Worldwide Circuit Protection Solutions
Bussmann®
This catalog is intended to present product data and provide technical information that will
help the end user with design application. Bussmann reserves the right, without notice,
to change design or construction of any products and to discontinue or limit distribution
of any products. Bussmann also reserves the right to change or update, without notice,
any technical information contained in this catalog. Once a product has been selected, it
should be tested by the user in all possible applications.
©2002 Cooper Bussmann
Printed in the U.S.A.
World’s leading supplier of fuses and fusible protection
systems, Bussmann continues its 88-year history of blazing new
trails of innovative technologies. Maker of the industry’s first
truly global product line, each item is backed by an efficient
worldwide network of distribution, customer service and
technical support. Bussmann products include the most
extensive circuit protection solutions approved for use in
a variety of major standards: UL, CSA, IEC. . . Not to
mention both European (DIN, British Standard) and
North American styled fuses for a wide range of
applications: industrial motor protection, power
conversion, medium voltage, power distribution,
telecommunications network equipment, electronics,
and automotive. Manufacturing operations in the U.S.,
Denmark, and the United Kingdom have earned ISO
9000 certification. Bussmann customers are assured
of only the utmost quality across every product line.
Knowledgeable. Responsive. Customer focused.
Bussmann continues to set the standard for circuit
protection solutions around the world.
1 Electrical – Power Fuses 1
2 Electronic – PC Board and Small Dimension Fuses 29
3 Fuseblocks and Holders 41
4 Disconnect Switches 99
5 High Speed Fuses 123
6 Medium Voltage Fuses and Fuse Links 157
7 Telecommunications Protection 175
8 British, European, & Canadian Standard Industrial Fuses 189
9 Fuse Accessories, Displays, Kits, Etc. 202
10 Fuse Technology 210
Glossary of Terms 231
Index 233
Bussmann®
i
Section Guide
Bussmann
Information Fax ~
636.527.1450
Page
Now you can get current information about Bussmann products at anytime,using BIF (Bussmann Information FAX) or visit us on the World Wide Web.
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©2002 Cooper Bussmann Printed in U.S.A.
Bussmann
Worldwide Web ~http://www.bussmann.com
General Data – Dimensions (Inches) Bussmann®
2
A
B
CLASS TT-Tron™ Fuses
JJN (300V) JJS (600V)
CLASS JLow-Peak® & Limitron® Fuses
LPJ & JKS (600V)
CLASS L Low-Peak® & Limitron® Fuses
KRP-C, KTU, & KLU (601 - 6000A) (600V)NOTE: KRP-CL (150A to 600A) fuses
have same dimensions as 601A to
800A case size. KTU (200A to 600A)
have same dimensions, except tube
3∑ lgth. ≈ 2∑ dia.; terminal 1fi/•∑ width
≈ 1⁄/¢∑ thick.
CLASS RK5 & RK1Fusetron®, Low-Peak® &
Limitron® Fuses (250V & 600V)FRN-R & FRS-R; LPN-RK & LPS-RK; KTN-R & KTS-RBasic dimensions are same as Class H (for-
merly NEC) ONE-TIME (NON & NOS) and
SUPERLAG Renewable RES & REN fuses.
NOTE: These fuses can be used to replace
existing Class H, RK1 and RK5 fuses relating
to dimensional compatibility.
250V 600V
Ampere A B A B
⁄Ω¡º-30 2∑ .56∑ 5∑ .81∑
35-60 3∑ .81∑ 5.5∑ 1.06∑
Fusetron & Limitron
250V 600V
Ampere A B A B
70-100 5.88∑ 1.06∑ 7.88∑ 1.34∑
110-200 7.13∑ 1.56∑ 9.63∑ 1.84∑
225-400 8.63∑ 2.06∑ 11.63∑ 2.59∑
450-600 10.38∑ 2.59∑ 13.38∑ 3.13∑
Low-Peak
250V 600V
Ampere A B A B
70-100 5.88∑ 1.16∑ 7.88∑ 1.16∑
110-200 7.13∑ 1.66∑ 9.63∑ 1.66∑
225-400 8.63∑ 2.38∑ 11.63∑ 2.38∑
450-600 10.38∑ 2.88∑ 13.38∑ 2.88∑
A
B
Bussmann®
General Data – Dimensions (Millimeters)
3
A
B
CLASS TT-Tron™ Fuses
JJN (300V) JJS (600V)
CLASS JLow-Peak® & Limitron® Fuses
LPJ & JKS (600V)
CLASS L Low-Peak® & Limitron® Fuses
KRP-C, KTU, & KLU (601 - 6000A) (600V)NOTE: KRP-CL (150A to 600A) fuses
have same dimensions as 601A to
800A case size. KTU (200A to 600A)
have same dimensions, except tube
76.2mm lgth. x 50.8mm dia.; terminal
41,3mm width x 31.8mm thick.
CLASS RK5 & RK1Fusetron®, Low-Peak® &
Limitron® Fuses (250V & 600V)FRN-R & FRS-R; LPN-RK & LPS-RK; KTN-R & KTS-RBasic dimensions are same as Class H (for-
merly NEC) ONE-TIME (NON & NOS) and
SUPERLAG Renewable RES & REN fuses.
NOTE: These fuses can be used to replace
existing Class H, RK1 and RK5 fuses relating
to dimensional compatibility.
250V 600V
Ampere A B A B
⁄Ω¡º-30 50.8 14.3 127.0 20.6
35-60 76.2 20.6 139.7 27.0
Fusetron & Limitron
250V 600V
Ampere A B A B
70-100 149.2 26.9 200.0 34.0
110-200 181.0 39.6 244.5 46.7
225-400 219.1 52.3 295.3 65.8
450-600 263.5 65.8 339.7 79.5
Low-Peak
250V 600V
Ampere A B A B
70-100 149.2 29.5 200.0 29.5
110-200 181.0 42.2 244.5 42.2
225-400 219.1 60.5 295.3 60.5
450-600 263.5 73.2 339.7 73.2
A
B
Bussmann®
17For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Electrical - Power Fuses
Data Sheet: 1006 (0-60) and 1007 (70-600)
Low-Peak®
Dual-Element, Time-Delay, Class J Fuses
LPJ_SPDual-Element,
Time-Delay –
10 seconds (minimum) at
500% rated current
Ampere Ratings:
1-600A
Voltage Rating:
600Vac (or less),
300Vdc (or less)
Current Limiting
Interrupting Rating:
ac – 300,000A RMS Sym. dc – 100,000A
Agency Information:
UL Listed - Special Purpose**, Guide JFHR, File E56412
CSA Certified (200,000 AIR) Class J per CSA-22.2 No. 248.8,
Class 1422-02, File 53787
Dimensions: See pages 2-3 for Class J dimensional data.
Catalog Numbers
LPJ-1SP LPJ-4⁄Ω™SP LPJ-25SP LPJ-125SP
LPJ-1⁄Ω¢SP LPJ-5SP LPJ-30SP LPJ-150SP
LPJ-1flꭧSP LPJ-5flꭧSP LPJ-35SP LPJ-175SP
LPJ-1°Ω¡ºSP LPJ-6SP LPJ-40SP LPJ-200SP
LPJ-2SP LPJ-7SP LPJ-45SP LPJ-225SP
LPJ-2⁄Ω¢SP LPJ-8SP LPJ-50SP LPJ-250SP
LPJ-2⁄Ω™SP LPJ-9SP LPJ-60SP LPJ-300SP
LPJ-2°Ω¡ºSP LPJ-10SP LPJ-70SP LPJ-350SP
LPJ-3SP LPJ-12SP LPJ-80SP LPJ-400SP
LPJ-3¤Ω¡ºSP LPJ-15SP LPJ-90SP LPJ-450SP
LPJ-3⁄Ω™SP LPJ-17⁄Ω™SP LPJ-100SP LPJ-500SP
LPJ-4SP LPJ-20SP LPJ-110SP LPJ-600SP
**Meets all performance requirements of UL Standard 248-8 for Class J fuses.Available with silver plated terminals. Add SP/ in front of part number.
Carton Quantity and Weight
Ampere Carton Weight*
Ratings Qty. Lbs. Kg.
0-30 10 1.09 0.49
35-60 10 1.78 0.81
70-100 5 1.69 0.77
110-200 5 4.21 1.91
225-400 1 1.67 0.76
450-600 1 2.80 0.27
*Weight per carton.
AMPERERATING1
A
3A
6A
300
100
10
1
.1
.01
TIM
E IN
SE
CO
ND
S
10A
15A
30A
60A
100A
400A
1,0
00
100
CURRENT IN AMPERES
600A
125A
250A
200A
80A
200
10
10,0
001
INS
TA
NTA
NE
OU
S P
EA
K L
ET-T
HR
U C
UR
RE
NT
IN
AM
PS 100,000
10,000
1,000
100
B
A
PROSPECTIVE SHORT-CIRCUIT CURRENTSYMMETRICAL RMS AMPS
10
0
1,0
00
10
,00
0
10
0,0
00
20
0,0
00
600A
400A
200A
100A
60A
30A
15A
RA
AM
PE
RE
TIN
G
LPJ Current Limitation Curves
30
0,0
00
Time-Current Classification Curves—Average Melt
Current Limitation Curves
CE logo denotes compliance with European Union Low Voltage Directive(50-1000Vac, 75-1500Vdc). Refer to Data Sheet: 8002 or contactBussmann Application Engineering at 636-527-1270 for more information.
Recommended fuseblocks/fuseholders for
Class J 600V fuses
• Open fuseblocks - see pages 53-55
• Finger-safe fuseholders for 30A & 60A-
see pages 57-58
• Modular fuseblocks - see page 67
Bussmann®
18 For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Electrical - Power Fuses
Data Sheet: 1026 (1-60A), 1027 (70-600A)
Limitron®
Quick Acting, Class J Fuses
JKSQuick Acting
Ampere Ratings: 1-600A
Voltage Rating: 600Vac (or less)
Current Limiting
Interrupting Rating: 200,000A RMS Sym.
Agency Information: Std. 248-8, Class J
UL Listed, Guide JDDZ, File E4273
CSA Certified, Class 1422-02, File 53787
Dimensions: See pages 2-3 for Class J dimensional data.
Catalog Numbers
JKS-1 JKS-15 JKS-70 JKS-225
JKS-2 JKS-20 JKS-80 JKS-250
JKS-3 JKS-25 JKS-90 JKS-300
JKS-4 JKS-30 JKS-100 JKS-350
JKS-5 JKS-35 JKS-110 JKS-400
JKS-6 JKS-40 JKS-125 JKS-450
JKS-8 JKS-45 JKS-150 JKS-500
JKS-10 JKS-50 JKS-175 JKS-600
JKS-12 JKS-60 JKS-200
Carton Quantity and Weight
Ampere Carton Weight*
Ratings Qty. Lbs. Kg.
1-30 10 0.95 0.43
35-60 10 1.175 0.53
70-100 5 0.28 0.13
110-200 1 0.86 0.39
225-400 1 1.78 0.81
450-600 1 3.07 1.39
*Weight per carton.
Fuse Reducers for J Dimension Fuses
Cat. Weight Cat. WeightClip Fuse No. Carton* Clip Fuse No. Carton*Size Size (Pair) (lbs) Size Size (Pair) (lbs)
60A 30A J63 0.38 400A 100A J41 4.90
100A 30A J13 1.73 400A 200A J42 2.75
100A 60A J16 1.85 600A 400A J64 3.55
200A 60A J26 2.55 600A 200A J62 3.55
200A 100A J21 1.36 — — — —
*Carton quantity—10 pair.
CE logo denotes compliance with European Union Low Voltage Directive(50-1000Vac, 75-1500Vdc). Refer to Data Sheet: 8002 or contactBussmann Application Engineering at 636-527-1270 for more information.
Recommended fuseblocks/fuseholders for
Class J 600V fuses
• Open fuseblocks - see pages 53-55
• Finger-safe fuseholders for 30A & 60A-
see pages 57-58
• Modular fuseblocks - see page 67
Bussmann®
54 For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Fuseblocks, Holders and Terminal Blocks
Class J Fuseblocks
Data Sheet: 1114
3.5"
1.75"
3"
.625"
.75"
C'Bore.34"
DIA.
.5"
7.5"
1"
4"
.56"
.75"
3.1"
.31"
6.125"
3.06"
2"
3"
.5"
.75"
C'Bore
.34"
DIA.
FIGURE 6.
101-200A
201-400A
6.125"
7.00"
8.31"
1.69"
.344" Dia. hole thru
.750 Dia. c'bore
3.15"
.750"
FIGURE 7.
9.00"
10.51"
7.50"
2.00"
.344" Dia. hole thru
.750 Dia. c'bore
4.00"
1.00"
6.00"
.50"
FIGURE 8. FIGURE 9.
.56"
8.875"
3.25"
1.75"
.75"
C'Bore
.34" Dia.
4"
2.375"
1.125"
1"
4.99"401-600A
FIGURE 10.
8.875"
11.00"
14.144"
.344" Dia.
hole thru
.750 Dia.
c'bore
2.88"
4.987"
1.00"
.50"
FIGURE 11.
Bussmann®
55For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Fuseblocks, Holders and Terminal Blocks
Data Sheet:1108
Class J Fuseblocks
ADAPTOR FOR 35mm SYMMETRICAL DIN-RAIL MOUNTING
2.78"(70.6mm)3.06"
(77.8mm)
3.13"(79.5mm)
JP Series For use with Class J Fuses(Bussmann LPJ,JKS).
Pyramid Style FuseblockAmpere Rating: 30AVoltage Rating: 600V
Withstand Rating: 200,000 RMS Sym. Amps
Agency Information:
UL Listed, U.L. 512, Guide IZLT, File E14853
CSA Certified, C22.2 No. 39, Class 4225-04, File 47235
Material: Thermoplastic
UL Flammability: UL 94V0
3.29"(83.6mm)
END STOPS - PREVENT BLOCK MOVEMENT WHEN CHANGING FUSES
DIN-RAIL MOUNTING SCREW 8" (203.2mm) APART
4.00" MAX.(101.6mm)
1.19"(30.2mm)
3.75" (±0.02)(95.3mm (±0.50)
1.88"(47.6mm)
2.38"(60.4mm)
Dimensional Data *All other dimensions (± 0.015∑)
(± 0.40mm)
CE logo denotes compliance with European Union Low Voltage Directive(50-1000 Vac, 75-1500 Vdc). Refer to Data Sheet: 8002 or contactBussmann Application Engineering at 314-527-1270 for more information.
Pyramid®
J Fuseblock; 30A, 600V; 3-Pole; Panel or 35mmDIN-Rail Mount; Clips with Reinforcing Springs
Mounting Catalog Numbers
Screws with BoxPressure Copper
Plate Aluminum Only
Panel JP60030-3PR JP60030-3CR JP60030-3COR(#10-14 CU ONLY) (#2-14 CU/AL) (#2-14 CU ONLY)
With JP60030-3PRA JP60030-3CRA JP60030-CORADIN-Rail (#10-14 CU ONLY) (#2-14 CU/AL) (#2-14 CU ONLY)Adapter*
*Adapter Only for DIN-Rail - Cat No. JPA-3.
Bussmann®
56 For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Fuseblocks, Holders and Terminal Blocks
Data Sheet: 1211
Semiconductor Fuseblocks
J70100 Ampere Rating: 100A
Voltage Rating: 700V
Agency Information:
UL Recognized, Guide IZLT2, File E14853
Withstand Rating: 200,000 RMS Sym. Amps
For use with 22 ≈ 58mm fuses
(FWP-40A22F, FWP-100A22F, etc.)
Materials: Thermoplastic
UL Flammability: UL 94V0
Catalog Numbers
Box Lug w/ Fig. WireAmps Poles Retaining Clip No. Range
1 J70100-1CR 1 #2-14 CU/AL
100 2 J70100-2CR 2 #2-14 CU/AL
3 J70100-3CR 3 #2-14 CU/AL
2.250
3.202
.750
4.702
2.250
CL
L
1.500
4.005
C
2.415
Dimensional Data
100A
.750
1.702
FIGURE 1 FIGURE 2 FIGURE 3
57For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Bussmann®Fuseblocks, Holders and Terminal Blocks
Class J (Finger-Safe) Fuseholders
JT(N)60030 and JT(N)60060For use with Bussmann Class “J” fuses - (Bussmann LPJ, JKS)
Catalog Numbers:
JT60030 and JT60060 - Non-Indicating
JTN60030 and JTN60060 - Indicating (Neon)
Construction: Thermoplastic, UL Flammability; 94VO
Voltage Ratings: 600V
Amperage Rating: JT(N)60030 - 30A,
JT(N)60060 - 60A
Withstand Rating: 200,000A RMS Sym.
(Self Certified at 300,000A using Bussmann
LPJ_SP fuses)
Agency Information:
Listed to UL 512: Guide IZLT, File 14853
CSA Certified: Class 6225-01, File 47235
Indication: Min. voltage: 90 VAC, 115 VDC; Neon Lamp
“ON” when fuse opens, voltage source and current path
are present.
Finger-Safe: IP20 per IEC 60529
Terminations: 30A Dual Port Torque 20 lb. in.,
60A Single Port Torque 45 lb. in., Terminal Construction,
Tin plated Copper Alloy
Wire Size: JT(N)60030 - Rated for 75°C, AWG#18-#8;
CU only, JT(N)60060 - Rated for 75°C, AWG#14-#4;
CU only.
(Note: For JT(N)60030 use both stranded or solid, in a variety of
dual wire combinations of same wire size and type.)
Packaging: 12 in a carton
Safety J
1.14
(29.0)
1.05
(26.7)
Slot
MOUNTING
Shown without fuse
pullout cover
BUSS
0 – 30A600VACUSE CLASS J
FUSES
DO NOT REMOVEUNDER LOAD
JT60030
BUSS
0 – 30A600VACUSE CLASS J
FUSES
DO NOT REMOVEUNDER LOAD
JT60030
BUSS
0 – 30A600VACUSE CLASS J
FUSES
DO NOT REMOVEUNDER LOAD
JT60030
3.60
(91.4)
2.42
(61.3)
1.23
(31.2)
.07
(1.8)1 pole
2 pole
3 pole
2.75
(69.9)
2.52
(64.1)
Din-rail
Dim. = in.
(mm.) JT60030
JTN60030
CE logo denotes compliance with European Union Low Voltage Directive(50-1000Vac, 75-1500Vdc). Refer to Data Sheet: 8002 or contactBussmann Application Engineering at 636-527-1270 for more information.
Data Sheet: 1152
Bussmann®Fuseblocks, Holders and Terminal Blocks
58 For complete specification data, call Bussmann Information Fax ~ 636.527.1450
Class J (Finger-Safe) Fuseholders
JT(N)600 Series fuseblocks can be dovetailed together within the same current rating to provide multiple pole block
configurations.
NOTE: JT(N)60030 cannot be dovetailed to JT(N)60060.
JT60060
JTN60060
Dim. = in.
(mm.)
3.10
(78.7)
3.06
(77.7)
1.31
(33.3)
1.25
(31.8)
Din-railSlot
MOUNTING
Shown without fusepullout cover
4.40
(111.7)
2.96
(75.2)
1.52
(38.1)
.10
(2.6)
BUSS
35 – 60A600VACUSE CLASS J
FUSES
DO NOT REMOVEUNDER LOAD
JT60060
BUSS
35 – 60A600VACUSE CLASS J
FUSES
DO NOT REMOVEUNDER LOAD
JT60060
BUSS
35 – 60A600VACUSE CLASS J
FUSES
DO NOT REMOVEUNDER LOAD
JT60060
1 pole
2 pole
3 pole
Data Sheet: 1152
Bussmann®
227
LPJ (600V), Class J Fuses
Time-Current & Current Limitation Curves
AMPERERATING1
A
3A
5A
10A
15A
20A
30A
40A
50A
60A
300
100
10
1
.1
.01
TIM
E I
N S
EC
ON
DS
10
,00
0
1,0
00
10
0
101
RMS SYMMETRICAL CURRENT IN AMPERES
100A
125A
200A
225A
400A
600A
INS
TA
NTA
NE
OU
S P
EA
K L
ET-T
HR
U C
UR
RE
NT
IN
AM
PS 100,000
10,000
1,000
100
B
A
PROSPECTIVE SHORT-CIRCUIT CURRENTSYMMETRICAL RMS AMPS
10
0
1,0
00
10
,00
0
10
0,0
00
20
0,0
00
600A400A
200A
100A60A50A40A30A20A
15A
AM
PE
RE
RA
TIN
G
Time-Current Characteristic Curves—
Average Melt
Current Limitation Curves
LPJLPJ
Ampere
The measurement of intensity of rate of flow of
electrons in an electric circuit. An ampere is
the amount of current that will flow through a
resistance of one ohm under a pressure of one
volt.
Ampere Rating
The current-carrying capacity of a fuse. When
a fuse is subjected to a current above its
ampere rating, it will open the circuit after a
predetermined period of time.
Ampere Squared Seconds, l2t
The measure of heat energy developed within
a circuit during the fuse’s clearing. It can be
expressed as “melting l2t”, “arcing l2t” or the
sum of them as “Clearing l2t”. “l” stands for
effective let-through current (RMS), which is
squared, and “t” stands for time of opening, in
seconds.
Arcing Time
The amount of time from the instant the fuse
link has melted until the overcurrent is inter-
rupted, or cleared.
Breaking Capacity
(See Interrupting Rating)
Cartridge Fuse
A fuse consisting of a current responsive ele-
ment inside a fuse tube with terminals on both
ends.
Class CC Fuses
600V, 200,000A interrupting rating, branch
circuit fuses with overall dimensions of ⁄‹Ω£™∑ ≈
1⁄Ω™∑. Their design incorporates a rejection
feature that allows them to be inserted into
rejection fuse holders and fuse blocks that
reject all lower voltage, lower interrupting rat-
ing ⁄‹Ω£™∑ ≈ 1⁄Ω™∑ fuses. They are available from
⁄Ω¡ºA through 30A.
Class G Fuses
480V, 100,000A interrupting rating branch cir-
cuit fuses that are size rejecting to eliminate
overfusing. The fuse diameter is ⁄‹Ω£™∑ while
the length varies from 1fiΩ¡§∑ to 2⁄Ω¢∑. These are
available in ratings from 1A through 60A.
Class H Fuses
250V and 600V, 10,000A interrupting rating
branch circuit fuses that may be renewable or
non-renewable. These are available in ampere
ratings of 1 amp through 600A.
Class J Fuses
These fuses are rated to interrupt a minimum
of 200,000A ac. They are labelled
as “Current-Limiting”, are rated for 600vac,
and are not interchangeable with other class-
es.
Class K Fuses
These are fuses listed as K-1, K-5, or K-9
fuses. Each subclass has designated I2t and lpmaximums. These are dimensionally the same
as Class H fuses, and they can have interrupt-
ing ratings of 50,000, 100,000, or 200,000 A.
These fuses are current-limiting. However,
they are not marked “current-limiting” on their
label since they do not have a rejection fea-
ture.
Class L Fuses
These fuses are rated for 601 through 6000A,
and are rated to interrupt a minimum of
200,000A ac. They are labelled “Current-
Limiting” and are rated for 600Vac. They are
intended to be bolted into their mountings and
are not normally used in clips. Some Class L
fuses have designed in time-delay features for all
purpose use.
Class R Fuses
These are high performance fuses rated ⁄Ω¡º-
600A in 250V and 600V ratings. All are
marked “Current Limiting” on their label
and all have a minimum of 200,000A inter-
rupting rating. They have identical outline
dimensions with the Class H fuses but have a
rejection feature which prevents the user from
mounting a fuse of lesser capabilities (lower
interrupting capacity) when used with special
Class R Clips. Class R fuses will fit into either
rejection or non-rejection clips.
Class T Fuses
An industry class of fuses in 300V and 600V
ratings from 1 amp through 1200A. They are
physically very small and can be applied
where space is at a premium. They are fast
acting and time-lag fuses, with an interrupting
rating of 200,000A RMS.
Classes of Fuses
The industry has developed basic physical
specifications and electrical performance
requirements for fuses with voltage ratings of
600V or less. These are known as standards.
If a type of fuse meets the requirements of a
standard, it can fall into that class. Typical
classes are K, RK1, RK5, G, L, H, T, CC, and J.
Clearing Time
The total time between the beginning of the
overcurrent and the final opening of the circuit
at rated voltage by an overcurrent protective
device. Clearing time is the total of the melt-
ing time and the arcing time.
Current Limitation
A fuse operation relating to short circuits only.
When a fuse operates in its current-limiting
range, it will clear a short circuit in less than ⁄Ω™
cycle. Also, it will limit the instantaneous peak
let-through current to a value substantially
less than that obtainable in the same circuit if
that fuse were replaced with a solid conduc-
tor of equal impedance.
Dual Element Fuse
Fuse with a special design that utilizes two
individual elements in series inside the fuse
tube. One element, the spring actuated trig-
ger assembly, operates on overloads up to
5-6 times the fuse current rating. The other
element, the short circuit section, operates on
short circuits up to their interrupting rating.
Electrical Load
That part of the electrical system which actu-
ally uses the energy or does the work
required.
Fast Acting Fuse
A fuse which opens on overload and short
circuits very quickly. This type of fuse is not
designed to withstand temporary overload
currents associated with some electrical
loads.
Fuse
An overcurrent protective device with a fusible
link that operates and opens the circuit on an
overcurrent condition.
High Speed Fuses
Fuses with no intentional time-delay in the
overload range and designed to open as
quickly as possible in the short-circuit range.
These fuses are often used to protect solid-
state devices.
Inductive Load
An electrical load which pulls a large amount
of current—an inrush current—when first
energized. After a few cycles or seconds the
current “settles down” to the full-load running
current.
Interrupting Capacity
See Interrupting Rating
Interrupting Rating
(Breaking Capacity)
The rating which defines a fuse’s ability to
safely interrupt and clear short circuits. This
rating is much greater than the ampere rating
of a fuse. The NEC® defines Interrupting
Rating as “The highest current at rated volt-
age that an overcurrent protective device is
intended to interrupt under standard test
conditions.”
Melting Time
The amount of time required to melt the fuse
link during a specified overcurrent. (See
Arcing Time and Clearing Time.)
“NEC” Dimensions
These are dimensions once referenced in the
National Electrical Code. They are common to
Class H and K fuses and provide inter-
changeability between manufacturers for
fuses and fusible equipment of given ampere
and voltage ratings.
Ohm
The unit of measure for electric resistance. An
ohm is the amount of resistance that will allow
one ampere to flow under a pressure of one
volt.
Bussmann®
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Glossary of Terms