High Speed Fuses
British BS 88 Fuses
High Speed
Fuses
General Information
Introduction
British BS 88 Contents
Fuse
Amp
Volts
Range
240
6-900
690
6-710
Page
188-190
191-194
Accessories
Indicator System & Fuse Bases
195
British BS 88 Fuse Ranges
Amps
6-900
6-710
Vac
240
690
Vdc
150
500
Designed and tested to:
• BS 88: Part 4
• IEC 269: Part 4
• UL Recognized
Cooper Bussmann offers the industry’s widest range of
British style semiconductor fuses and accessories.
Cooper Bussmann British style products use innovative arc
quenching techniques and high grade materials to provide:
• Minimal energy let-through (I2t)
• Excellent DC performance
• Good surge withstand profile
British style fuses are typically found in equipment
manufactured in the United Kingdom or British
Commonwealth countries. However, North American
manufacturers have begun to specify British style fuses —
particularly in UPS applications at 240V or less — to take
advantage of their size, performance and cost benefits.
Voltage Rating
All Cooper Bussmann British style fuses are tested to IEC
269: Part 4. This standard requires a test voltage which is 5%
higher than the rated voltage. In North America, fuses are
required to clear only their rated voltage.
Accessories
Trip-indicator fuses are available for use in parallel with the
main fuse. Indicator fuses can be attached to the associated
fuselink, or mounted separately in panel-mounted fuseclips.
In addition, a push-on adapter and microswitch attachment
are available, to provide remote indication. Fuse blocks are
also available for most applications.
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
187
High Speed Fuses
British BS 88 — 240V: 6-900A
LCT, LET, LMT, LMMT
Arc Voltage
Specifications
Description: BS 88 style
stud-mount fuses.
Dimensions: See dimensions
illustrations.
Ratings:
Volts: — 240Vac/150Vdc
Amps: — 6-900A
IR: — 200kA RMS Sym.
Agency Information: CE, Designed and tested to: BS 88
Part 4, IEC 269 Part 4, UL Recognized. All fuses above have
been tested at 318Vac. Consult Cooper Bussmann for
specific UL Recognition status.
Electrical Characteristics
1.6
Total Clearing I2t
K
1.4
The total clearing I2t at rated
voltage and at power factor
of 15% are given in the
electrical characteristics. For
other voltages, the clearing
I2t is found by multiplying by
correction factor, K, given as
a function of applied working
voltage, Eg, (rms).
1.2
1.0
0.8
0.4
2)
Eg
50
100
150
200
250
Fig. 2: LET
7.1
4
5.5
26.2 41.8 56
28 38 47
9.7
12.7
6.4
17.7
8.4
19.1
8.7
Fig. 4: LMMT
Fig. 3: LMT
1mm = 0.0394” / 1” = 25.4mm
25.4
25.4
31 59
31
59
84
13.5
13.5
10.3
10.3
41
83
38.1
Indicator (Optional)
1)
500
2)
250
Eg
100
Watts loss at rated current
is given in the electrical
characteristics. The curve
allows the calculation of
the power losses at load
currents lower than the
rated current. The correction factor, Kp, is given as
a function of the RMS load
current, Ib, in % of the
rated current.
300
1.0
Kp
0.8
0.6
0.5
0.4
0.3
0.2
Ib
0.1
30 40 50
38
84
Catalog
Numbers
6LCT
10LCT
12LCT
16LCT
20LCT
25LET
32LET
35LET
50LET
63LET
80LET
100LET
125LET
160LET
180LETa
160LMT
200LMT
250LMT
315LMT
355LMT
400LMT
450LMT
400LMMT
500LMMT
630LMMT
710LMMT
800LMMT
900LMMT
Type
LCT
LET
LMT
LMMT
Rated
Current
RMS-Amps
6
10
12
16
20
25
32
35
50
63
80
100
125
160
180
160
200
250
315
355
400
450
400
500
630
710
800
900
Pre-arc
2
3.8
7
20
25
18
32
50
100
180
300
600
600
1100
1600
1100
1500
3200
6000
8000
14000
18000
6000
14000
24000
32000
52000
75000
60
70
80 90 100%
I2t (A2 Sec)
Clearing
at 120V
6
12
22
50
80
120
200
320
500
1100
1900
3800
3800
7000
12000
7000
10000
20000
35000
50000
70000
100000
35000
80000
150000
200000
300000
400000
Clearing
at 240V
9
22
32
100
160
250
450
600
1400
2200
3800
7500
7500
16000
29000
16000
20000
40000
75000
100000
160000
220000
80000
170000
300000
460000
600000
800000
Watts
Loss
1.0
2.5
2.5
2.5
4.0
4.0
5.0
5.0
7.0
9.0
10.0
10.0
16.0
20.0
21.0
17.0
28.0
28.0
35.0
35.0
40.0
42.0
60.0
64.0
75.0
77.0
82.0
97.0
• Watts loss provided at rated current.
• Note: 7LET, 10LET, 12LET and 16LET are available for replacement purposes on existing
equipment.
• See accessories on page 195.
Features and Benefits
• Excellent cycling capability
• Excellent DC performance
• Low arc voltage and low
energy let-through (I2t)
Typical Applications
• DC common bus
• AC and DC drives
• Power converters/rectifiers
• Reduced voltage starters
Data Sheet: 720004
188
200
1) LCT
2) LET, LMT, LMMT
Electrical Characteristics
1)
0.2
UL
Power Losses
Catalog Numbers
0.6
1) LCT
2) LET, LMT, LMMT
Dimensions (mm)
Fig. 1: LCT
750
This curve gives the peak
arc voltage, UL, which
may appear across the
fuse during its operation
as a function of the
applied working voltage,
Eg, (rms) at a power factor
of 15%.
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
High Speed Fuses
British BS 88 — 240V: 6-900A
LCT 6-20A: 240V
LET 25-180A: 240V
Time-Current Curve
Time-Current Curve
104
6
4
104
6
4
2
2
103
103
6
4
6
4
2
6LCT
10LCT
12LCT
16LCT
20LCT
102
6
4
2
102
2
Virtual Pre-Arcing Time In Seconds
2
101
6
4
2
100
6
4
2
10–1
101
6
4
25LET
32LET
35LET
50LET
63LET
2
100
6
4
High Speed
Fuses
2
10–1
6
4
6
4
2
2
10–2
10–2
6
4
6
4
2
2
10–3
6
4
10–3
6
4
2
2
10–4
2
4
6
8
2
4
6 8
101
102
Prospective Current In Amps RMS
2
4
6
8
10–4
103
2
101
4
6
8 102
2
4
6
8 103
Prospective Current In Amps RMS
Data Sheet: 35785296
Data Sheet: 35785293
Peak Let-Through Curve
2
105
900LMMT
800LMMT
710LMMT
630LMMT
450LMT
400 & 500LMMT
355LMT
315LMT
250LMT
6
4
2
104
180LET
200LMT
160LET & LMT
125 & 100LET
80LET
6
Peak Let-Through Current
Virtual Pre-Arcing Time In Seconds
80LET
100LET
125LET
160LET
180LETa
6
4
4
2
103
6
4
63LET
50LET
35LET
32LET
25LET
2
10
2
20LCT
16LCT
12LCT
10LCT
6LCT
6
4
2
SYMMETRICAL FAULT
FULLY ASYMMETRICAL FAULT
101
101
2
4
6
102
2
4
6
103
2
4
6
104
2
4
6
105
Prospective Short-Circuit Current Symmetrical RMS
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
189
High Speed Fuses
British BS 88 — 240V: 6-900A
LMT 160-450A: 240V
LMMT 400-900A: 240V
Time-Current Curve
Time-Current Curve
104
6
4
104
6
4
2
2
103
103
6
4
6
4
2
101
6
4
400LMMT
500LMMT
630LMMT
710LMMT
800LMMT
900LMMT
102
6
4
Virtual Pre-Arcing Time In Seconds
2
Virtual Pre-Arcing Time In Seconds
2
160LMT
200LMT
250LMT
315LMT
355LMT
400LMT
450LMT
102
6
4
2
100
6
4
2
10–1
6
4
2
101
6
4
2
100
6
4
2
10–1
6
4
2
2
10–2
6
4
10–2
6
4
2
2
10–3
10–3
6
4
6
4
2
2
10–4
102
2
4
6
8 103
2
4
6
10–4
8 104
2
102
Prospective Current In Amps RMS
4
6
8 103
2
Data Sheet: 35785294
Data Sheet: 35785295
Peak Let-Through Curve
2
105
900LMMT
800LMMT
710LMMT
630LMMT
450LMT
400 & 500LMMT
355LMT
315LMT
250LMT
6
4
2
10
4
180LET
200LMT
160LET & LMT
125 & 100LET
80LET
Peak Let-Through Current
6
4
2
103
6
4
63LET
50LET
35LET
32LET
25LET
2
102
20LCT
16LCT
12LCT
10LCT
6LCT
6
4
2
SYMMETRICAL FAULT
FULLY ASYMMETRICAL FAULT
101
10
1
2
4
6
102
2
4
6
103
2
4
6
104
2
4
6
105
Prospective Short-Circuit Current Symmetrical RMS
190
4
Prospective Current In Amps RMS
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
6
8 104
High Speed Fuses
British BS 88 — 690V: 6-710A
CT, ET, FE, EET, FEE, FM, FMM, MT, MMT
Arc Voltage
This curve gives the
peak arc voltage, UL,
which may appear
across the fuse during its
operation as a function
of the applied working
voltage, Eg, (rms) at a
power factor of 15%.
Specifications
Description: BS 88 style
stud-mount fuses.
Dimensions: See dimensions
illustrations.
Ratings:
Volts: — 690Vac/500Vdc
Amps: — 6-710A
IR: — 200kA RMS Sym.
Agency Information: CE, Designed and tested to: BS 88
Part 4, IEC 269 Part 4, UL Recognized. MT and MMT —
350Vdc (IEC) rating. Consult Cooper Bussmann for UL
Recognition status.
1.2
1.0
0.8
0.6
1)
2)
0.2
Eg
200
300
400
500
Fig. 2: ET, FE
Eg
400
600 660
1) CT
2) ET, FE, EET, FEE, FM, FMM
1.0
Kp
0.8
0.6
0.5
0.4
0.3
0.2
Ib
0.1
30 40 50
60
•
•
•
•
Typical Applications
DC common bus
DC drives
Power converters/rectifiers
Reduced voltage starters
Fig. 4: FM, MT
8.7
Fig. 5: FMM, MMT
25.4
4
80 90 100%
70
Features and Benefits
Excellent cycling capability
Excellent DC performance
Low arc voltage and low energy let-through (I2t)
Low watts loss
Fig. 3: EET, FEE
7.1
500
•
•
•
•
600 690
1) CT, ET, EET, FE, FEE, MT, MMT
2) FM, FMM
Dimensions (mm)
Fig. 1: CT
2)
High Speed
Fuses
K
1.4
0.4
1000
200
Watts loss at rated
current is given in the
electrical characteristics.
The curve allows the
calculation of the power
losses at load currents
lower than the rated
current. The correction
factor, Kp, is given as a
function of the RMS load
current, Ib, in % of the
rated current.
Total Clearing I2t
1.6
1)
Power Losses
Electrical Characteristics
The total clearing I2t at rated
voltage and at power factor
of 15% are given in the
electrical characteristics. For
other voltages, the clearing
I2t is found by multiplying by
correction factor, K, given as
a function of applied working
voltage, Eg, (rms).
UL
1500
25.4
5.5
50
46 70 94
48 63.5 77
50
54.8 64.3 74.6
A
6.4
8.7
8.7
13.5
19.1
10.3
31.8
10.3
37
19
41
38.1
1mm = 0.0394” / 1” = 25.4mm
Data Sheet: 720024
113
14
11.9
9.7
12.7
17.1
A
113
83
38
Figs. 4 & 5 “A” Dimensions
Type
“A”
FM
80-85mm
FMM
80-85mm
MT
85mm
MMT
85mm
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
191
High Speed Fuses
British BS 88 — 690V: 6-710A
Catalog Numbers
CT
ET
FE
EET
FEE
FM
FMM
MT
MMT
CT 6-20, ET 25-80A: 690V
Watts
Loss
2
3
3
7
7
7
11
11
9
11
14
16
18
9
9
11
11
12
17
20
20
23
19
27
35
39
24
32
36
46
46
52
40
40
44
48
48
55
55
85
90
100
100
100
120
26
26
27
32
35
42
51
42
42
42
47
51
54
60
57
64
64
86
105
• Watts loss provided at rated current.
• Note: FC, 8ET, 12ET, 15ET, 20ET, 65EET and 75EET are available for replacement
purposes on existing equipment.
• See accessories on page 195.
Time-Current Curve
104
6
4
2
103
6
4
25ET
32ET
35ET
40ET
45ET
56ET
63ET
80ET
2
102
6
4
Virtual Pre-Arcing Time In Seconds
Type
Electrical Characteristics
I2t (A2 Sec)
Clearing Clearing
Pre-arc
at 415V
at 660V
1.8
8.5
12
7
30
48
10
40
65
16
66
110
32
150
220
25
150
250
32
190
350
52
310
500
103
600
900
103
680
1100
135
950
1500
171
1200
2000
360
2500
4000
33
130
200
52
180
300
76
270
450
103
380
600
135
480
750
210
600
950
250
900
1500
360
1300
2100
470
1800
2800
490
3000
4500
600
4000
6500
1050
7000
12000
1500
10000
17000
400
1600
2400
540
1900
3100
850
2500
3800
1000
3700
5700
1400
5300
8400
1900
7100
11400
1400
7500
13500
2600
10500
18500
3700
14500
26500
5200
20500
37500
7000
30500
55000
10000
40000
77000
15000
60000
105000
10000
40000
72500
15000
60000
105000
20000
82000
150000
30000
120000
215000
45000
180000
310000
60000
245000
420000
2400
15000
25000
3800
25000
38000
6000
40000
58000
11500
80000
110000
16500
100000
150000
19000
125000
180000
22000
160000
200000
1650
12000
18000
2200
16000
23000
3700
26000
40000
6600
47000
70000
8600
62000
91000
13500
97000
140000
21000
150000
220000
30000
220000
320000
42000
300000
450000
60000
430000
640000
68500
500000
720000
78000
600000
850000
2
101
6
4
6CT
10CT
12CT
16CT
20CT
2
100
6
4
2
10–1
6
4
2
10–2
6
4
2
10–3
6
4
2
10–4
2
4
6
8 101
2
4
6
8 102
2
6
8 103
Peak Let-Through Curve
6
4
2
315MT 355MT
280MT
250MT
105
6
180MT
160MT
4
710MMT
630MMT
560MMT
500MMT
450MMT
400MMT
355MMT
315MMT
280MMT
200MT
225MMT
200MMT
180MMT
2
104
6
4
2
103
6
160EET
140EET
110EET
90EET
4
80ET
63ET
56ET
45ET
40ET
35ET
32ET
25ET
2
20CT
16CT
12CT
10CT
6CT
102
6
4
2
101
101
2
4
6
102
2
4
6
103
2
4
6
104
Prospective Short-Circuit Current Symmetrical RMS
Data Sheet: 35785312
192
4
Prospective Current In Amps RMS
Peak Let-Through Current
Catalog
Numbers
6CT
10CT
12CT
16CT
20CT
25ET
32ET
35ET
40ET
45ET
56ET
63ET
80ET
35FE
40FE
45FE
50FE
63FE
71FE
80FE
90FE
100FE
90EET
110EET
140EET
160EET
100FEE
120FEE
140FEE
160FEE
180FEE
200FEE
180FM
200FM
225FM
250FM
280FM
315FM
350FM
400FMM
450FMM
500FMM
550FMM
630FMM
700FMM
160MT
180MT
200MT
250MT
280MT
315MT
355MT
180MMT
200MMT
225MMT
280MMT
315MMT
355MMT
400MMT
450MMT
500MMT
560MMT
630MMT
710MMT
Rated
Current
RMS-Amps
6
10
12
16
20
25
32
35
40
45
56
63
80
35
40
45
50
63
71
80
90
100
90
110
140
160
100
120
140
160
180
200
180
200
225
250
280
315
350
400
450
500
550
630
700
160
180
200
250
280
315
355
180
200
225
280
315
355
400
450
500
560
630
710
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
2
4
6
105
2
High Speed Fuses
British BS 88 — 690V: 6-710A
EET 90-160A, MT 160-355A: 690V
MMT 180-710A: 690V
Time-Current Curve
Time-Current Curve
104
104
6
4
6
4
2
2
103
160MT
180MT
200MT
250MT
280MT
315MT
355MT
6
4
2
102
6
4
6
4
2
102
6
4
Virtual Pre-Arcing Time In Seconds
2
101
6
4
90EET
110EET
140EET
160EET
2
100
6
4
2
10
–1
6
4
6
4
2
100
6
4
2
10–1
6
4
2
10–2
2
6
4
10–2
2
6
4
10–3
6
4
2
10–3
2
10–4
180MMT
200MMT
225MMT
280MMT
315MMT
355MMT
2
101
High Speed
Fuses
2
4
6
8 102
2
4
6
8 103
2
4
6
6
4
8 104
2
Prospective Current In Amps RMS
10–4
2
102
4
6 8
2
4
103
Prospective Current In Amps RMS
Data Sheet: 35785313
6
8
104
Data Sheet: 35785311
Peak Let-Through Curve
6
4
2
315MT 355MT
280MT
250MT
105
6
180MT
160MT
4
710MMT
630MMT
560MMT
500MMT
450MMT
400MMT
355MMT
315MMT
280MMT
200MT
225MMT
200MMT
180MMT
2
Peak Let-Through Current
Virtual Pre-Arcing Time In Seconds
400MMT
450MMT
500MMT
560MMT
630MMT
710MMT
103
104
6
4
2
103
6
160EET
140EET
110EET
90EET
4
80ET
63ET
56ET
45ET
40ET
35ET
32ET
25ET
2
20CT
16CT
12CT
10CT
6CT
102
6
4
2
101
101
2
4
6
102
2
4
6
103
2
4
6
104
2
4
6
105
2
Prospective Short-Circuit Current Symmetrical RMS
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
193
High Speed Fuses
British BS 88 — 690V: 6-710A
FE 35-100A & FM 180-350A: 690V
FEE 100-200A & FMM 400-700A: 690V
Time-Current Curve
Time-Current Curve
104
104
6
4
6
4
2
2
103
6
4
103
6
4
2
180FM
200FM
220FM
250FM
280FM
315FM
350FM
2
101
6
4
2
2
35FE
40FE
45FE
50FE
63FE
71FE
80FE
90FE
100FE
100
6
4
2
10–1
6
4
2
101
6 100FEE
4 120FEE
140FEE
2 160FEE
180FEE
100 200FEE
6
4
2
10–1
6
4
2
10–2
6
4
2
10–2
6
4
2
10–3
6
4
2
2
10–4
400FMM
450FMM
500FMM
550FMM
630FMM
700FMM
102
6
4
Virtual Pre-Arcing Time In Seconds
Virtual Pre-Arcing Time In Seconds
102
6
4
2
4
6
8 102
2
4
6
8 103
2
4
6
8 104
10–3
6
4
Prospective Current In Amps RMS
2
10–4
2
102
Peak Let-Through Curve
4
6 8
2
4
103
Prospective Current In Amps RMS
630FMM
6
550FMM
4
500FMM
450FMM
4
2
6
2
Peak Let-Through Current
4
Peak Let-Through Current
400FMM
350FM
315FM
280FM
250FM
225FM
200FM
180FM
104
2
103
6
4
2
100FE
90FE
80FE
71FE
63FE
50FE
45FE
40FE
35FE
102
6
4
104
8
6
4
2
103
200FEE
8
2
180FEE
6
2
4
6
102
2
4
6
103
2
4
6
104
2
4
6
105
2
160FEE
140FEE
4
120FEE
100FEE
Prospective Short-Circuit Current Symmetrical RMS
2
102
2
4
6
103
2
4
6
104
2
4
Prospective Short-Circuit Current Symmetrical RMS
Data Sheet: 35785314
194
104
700FMM
8
6
101
8
Peak Let-Through Curve
105
101
6
Data Sheet: 35785292
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
6
105
2
High Speed Fuses
British BS 88 Fuse Accessories
Indicator System
CL1 Panel Mount Clips
Trip-Indicators
CL1 Panel mount fuse clips
are available for mounting a
trip-indicator when mounting
directly on the fuse is
impractical. Order part
number CL1.
Trip-indicators are available for use in parallel with the
main fuse. They can either be attached to the associated
fuse or mounted separately in panel mounted fuse clips,
reference CL1. A push-on adapter and microswitch
attachment is available for use with the trip indicator to
give the facility of remote indication, reference MAI.
Fuse ratings of 20A and below cannot usually
accommodate a trip-indicator.
Trip-Indicator
Dimensions - mm
Type
Maximum RMS Voltage
Maximum Peak Voltage
Maximum DC Voltage
Cold Resistance (ohms)
Maximum permissible steady-state current
Interrupting Capacity (RMS Symm.)
Pre-Arcing I2t
TI500
500
700
130
0.3
1.5A
100,000
23
TI700
700
1000
350
0.45
1.5A
100,000
23
Ref.
TI250
TI500
TI600
TI700
TI1100
TI1500
TI2000
TI2500
D
Dim. “A” (mm)
37.6
47.5
55.7
61.8
98.4
120.6
147.5
198.3
CL1 Panel Mount Clip
Dimensions - mm
Fuse Indicator Kits
RMS
Volts
250
250
660
660
700
F
E
0.8
A
Electrical Specifications
Details
Fuse Mount
Indicator Kits
(Includes one
indicator
and two clips)
B
21
C
6
6.35
High Speed
Fuses
When a trip-indicator is to be attached to the main fuse an
accessory pack comprising a pair of mounting clips and an
appropriate trip indicator would be required. The clips are
snapped onto the fuse end caps and the indicator is
pressed into clips as shown.
Kit. Ref.
EC-250
MC250
EC-600
MC600
MC700
Trip
Indicator
6.8
RMS Volts
250
500
600
700
1100
1500
2000
2500
6.0
8.7
14
For use
with Fuse Ref.
LET
LMT & LMMT
FE, FEE & ET
FM & FMM
MT & MMT
50.8
B
Terminal Arrang ement
Microswitch Adapter – MAI
We offer a microswitch, complete with adapter for
securing the indicator. The microswitch is provided with
double pole, single throw contacts, having both a normally
open and a normally closed position. A special material has
been employed in the construction of the adapter to
provide reliable operation in the range of temperatures
associated with standard operating conditions and during
fuse operation.
NO
NC
NC
NO
Dimensions in mm
Microswitch and Adapter Type MAI
Current Rating:
AC 50/60Hz resistive load @ 250V RMS
AC 50/60Hz resistive load @ 127V RMS
DC, resistive load @ 110Vdc
DC, resistive load @ 30Vdc
Maximum Working Voltage:
Contact-to-contact (RMS)
Contact-to-contact (RMS)
Maximum DC Volts:
4A
6A
0.7A DC
2A DC
1000V
1500V
110V DC
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
195