Group: SCHURTER
Catalog excerpts
Fuse Selection White Paper Find the Right Fuse! Criteria for Correct Fuse Selection Circuitry overcurrent protection rarely receives the attention it deserves. An inadequately thought out selection of fuses can lead to the breakdown of equipment and installation, resulting in high replacement costs and dissatisfied customers. This technical article focuses on the correct selection criteria for fuses and fuseholders, and should help you take the more important aspects into consideration. Normal operation after switching ON is explained under Point 1. This Point should always be taken into consideration. Point 2 is only necessary with capacitive loads, present when the charging of capacitors after switching ON, leads to high in-rush current peaks and the rated current of the fuse is exceeded by many multiples. Important facts with regard to fuseholders are given under Point 3, where the correct selection of fuse and fuseholder combinations is explained. Derating of rated current in % Fig. 1: shows the de-rating curve of the time-lag SMD fuse UMT 250. The function of a fuse is to interrupt an uncontrolled fault current or overcurrent before serious damage can occur, such as the overheating of equipment. Because a fuse is designed using a fusing element, it is particularly suited for reliable interruption of short-circuits. With overcurrents up to 2x or 3x the rated current, a fuse becomes less accurate and, as such, not so well suited for these conditions. Other overcurrent protection measures such as electronic protection, thermal overload elements or additional fuses are then necessary. Point 1: Normal Operation After Switching ON Under normal operating conditions, a fuse is subjected to a maximum operating current and a maximum operating temperature. A «derating» of the rated current is therefore usually necessary since a fuse is rarely operated at the set ambient temperature of 23 ˚C. As an example, let’s look at a scenario using a time-lag SMD fuse such as the UMT 250 from SCHURTER. With an operating temperature of 60 ˚C, in accordance with Fig. 1 the fuse needs to be derated by 17%, i.e., when the
Open the catalog to page 1Fuse Selection White Paper operating current is 1 A @ 60 ˚C, a rounded-up fuse value of 1.25A (1A / 0.83) is necessary. Fuses can be in accordance with IEC 60127 or UL 248-14. Because of the different definitions between the two standards, fuses are not directly interchangeable as follows: fuses in accordance with IEC 60127 may be operated continually at 100% of the rated current value, whereas fuses in accordance with UL 248-14 only at 75%. UL 248-14 specifies a minimum of 4h operating time at rated current (Table 1). The self-heating effect of time-lag fuses is less than that of...
Open the catalog to page 2Fuse Selection White Paper Variants Order Number Rated Cur- Rated Voltage Rated Voltage rent [A] [VAC] [VDC] Breaking Capacity Voltage Drop Voltage Drop Power Dis- Melting l2t 10.0 1.0 ln max. 1.0 ln typ. sipation 1.25 ln typ. [A 2s] [mV] [mV] ln typ. [mW] Table 3: Versions of UMT 250 with details of the melting integrals, voltage drops and power losses for every current rating. current peak in excess of this value, the fusing element melts and interrupts the circuit. In our example the I2t value of the fuse (2.8 A2s) is higher than the calculated value (1.748 A2s); that is, the selection...
Open the catalog to page 3Fuse Selection White Paper The fuse power dissipation is calculated with the rated current and typical voltage drop value (voltage level over the fuse at rated current) according to the catalog. Ceramic fuses such as, SPT 5x20, 6.3 A have a typical voltage drop of 70 mV at rated current. Correct dimensioning can be ascertained through the use of the following equation: PFuse= IN*UVoltageDrop_typ Combination is correct layed out, when PFuseholder > PFuse + PContact According to the IEC standard, the contact resistance Rc between fuse and clip is a maximum of 5 mΩ. Power dissipation can be...
Open the catalog to page 4All SCHURTER catalogs and technical brochures
-
FMAD NEO
6 Pages
-
SUSTAINABILITY REPORT 2022
37 Pages
-
THS
5 Pages
-
TTS
4 Pages
-
Product News
4 Pages
-
FMAB NEO
12 Pages
-
FPG1
4 Pages
-
FMAB HV
6 Pages
-
UMT-W
4 Pages
-
OGN
3 Pages
-
0712
3 Pages
-
CPS
7 Pages
-
DG12
10 Pages
-
4751
4 Pages
-
FMAD CP
4 Pages
-
4783
4 Pages
-
EF11
8 Pages
-
PFRY
4 Pages
-
PFRA
6 Pages
-
PFMF
4 Pages
-
PFHT
3 Pages
-
PFDF
3 Pages
-
Company Profile
20 Pages
-
Voltage Selector
1 Pages
-
Resettable Fuses
1 Pages
-
6051.2067
3 Pages
-
6051.2068
3 Pages
-
Suppression Chokes DKIH-1
6 Pages
-
4797-5
4 Pages
-
6051.2063
3 Pages
-
6051.2061
3 Pages
-
6051.2015
3 Pages
-
3-108-993
2 Pages
-
3-100-361
3 Pages
-
GP21
3 Pages
-
AURORA Complete Solutions
2 Pages
-
FMER SOL
10 Pages
-
CMF2, CMF5
3 Pages
-
CDS1
5 Pages
-
DKIH-3
6 Pages
-
4710-5
5 Pages
-
Touchkit
3 Pages
-
USN 1206
3 Pages
-
FPBB RAIL
7 Pages
-
DD14
8 Pages
-
VAC19KS
3 Pages
-
UMK 250
4 Pages
-
TA35 Rocker 1Pole
6 Pages
-
4761
3 Pages
-
4732
4 Pages
-
FUS
3 Pages
-
DKIH
6 Pages
-
FSO
2 Pages
-
CSO
3 Pages
-
CMF1, CMF4
3 Pages
-
FMAC NEO
5 Pages
-
MSM DP 30
8 Pages
-
PSE AE 16
3 Pages
-
MSM LA CS 22
7 Pages
-
MSM LA CS 19
6 Pages
-
PSE AE 30
5 Pages
-
PSE EX 16
5 Pages
-
PSE EX 19
5 Pages
-
PSE NO 19
6 Pages
-
PSE NO 16
6 Pages
-
PSE EX 22
5 Pages
-
PSE NO 27
6 Pages
-
PSE NO 24
6 Pages
-
PSE NO 22
8 Pages
-
PSE IV 16
6 Pages
-
PSE HI 22
6 Pages
-
PSE NO 30
7 Pages
-
PSE M22 IV
7 Pages
-
MCS ES 18
3 Pages
-
MCS ES 22
3 Pages
-
6051.2094
3 Pages
-
6051.2093
3 Pages
-
6051.2078
3 Pages
-
6051.2077
3 Pages
-
6051.2070
3 Pages
-
6051.2072
3 Pages
-
6051.2071
3 Pages
-
6051.2037
2 Pages
-
6051.2030
3 Pages
-
6051.2032
3 Pages
-
6051.2031
3 Pages
-
6051.2027
3 Pages
-
3-107-570
2 Pages
-
3-107-569
2 Pages
-
VAC13KS
4 Pages
-
DD21
5 Pages
-
DD11
5 Pages
-
DF11
6 Pages
-
DG11
7 Pages
-
typ_6051.2016
3 Pages
-
typ_6051.2008
3 Pages
-
typ_6051.2009
3 Pages
-
typ_6051.2001
4 Pages
-
typ_6051.2007
3 Pages
-
typ_6051.2003
3 Pages
-
typ_6051.2004
3 Pages
-
typ_4762
3 Pages
-
typ_3-101-514
3 Pages
-
typ_3-101-501
3 Pages
-
typ_3-100-528
3 Pages
-
typ_3-100-734
3 Pages
-
typ_3-100-526
3 Pages
-
typ_3-100-523
3 Pages
-
typ_3-100-524
3 Pages
-
typ_3-100-527
3 Pages
-
typ_3-100-522
3 Pages
-
typ_3-100-356
3 Pages
-
typ_3-100-355
3 Pages
-
typ_3-100-354
3 Pages
-
Application Note Surge
2 Pages
-
White Paper IP Protection
2 Pages
-
SWA2
2 Pages
-
PB 1021
2 Pages
-
TM12-111
6 Pages
-
PTS
4 Pages
-
Piezo Keypads
4 Pages
-
PB 1011
2 Pages
-
FMAD CEE
3 Pages
-
White Paper Data Center
4 Pages
-
White Paper SPICE library
4 Pages
-
White Paper Cord retention
4 Pages
-
SCHURTER and ESA cooperation
2 Pages
-
Efficient EMC Solutions
8 Pages
Archived catalogs
-
Product News
4 Pages
-
SCHURTER Company Profile
10 Pages
-
PFDF
3 Pages
-
PFHT
3 Pages
-
PFUF
3 Pages
-
SCHURTER Renewable Energies
6 Pages
-
SCHURTER Product News
4 Pages
-
DKFP
5 Pages
-
FMAD RAIL
3 Pages
-
FMAC RAIL
3 Pages
-
FMBD NEO
6 Pages
-
FMAC SINE DCL
4 Pages
-
FMAC SINE
4 Pages
-
FMAB RAIL
3 Pages
-
FMBB NEO
11 Pages
-
FMBB RAIL
3 Pages
-
5120
10 Pages
-
SMD-FTT
1 Pages
-
OMZ 125
1 Pages
-
4840.2200
2 Pages
-
6051.5003
2 Pages
-
6000.0224
2 Pages
-
6051.2030
2 Pages
-
6051.2003
2 Pages
-
FLBB
2 Pages
-
4741
2 Pages
-
P685
2 Pages
-
KE
4 Pages
-
GSF2
4 Pages
-
GSF1
5 Pages
-
Felcom 64
4 Pages
-
6135
5 Pages
-
KG-Bowdencable
4 Pages
-
KD-Bowdencable
4 Pages
-
DC21
3 Pages
-
1074
4 Pages
-
DC11
5 Pages
-
CMF3, CMF6
2 Pages
-
PFNF
3 Pages
-
ESO 10.3x38
1 Pages
-
SHT 6.3x32
1 Pages
-
Product Overview Switches
2 Pages
-
KEB2
1 Pages
-
New product: 6610
3 Pages
-
New product: UMZ 250
3 Pages
-
New product: CSO
2 Pages
-
New product: UST 1206
2 Pages
-
New product: UMF 250
3 Pages
-
New product: UMT-H
3 Pages
-
TA35 Rocker 2Pol
8 Pages
-
SCHURTER range at a glance
236 Pages
-
ASO / FSO
8 Pages
-
Flyer UMT 250 / UMZ 250
8 Pages
-
SCHURTER - Flyer MSM CS
2 Pages
-
Varistors
40 Pages
-
Flyer MGA-S
6 Pages