage Fuses – Part 1:
General Requirements, NMX-J-009/248/13-2000-ANCE◆CANCSA C22.2 No.248.1◆UL 248-1.
1.1 Scope
This Part applies to semiconductor fuses rated 2000 V ac or less. DC ratings are optional.
Note: The Canadian Electrical Code, Part 1, defines low vltage as any vltage from 31 to 750 V inclusive and high vltage as any
voltage above 750 V. The National Electrical Code, NFPA 70-1996 ，Section 710-2 defines high voltage as more than 600 V,
nominal.
2 Definitions
2.2 General Terms
2.2.15 Semiconductor fuse
A fuse, letter designation “R,” intended only for protection or isolation of semiconductor devices such as
SCR’s, diodes, and the like, and not branch-circuit protection.
2.2.15.1 “g” Fuse
A fuse capable of interrupting under specified conditions all currents which cause melting of the
fuse-element up to its interrupting rating.
2.2.15.2 “a” Fuse
A fuse capable of interrupting, under specified conditions, all currents between the lowest current specified
by the manufacturer and its interrupting rating.
4 Clasification
Semiconductor fuses are non-renewable. They shall provide short-circuit protection and may provide
overload protection.
gR – Full-range, overload and short- circuit protection.
aR – Partial-range, short-circuit protection.
5 Characteristics
5.2 Voltage rating
For AC, the rating shall be 2000 V ac or less.
The DC voltage rating may be dfferent from the AC rating.
5.5 Interrupting rating
For AC, the preferred ratings are 25,000, 50.000, 100.000, or 200,000 A.
For DC, the preterred ratings are 20,000, 50,000, 100,000, 150,000, or 200,000 A.
5.6 Peak let- through current and clearing 1P4 characteristics
Maximum values of peak let-through current and clearing Pt are provided by the manufacturer. See
Clause 8.5.3.
6 Marking
6.1 Marking of fuses
In addition to the marking requirements in Part 1: A semiconductor fuse shall be marked with:
e) the fuse class or classification (See Clause 6.2):
gR (Fll-range); or
aR (Partial-range); and
g) the marking “Current Limiting” may be applied if the fuse complies with the threshold ratio
test.
8.3 Verification of overload operation
For gR fuses, the overload operation point and maximum opening time shall be specified by the
manufacturer and shall be selected from the fllowing values:
135, 150, 160, 175, 200, or 250 percent of rating.
For fuses rated less than 600 A, two samples are to be tested. For fuses rated 600 A and greater, one
sample is to be tested.
8.4 Verification of operation at rated voltage
AC- Part 1, Table 5
Test 1 – High current specified by manufacturer
Test 2 – Maximum energy
Test 3 – Threshold ratio. Required for fuses marked “Current Limiting.” The maximum threshold
ratio shall be specified by the manufacturer.
Test 5 – Test to be conducted at a low current specified by manufacturer. Shall not be greater
than 800 percent of the fuse current rating, In. test current tolerance +0%一10%。
Notes:
a) peak let through current and clearing Pt recorded during Tests 1 and 2;
b) test circuit frequency shall be recorded; and
c) the maximum peak arc voltage is specilied by the manufacturer.
For DC- Part 1, Table 6
Test 1 – High current specified by manufacturer
Test 2 – Maximum energy
Test 5- Test to be conducted at a low current specified by manufacturer. Shall not be greater
than 800 percent of rating, In test current tolerance +0%一10%。