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12

LLNRK/LLSRK Series POWR-PRO

®

Class RK1 

250/600 VAC

s

Dual-Element, Time-Delay

s

1/10 – 600 Amperes

SPECIFICATIONS

Voltage Ratings: AC: 250 Volts (LLNRK)

600 Volts (LLSRK)

DC: 125 Volts (LLNRK)

300 Volts (LLSRK)

Interrupting Ratings:

AC: 200,000 amperes rms symmetrical

300,000 amperes rms symmetrical 

(Littelfuse self-certified)

DC: 20,000 amperes

Ampere Range: 1/10 – 600 amperes

Approvals:

AC: Standard 248-12, Class RK1

UL Listed (File No: E81895)

CSA Certified (File No: LR29862)

QPL: Federal Specification No. WF-1814

DC: Littelfuse self-certified

AMPERE RATINGS

1

10

1

2

8

10

6

1

4

25

90

300

15

100

1

1

8

3

7

30

100

350

2

10

1

1

4

3

2

10

8

35

110

400

1

4

*

1

4

10

3

1

2

9

40

125

450

3

10

1

6

10

4

10

45

150

500

4

10

1

8

10

4

1

2

12

50

175

600

1

2

2

5

15

60

200

6

10

2

1

4

5

6

10

17

1

2

70

225

8

10

2

1

2

6

20

80

250

* LLSRK Only.

Example part number (series & amperage): LLNRK 450

RECOMMENDED FUSE BLOCKS

LR250 series (LLNRK Series)

LR600 series (LLSRK Series)

Refer to Fuse Block section of this catalog for additional 

information.

FEATURES/BENEFITS

s

Extremely current limiting — Reduces damage to circuits

and equipment under short-circuit conditions. Stops 

damaging short circuits faster than any mechanical 

protective device.

s

300kA Interrupting Rating — Littelfuse self-certified to

300,000 amperes as standard. Meets future trend towards

higher available short circuit currents.

s

Reduced costs — Current limiting design often permits 

use of readily available, less costly equipment. Low 

resistance design reduces power consumption and utility

bills.

s

Excellent time delay — True dual-element construction, 

with separate non-fatiguing thermally-reversible spring-

loaded thermal overload element, withstands repeated

surges within rated time delay without opening needlessly.

Eliminates needless downtime caused by power surges or

equipment demands.

Littelfuse LLNRK and LLSRK series POWR-PRO

®

fuses 

provide superior overload and short circuit protection for 

service entrance, main, feeder and general-purpose branch

circuits up to 600 amperes.

LLNRK/LLSRK series fuses can be installed in existing Class

H fuse blocks to upgrade systems containing lower interrupt-

ing rating Class H one-time or renewable fuses.

APPLICATIONS

All general-purpose circuits

Motors

Transformers

Solenoids

Fluorescent lighting

All system components with high in-rush currents

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13

LLNRK/LLSRK Series POWR-PRO

®

Class RK1 

250/600 VAC

s

Dual-Element, Time-Delay

s

1/10 – 600 Amperes

LLNRK

LLSRK

LLNRK

LLSRK

LLNRK

LLSRK

LLNRK

LLSRK

LLNRK

LLSRK

LLNRK

LLSRK

1

1

2

2

2

2

1/10 – 30

35 – 60

70 – 100

110 – 200

225 – 400

450 – 600

AMPERES

REFER TO

FIG. NO.

SERIES

DIMENSIONS IN INCHES (mm in parentheses)

2

1/2

1/2

9/16

5/64

5/32

3/8

— 

(50.8)

(12.7)

(12.7)

(14.3)

(2.0)

(4.0)

(9.5)

5

3/4

5/8

13/16

3/32

3/16

5/8

(127.0)

(19.1)

(15.9)

(20.6)

(2.4)

(4.8)

(15.9)

3

3/4

5/8

13/16

3/32

3/16

5/8

— 

(76.2)

(19.1)

(15.9)

(20.6)

(2.4)

(4.8)

(15.9)

5-1/2

1

5/8

1-1/16

3/32

1/4

7/8

— 

(139.7)

(25.4)

(15.9)

(27.0)

(2.4)

(6.4)

(22.2)

5-7/8

1

1-1/16

1-1/16

1/8

3/4

1-1/4

1/4

9/32

1/2 

(149.2)

(25.4)

(27.0)

(27.0)

(3.2)

(19.1)

(31.8)

(6.4)

(7.1)

(12.7)

7-7/8

1-1/4

1-1/16

1-5/16

1/8

3/4

1-1/2

1/4

9/32

1/2 

(200.0)

(31.8)

(27.0)

(33.3)

(3.2)

(19.1)

(38.1)

(6.4)

(7.1)

(12.7)

7-1/8

1-1/2

1-15/32

1-19/32

3/16

1-1/8

1-27/32

7/16

9/32

11/16 

(181.0)

(38.1)

(37.3)

(40.5)

(4.8)

(28.6)

(46.8)

(11.1)

(7.1)

(17.5)

9-5/8

1-3/4

1-15/32

1-27/32

3/16

1-1/8

2-3/32

7/16

9/32

11/16 

(244.5)

(44.5)

(37.3)

(46.8)

(4.8)

(28.6)

(53.2)

(11.1)

(7.1)

(17.5)

8-5/8

2

1-15/16

2-3/32

1/4

1-5/8

2-11/32

5/8

13/32

15/16 

(219.1)

(50.8)

(49.2)

(53.2)

(6.4)

(41.3)

(59.5)

(15.9)

(10.3)

(23.8)

11-5/8

2-1/2

2

2-19/32

1/4

1-5/8

2-27/32

5/8

13/32

15/16 

(295.3)

(63.5)

(50.8)

(65.9)

(6.4)

(41.3)

(72.2)

(15.9)

(10.3)

(23.8)

10-3/8

2-1/2

2-3/8

2-19/32

1/4

2

2-27/32

3/4

17/32

1-1/8 

(263.5)

(63.5)

(60.3)

(65.9)

(6.4)

(50.8)

(72.2)

(19.1)

(13.5)

(28.6)

13-3/8

3

2-13/32

3-3/32

1/4

2

3-11/32

3/4

17/32

1-1/8 

(339.7)

(76.2)

(61.1)

(78.6)

(6.4)

(50.8)

(84.93)

(19.1)

(13.5)

(28.6)

A

B

C

D

E

F

G

H

J

K

A

F

E

C

D

G

B

A

J

K

H

B

C

F

D

G

70-600A

FIG. 1

FIG. 2

E

1000

800

600

400

300

200

100

80

60

40

30

20

10

8

6

4

3

2

1

.8

.6

.4

.3

.2

.1

.08

.06

.04

.03

.02

.01

200

300

400

600

800

1000

2000

3000

4000

6000

8000

10000

20000

30000

40000

60000

80000

100000

8

10

20

30

40

60

80

100

5

15A

30A

60A

100A

200A

400A

600A

TIME IN SECONDS

CURRENT IN AMPERES

1000

800

600

400

300

200

100

80

60

40

30

20

10

8

6

4

3

2

1

.8

.6

.4

.3

.2

.1

.08

.06

.04

.03

.02

.01

200

300

400

600

800

1000

2000

3000

4000

6000

8000

10000

20000

30000

40000

60000

80000

100000

8

10

20

30

40

60

80

100

5

15A

30A

60A

100A

200A

400A

600A

TIME IN SECONDS

CURRENT IN AMPERES

LLNRK

LLSRK

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14

LLNRK/LLSRK Series POWR-PRO

®

Class RK1 

250/600 VAC

s

Dual-Element, Time-Delay

s

1/10 – 600 Amperes

Current-Limiting Effects 

of LLSRK (600V) fuses

* Prospective RMS Symmetrical Amperes Short-Circuit Current

** Apparent RMS Symmetrical

Note: Data derived from Peak Let-Thru Curves

Short

Peak Let-Thru Current**

Circuit

for various fuse ratings

Current*

30A

60A

100A

200A

400A

600A

5,000

1,060

1,600 2,100 2,600

4,100

10,000

1,350

2,000 2,800 3,400

5,250

8,000

15,000

1,600

2,300 3.200 3,900

6,000

9,000

20,000

1,700

2,600 3,600 4,500

6,700 10,000

25,000

1,900

2,800 3,800 4,800

7,500 11,000

30,000

2,000

3,000 4,100 5,200

8,000 12,000

35,000

2,100

3,100 4,400 5,700

8,500 12,500

40,000

2,200

3,300 4,600 6,000

9,000 13,000

50,000

2,400

3,500 4,900 6,500

9,500 14,000

60,000

2,500

3,800 5,200 7,000 10,000 15,000

80,000

2,700

4,000 5,700 7,750 11,000 17,000

100,000

2,900

4,200 6,200 8,500 12,000 18,000

150,000

3,200

4,600 7,300 10,000 14,000 21,000

200,000

3,300

4,700 8,000 11,000 16,000 23,000

2000

3000

4000

6000

8000

10000

20000

30000

40000

60000

80000

100000

200000

100

200

300

400

600

800

1000

100

200

300

400

600

800

1000

2000

3000

4000

6000

8000

10000

20000

30000

40000

60000

80000

100000

200000

300000

400000

600000

800000

1000000

600A

400A

200A

100A

60A

30A

PEAK LET

-THR

U IN AMPERES

AVAILABLE FAULT CURRENT

SYMMETRICAL  R. M. S.  AMPERES

2000

3000

4000

6000

8000

10000

20000

30000

40000

60000

80000

100000

200000

100

200

300

400

600

800

1000

100

200

300

400

600

800

1000

2000

3000

4000

6000

8000

10000

20000

30000

40000

60000

80000

100000

200000

300000

400000

600000

800000

1000000

600A

400A

200A

100A

60A

30A

PEAK LET

-THR

U IN AMPERES

AVAILABLE FAULT CURRENT

SYMMETRICAL  R. M. S.  AMPERES

Current-Limiting Effects 

of LLNRK (250V) fuses

* Prospective RMS Symmetrical Amperes Short-Circuit Current

** Apparent RMS Symmetrical

Note: Data derived from Peak Let-Thru Curves

Short

Peak Let-Thru Current** 

Circuit

for various fuse ratings

Current*

30A

60A

100A

200A

400A

600A

5,000

900

1,400 2,000 2,700

4,800

5,000

10,000

1,100

1,900 2,700 3,500

6,200

8,500

15,000

1,250

2,100 3,100 4,200

7,000

9,500

20,000

1,400

2,400 3,500 4,600

8,000 10,800

25,000

1,500

2,600 3,900 5,000

8,300 11,500

30,000

1,600

2,800 4,000 5,250

9,000 12,000

35,000

1,700

2,850 4,300 5,500

9,500 12,500

40,000

1,800

3,000 4,600 5,800

9,800 13,500

50,000

1,900

3,200 4,800 6,300 10,200 14,000

60,000

2,000

3,500 5,200 6,700 11,000 15,000

80,000

2,200

3,900 5,700 7,200 12,200 16,000

100,000

2,300

4,000 6,000 8,100 12,700 17,000

150,000

2,500

4,500 6,700 9,100 14,000 19,000

200,000

2,600

4,800 7,000 9,700 15,000 20,000

LLNRK

LLSRK