curva
DESCRIPTION
Curvas de fusibles de potencia.TRANSCRIPT
.7
.5
.02
.01
.4
.2
.04
.03
.3
.05
.1
.07
.06
.08
.09
.8
.91
.6
7
5
4
2
3
89
10
6
20
80
60
50
30
40
90100
70
200
800
600
500
300
400
9001000
700
5 6 7 8 9 10 20 30 8070605040 4000
90 6000
90 0
0010
0 00
0
7000
9000
70 0
00
80 0
00
8000
60 0
00
10 0
00
40 0
00
50 0
00
30 0
00
20 0
00
3000
2000
1000
5000
400
600
700
900
800
300
200
100
500
5 6 7 8 9 10 20 30 8070605040
400090
6000
90 0
0010
0 00
0
7000
9000
70 0
00
80 0
00
8000
60 0
00
10 0
00
40 0
00
50 0
00
30 0
00
20 0
00
3000
2000
1000
5000400
600
700
900
800
300
200
100
500
CURRENT IN AMPERES
CURRENT IN AMPERES
TIM
E I
N S
EC
ON
DS
TIM
E IN
SE
CO
ND
S
.7
.5
.02
.01
.4
.2
.04
.03
.3
.05
.1
.07
.06
.08
.09
.8
.91
.6
7
5
4
2
3
8910
6
20
80
60
50
30
40
90100
70
200
800
600
500
300
400
9001000
700
TCC Number 153-2July 14, 2015© S&C Electric Company 1972-2015, all rights reserved
BASIS—These fuse units are tested in accordance with the procedures described in ANSI Standard C37.411981, and they are rated to comply with ANSI Standard C37.461981. As required by these standards, the minimum melting current is not less than 200% of fuseunit ampere rating, and the minimum melting curves are based on tests starting with the fuse unit at an ambient temperature of 25°C and no initial load.
CONSTRUCTION—Fusible elements for fuse units rated 3E through 7E amperes are nickelchrome, under controlled tension; fusible ele ments for fuse units rated 10E through 400E amperes are silver, helically coiled. All are of solderless construction.
TOLERANCES—Curves are plotted to minimum test points. Maximum varia tions expressed in current values are:
Plus 10% for 10E through 400E ampere ratings.Plus 15% for 5E through 7E ampere ratings.Plus 20% for 3E ampere rating.
APPLICATION—Like all highvoltage fuses, these fuse units are intended to accommodate overloads, not to interrupt them. Accordingly, they feature fusible elements which are designed with a min imum melting current of 200% of the fuseunit ampere rating (for fuse units rated 100 amperes or less) or 240% of the fuseunit ampere rating (for fuse units rated over 100 amperes). As a result, these fuse units have considerable peakload capabilities; however, they should never be exposed to loading in excess of the peakload capabilities listed in S&C Data Bulletin 240190.
Since fuse units having nickelchrome or silver element construction are not subject to damage by aging or transient overcur rents, it is unnecessary to replace unblown fuse units of either of these constructions in singlephase or threephase installations when one or more fuse units have blown.
COORDINATION—Any preloading reduces melting time. While this phenomenon especially pronounced in other makes of fuses having minimum melting currents appreciably less then 200% of rating, the effect of preloading must nonetheless be determined for the S&C fuse units represented by these curves (see S&C Data Bulletin 240195) and adjustments to these curves must be made:1. When close coordination is required;2. When, regardless of the preciseness of coordination, the fuse unit
is subjected to temporary overloads.
There are cases where the coordination requirements may be very exacting, for example, in coordinating a transformer primary fuse with a secondary breaker and a sourceside breaker. The time interval between the operating characteristics of the two breakers may be very narrow. Under these circumstances there must be an extremely short time interval between the minimum melting and the total clearing characteristics of the fuse.
The fuse units represented by these curves possess this short time interval feature, since—having a nondamageable fusible ele ment of precise construction—they require:1. As little as 10% total tolerance in melting current—compared to
the 20% tolerance of many fuses (20% and 40% respectively in terms of time).
2. No “safetyzone” or setback allowances.
This narrow time band normally will provide the desired coordination. If the selected S&C Standard Speed fuse unit does not meet the coordination requirements, check to see if the same ampere rating in the S&C Slow Speed or S&C Very Slow Speed will satisfy.
Sometimes a selected ampere rating will fail to meet the coordination requirements in any available speed. In this case the selection of another ampere rating for either the protecting or protected fuse usually will satisfy all requirements.
Do not assume that other fuses that do not employ S&C’s silver, helically coiled fusible element construction can better resolve a coordination impasse than the use of another ampere rating in one of the S&C speed options. Such other fuses, including “timelag” speeds, “superslow” speeds, and “highsurge” speeds, require the use of “safetyzone” or setback allowances and, in addition, they have larger construction tolerances (plus 20% in current; plus 40% in terms of time). The application of these two factors will give a time interval between the adjusted minimum melting curve and the total clearing curve greater than in the case of S&C speed options.
FUSE UNITS AVAILABLE—Type kV Nom. Ratings Ampere RatingsSMU20® . . . . . . . . . . . . 14.4 through 34.5 . . . . . . 5E through 200ESMU40® . . . . . . . . . . . . . 4.8 through 25 . . . . . . . 3E through 400E
MINIMUM MELTING TIME-CURRENT CHARACTERISTIC CURVES
SMU FUSE UNITS — S&C STANDARD SPEED
7E 10
E
13
E
25
E3
0E
40
E
5E
80
E6
5E
50
E
20
E
15
E
17
5E
15
0E
12
5E
10
0E
20
0E
3E 25
0E
30
0E
40
0E
2-2
50
E
2-4
00
E
2-3
00
E