High Speed Fuses
British BS 88 Fuses
High Speed
Fuses
Introduction
British BS 88 Contents
Fuse
Amp
Volts
Range
240
6-900
690
6-710
Accessories
Indicator System & Fuse Bases
British BS 88 Fuse Ranges
Amps
6-900
6-710
Vac
240
690
Vdc
150
500
General Information
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 (I
2
t)
• 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.
Page
188-190
191-194
195
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
187
High Speed Fuses
British BS 88 — 240V: 6-900A
LCT, LET, LMT, LMMT
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
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%.
Power Losses
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 correc-
tion factor, Kp, is given as
a function of the RMS load
current, Ib, in % of the
rated current.
Catalog Numbers
1)
Electrical Characteristics
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
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
750
U
L
1)
500
2)
250
E
g
100
200
300
1) LCT
2) LET, LMT, LMMT
1.0
K
p
0.8
0.6
0.5
0.4
0.3
0.2
Total Clearing I
2
t
The total clearing I t at rated
voltage and at power factor
of 15% are given in the
electrical characteristics. For
other voltages, the clearing
I
2
t is found by multiplying by
correction factor, K, given as
a function of applied working
voltage, Eg, (rms).
2
K
1.4
1.2
1.0
0.8
0.6
0.4
0.2
50
2)
100
150
200
1) LCT
2) LET, LMT, LMMT
E
g
0.1
30 40 50
60
70
I
b
80 90 100%
Type
250
LCT
Dimensions (mm)
Fig. 1: LCT
4
5.5
Fig. 2: LET
7.1
LET
26.2 41.8 56
28 38 47
9.7
12.7
6.4
8.4
8.7
17.7
19.1
Fig. 4: LMMT
25.4
LMT
Fig. 3: LMT
25.4
1mm = 0.0394” / 1” = 25.4mm
31 59
31
59
84
84
LMMT
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
I
2
t (A
2
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
13.5
13.5
10.3
10.3
• 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.
41
83
38.1
Indicator (Optional)
38
Features and Benefits
• Excellent cycling capability
• Excellent DC performance
• Low arc voltage and low
energy let-through (I
2
t)
Typical Applications
• DC common bus
• AC and DC drives
• Power converters/rectifiers
• Reduced voltage starters
Data Sheet: 720004
188
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
High Speed Fuses
British BS 88 — 240V: 6-900A
LCT 6-20A: 240V
Time-Current Curve
10
4
6
4
2
10
3
6
4
2
10
2
6
4
2
Virtual Pre-Arcing Time In Seconds
10
1
6
4
2
10
0
6
4
2
10
–1
LET 25-180A: 240V
Time-Current Curve
10
4
6
4
2
10
3
6
4
6LCT
10LCT
12LCT
16LCT
20LCT
Virtual Pre-Arcing Time In Seconds
2
10
2
6
4
2
10
1
6
4
2
10
0
6
4
2
10
–1
80LET
100LET
125LET
160LET
180LETa
25LET
32LET
35LET
50LET
63LET
High Speed
Fuses
6
4
2
10
–2
6
4
2
10
–3
6
4
2
10
–2
6
4
2
10
–3
6
4
2
10
–4
2
4
6
8
2
4
6 8
10
1
10
2
Prospective Current In Amps RMS
2
4
6
8
10
3
10
6
4
2
–4
10
1
2
4
6
8 10
2
2
4
6
8 10
3
Prospective Current In Amps RMS
Data Sheet: 35785296
Data Sheet: 35785293
Peak Let-Through Curve
2
10
5
6
4
2
10
4
6
Peak Let-Through Current
4
900LMMT
800LMMT
710LMMT
630LMMT
450LMT
400 & 500LMMT
355LMT
315LMT
250LMT
180LET
200LMT
160LET & LMT
125 & 100LET
80LET
2
10
3
6
4
63LET
50LET
35LET
32LET
25LET
20LCT
16LCT
12LCT
10LCT
6LCT
SYMMETRICAL FAULT
FULLY ASYMMETRICAL FAULT
10
1
2
4
6
10
2
2
4
6
10
3
2
4
6
10
4
2
4
6
10
5
2
10
2
6
4
2
10
1
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
Time-Current Curve
10
4
6
4
2
10
3
6
4
2
10
2
6
4
2
Virtual Pre-Arcing Time In Seconds
10
1
6
4
2
10
0
6
4
2
10
–1
LMMT 400-900A: 240V
Time-Current Curve
10
4
6
4
2
10
3
6
4
160LMT
200LMT
250LMT
315LMT
355LMT
400LMT
450LMT
2
10
2
6
4
Virtual Pre-Arcing Time In Seconds
2
10
1
6
4
2
10
0
6
4
2
10
–1
400LMMT
500LMMT
630LMMT
710LMMT
800LMMT
900LMMT
6
4
2
10
–2
6
4
2
10
–2
6
4
2
10
–3
6
4
2
10
–3
6
4
2
10
2
2
4
6
8 10
3
2
4
6
8 10
4
10
–4
6
4
2
10
–4
Prospective Current In Amps RMS
10
2
2
4
6
8 10
3
2
4
6
8 10
4
Prospective Current In Amps RMS
Data Sheet: 35785294
Data Sheet: 35785295
Peak Let-Through Curve
2
10
5
6
4
2
10
4
6
Peak Let-Through Current
4
900LMMT
800LMMT
710LMMT
630LMMT
450LMT
400 & 500LMMT
355LMT
315LMT
250LMT
180LET
200LMT
160LET & LMT
125 & 100LET
80LET
2
10
3
6
4
63LET
50LET
35LET
32LET
25LET
20LCT
16LCT
12LCT
10LCT
6LCT
SYMMETRICAL FAULT
FULLY ASYMMETRICAL FAULT
10
1
2
4
6
10
2
2
4
6
10
3
2
4
6
10
4
2
4
6
10
5
2
10
2
6
4
2
10
1
Prospective Short-Circuit Current Symmetrical RMS
190
For product data sheets, visit www.cooperbussmann.com/datasheets/ulcsa
High Speed Fuses
British BS 88 — 690V: 6-710A
CT, ET, FE, EET, FEE, FM, FMM, MT, MMT
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.
Electrical Characteristics
Total Clearing I
2
t
The total clearing I
2
t at rated
voltage and at power factor
of 15% are given in the
electrical characteristics. For
other voltages, the clearing
I
2
t is found by multiplying by
correction factor, K, given as
a function of applied working
voltage, Eg, (rms).
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
200
1)
K
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%.
Power Losses
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.
1500
U
L
1)
1000
2)
500
E
g
200
400
600 660
1) CT
2) ET, FE, EET, FEE, FM, FMM
1.0
K
p
0.8
0.6
0.5
0.4
0.3
0.2
High Speed
Fuses
0.1
30 40 50
60
70
I
b
80 90 100%
2)
E
g
300
400
500
600 690
Features and Benefits
• Excellent cycling capability
• Excellent DC performance
• Low arc voltage and low energy let-through (I
2
t)
• Low watts loss
Typical Applications
• DC common bus
• DC drives
• Power converters/rectifiers
• Reduced voltage starters
1) CT, ET, EET, FE, FEE, MT, MMT
2) FM, FMM
Dimensions (mm)
Fig. 1: CT
4
5.5
Fig. 2: ET, FE
7.1
Fig. 3: EET, FEE
8.7
Fig. 4: FM, MT
25.4
Fig. 5: FMM, MMT
25.4
48 63.5 77
54.8 64.3 74.6
11.9
9.7
12.7
17.1
8.7
19.1
31.8
37
46 70 94
50
50
A
113
14
13.5
10.3
10.3
A
113
6.4
8.7
19
41
38.1
83
1mm = 0.0394” / 1” = 25.4mm
Data Sheet: 720024
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
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