26.3
Power Breakers, Contactors and Fuses
Fuses General
26
Contents
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Fuses General
Description
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Product Overview
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Power Fuse
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Power vs. Distribution
Eaton’s roots in the
medium voltage power
fuse business began
over 75 years ago under
Westinghouse® Electric.
In 1935, Westinghouse
introduced the medium
voltage boric acid expulsion
fuse followed by the medium
voltage current limiting fuse.
Even today, medium voltage
fuses continue to use that
core technology. Eaton
continues to build on the
technology legacy by
engineering higher
performance, cost-effective
power fuse products.
Eaton’s medium voltage
fuses are manufactured and
tested to the requirements
of the C37-4X series of
standards, which are
maintained and updated
regularly to maintain currency
with industry practices.
These standards are:
IEEE Std. C37.40 ™
IEEE Standard Service
Conditions and Definitions
for High Voltage Fuses,
Distribution Enclosed SinglePole Air Switches, Fuse
Disconnecting Switches,
and Accessories (ANSI).
IEEE Std. C37.41 ™
IEEE Standard Design
Tests for High-Voltage
(>1000V) Fuses, Fuse and
Disconnecting Cutouts,
Distribution Enclosed SinglePole Air Switches, Fuse
Disconnecting Switches, and
Fuse Links and Accessories
used with These Devices
(ANSI).
ANSI C37.42 ™
IEEE Standard Specifications
for High-Voltage (>1000V)
Expulsion-Type DistributionClass Fuses, Fuse and
Disconnecting Cutouts,
Fuse Disconnecting
Switches, and Fuse Links,
and Accessories used with
These Devices (ANSI).
ANSI C37.46
American National Standard
for High Voltage Expulsion
and Current Limiting Type
Power Class Fuses and Fuse
Disconnecting Switches.
The following IEEE standards
are also applicable to the fuse
products covered in this
publication:
IEEE Std. C37.48 ™
IEEE Guide for the
Application, Operation, and
Maintenance of High Voltage
Fuses, Distribution Enclosed
Single-Pole Air Switches,
Fuse Disconnecting
Switches, and Accessories
(ANSI).
IEEE Std. C37.48.1 ™
IEEE Guide for the
Classification, Application,
and Coordination of CurrentLimiting Fuses with Rated
Voltages 1–38 kV.
A better understanding of
some fuse terminology will
help you understand and
select the correct fuse. The
following is a brief overview
of those terms.
ANSI C37.47
American National Standard
for High Voltage Current
Limiting Type Distribution
Class Fuses and Fuse
Disconnecting Switches.
The differentiation is intended
to indicate the test conditions
and where fuses are normally
applied on an electrical
system, based on specific
requirements for generating
sources, substations and
distribution lines. Each
class has its own unique
set of voltage, current and
construction requirements
(see C37.42, .46 and .47).
Low vs. Medium vs.
High Voltage
While fuses are defined in
the ANSI standards as either
low or high voltage, Eaton
has elected to name their
fuses to correspond with the
equipment in which they are
installed. Therefore, per ANSI
C84, our fuses are named
as follows:
●
●
●
Low voltage—1000V and
below
Medium voltage—greater
than 1000 to 69,000V
High voltage—greater than
69,000V
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Power Breakers, Contactors and Fuses
Fuses General
Expulsion vs. Current Limiting (Definitions per ANSI C47.40-1993)
An expulsion fuse is a vented
fuse in which the expulsion
effect of the gases produced
by internal arcing, either
alone or aided by other
mechanisms, results in
current interruption.
Backup Fuses
A fuse capable of interrupting
all currents from the
maximum rated interrupting
current down to the rated
minimum interrupting current.
An expulsion fuse is not
current limiting and as a
result limits the duration of a
fault on the electrical system,
not the magnitude.
Backup fuses are always
used in a series with another
interrupting device capable of
interrupting currents below
the fuse’s minimum
interrupting current.
A current limiting fuse is a
fuse that, when its current
responsive element is melted
by a current within the fuse’s
specified current limiting
range, abruptly introduces
a high resistance to reduce
current magnitude and
duration, resulting in
subsequent current
interruption. Refer to Fuse
Types Protection Range
figure on Page V4-T26-632
for a features comparison.
Fuse Types
There are three current
limiting fuse types: Backup,
General Purpose and Full
Range. It is important that the
user have an understanding
of these definitions to ensure
proper application of the fuse
(see Fuse Types Protection
Range figure on Page
V4-T26-632).
General Purpose Fuses
A fuse capable of interrupting
all currents from the rated
interrupting current down
to the current that causes
melting of the fusible element
in no less than one hour.
General Purpose fuses are
typically used to protect
feeders and components
such as transformers.
Full Range Fuses
A fuse capable of interrupting
all currents from the rated
interrupting current down
to the minimum continuous
current that causes melting
of the fusible element,
with the fuse applied at
the maximum ambient
temperature specified by
the manufacturer.
26.3
General Fuse Component Terms
Fuse Refill Unit (of an
Expulsion Fuse)
A fuse refill unit is a
replaceable assembly
containing the calibrated
current-responsive fuse
element and certain other
items that facilitate current
interruption. On its own, the
refill unit has no interrupting
ability. A refill unit must be
mounted in a fuseholder with
a spring assembly to form a
refillable fuse unit. The refill
unit is the section of the fuse
that must be replaced after a
fuse operation.
Fuseholder (of an
Expulsion Fuse)
A fuseholder is a reusable
holder that when equipped
with a fuse refill unit forms
a fuse unit, capable of
interrupting an overload or
fault current. A fuseholder
is supplied with a spring and
shunt assembly, necessary
to complete the internal
interrupting assembly. The
spring and shunt assembly is
supplied with the fuseholder
but is also available as a
replacement part, as it may
need replacement after
several of heavy operations.
Fuse Unit
A fuse unit is a replaceable
unit or assembly that is
able, on its own, to perform
current interruption. In
the case of a refillable fuse
unit, the refill unit must
be replaced after a fuse
operation. Where a complete
fuse unit is supplied from the
factory, the complete fuse
unit must be replaced after a
fuse operation. All currentlimiting fuses are fuse units.
26
Exhaust Control Device
When expulsion fuses are
used in enclosures, exhaust
control devices (filters,
condensers or mufflers) are
used to control the sound
of the fuse operation, and
to de-ionize and absorb the
fuse exhaust products. These
devices are normally supplied
separately, because of
different characteristics and
ratings. They are reusable but
may need replacement after
several heavy operations.
Mounting
A mounting provides all the
necessary parts to safely
mount a fuse in its intended
piece of equipment. The
base is the metal support to
which all other pieces attach.
Insulators attach to the base
and insulate the live fuse unit
from the base and everything
beyond the base. Live parts
are the parts of the mounting
that are energized once
electricity is flowing. The live
parts provide the means to
hold the fuse unit in place,
electrical contact, and a
place to make line and load
connections.
Non-Disconnect Mounting
A non-disconnect mounting
does not provide a means for
removing the fuse unit until
the circuit is dead and the
fuse unit can be removed
manually. The fuse unit is
held in place by friction
through the use of fuse
clips or by a cross bar.
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Power Breakers, Contactors and Fuses
Fuses General
Disconnect Mounting
The disconnect mounting
allows the fuse unit to be
removed (off load) using an
insulated hook stick. The
hookstick grabs a pull ring
and disconnects the fuse
unit, which may then be
lifted out of its mounting.
Dropout Mounting
Dropout mountings are
used in outdoor applications.
The fuse unit is equipped
with a mechanical trigger that
unlatches the upper contact,
allowing the fuse unit to drop
out, increasing the dielectric
separation, and providing
visible indication of a
blown fuse.
Live Parts
Live parts were briefly
discussed as part of the
“Mounting” definition.
Everything above the
insulators on the mounting
excluding the fuse unit, fuse
holder, and the fuse end
fittings (if required) are
considered the live parts. Fuse
end fittings are discussed
next and are not required
with non-disconnect live
parts, but are required and
included with disconnect live
parts. Live parts may be sold
separately as replacement
parts or for new OEM
applications.
End Fittings
End fittings are metal parts
that attach to each end of a
fuse unit’s ferrules (end caps).
As previously mentioned,
they are used solely with
disconnect fuse applications
or when converting a nondisconnect to a disconnect
fuse configuration.
When end fittings are
ordered, a fitting for each end
of the fuse is included. Keep
in mind that end fittings can
become damaged in use and,
therefore, are sold separately
from the live parts when
necessary. It is not necessary
to purchase an entire set of
live parts when only the end
fittings are required.
General High Voltage Fuse Comparison
Expulsion
Current Limiting
Vented
Sealed
Electromechanical
Static
Interrupts at current zero
Limits fault current
Generally higher voltage and current application
capabilities
Generally higher interrupting ratings
Different time/current characteristics
Different time/current characteristics
Fuse Types Protection Range
Current Limiting Type
26.3
BACKUP
GENERAL PURPOSE
FULLL RANGE
i
i hr.
i min.
i max.
Interrupting Current
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V4-T26-632
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For Immediate Delivery or Tech Support call KMParts.com at (866) 595-9616
Index
A
ability, 2
able, 2
above, 3
abruptly, 2
absorb, 2
Accessories, 1
acid, 1
after, 2
ago, 1
aided, 2
Air, 1
All, 2
all, 2
allowing, 3
allows, 3
alone, 2
also, 1-2
always, 2
ambient, 2
American, 1
An, 2
an, 1-3
and, 1-3
another, 2
ANSI, 1-2
applicable, 1
Application, 1
application, 2-3
applications, 3
applied, 1-2
April, 1-3
arcing, 2
are, 1-3
As, 3
as, 1-3
assembly, 2
at, 1-3
attach, 2-3
available, 2
B
BACKUP, 3
Backup, 2
bar, 2
base, 2
based, 1
be, 2-3
because, 2
become, 3
began, 1
below, 1-2
better, 1
beyond, 2
blown, 3
boric, 1
Breakers, 1-3
brief, 1
briefly, 3
build, 1
Index
business, 1
but, 2-3
by, 1-2
C
CA, 1-3
calibrated, 2
call, 1-3
can, 2-3
capabilitieslifted, 3
capable, 2
caps, 3
case, 2
causes, 2
certain, 2
characteristics, 2-3
Circuit, 1-3
circuit, 2
Class, 1
class, 1
Classification, 1
clips, 2
com, 1-3
comparison, 2
ComparisonThe, 3
complete, 2
Component, 2
components, 2
condensers, 2
Conditions, 1
conditions, 1
configuration, 3
connections, 2
considered, 3
construction, 1
contact, 2-3
Contactors, 1-3
containing, 2
Contents, 1
continue, 1
continues, 1
continuous, 2
Control, 2
control, 2
converting, 3
Coordination, 1
core, 1
correct, 1
correspond, 1
cost, 1
covered, 1
cross, 2
currency, 1
Current, 1-3
current, 1-3
Currentfittings, 3
currents, 2
Cutouts, 1
D
damaged, 3
de, 2
dead, 2
defined, 1
definition, 3
Definitions, 1-2
definitions, 2
Delivery, 1-3
Description, 1
Design, 1
Device, 2
device, 2
Devices, 1
devices, 2
dielectric, 3
Different, 3
different, 2
differentiation, 1
Disconnect, 2-3
disconnect, 2-3
Disconnecting, 1
disconnects, 3
discussed, 3
Distribution, 1
distribution, 1
does, 2
down, 2
drop, 3
Dropout, 3
duration, 2
Index
E
Each, 1
each, 3
Eaton, 1
eaton, 1-3
effect, 2
effective, 1
either, 1-2
elected, 1
Electric, 1
electrical, 1-2
electricity, 2
Electromechanical, 3
element, 2
Enclosed, 1
enclosures, 2
End, 3
end, 3
energized, 2
ensure, 2
entire, 3
equipment, 1-2
equipped, 2-3
Even, 1
Everything, 3
everything, 2
excluding, 3
Exhaust, 2
exhaust, 2
Expulsion, 1-3
expulsion, 1-2
flowing, 2
followed, 1
following, 1
follows, 1
For, 1-3
for, 1-3
form, 2
forms, 2
friction, 2
from, 2-3
FULL, 3
Full, 2
Fuse, 1-3
fuse, 1-3
Fuseholder, 2
fuseholder, 2
Fuses, 1-3
fuses, 1-2
fusible, 2
G
gases, 2
GENERAL, 3
General, 1-3
Generally, 3
generating, 1
grabs, 3
greater, 1
Guide, 1
F
H
facilitate, 2
factory, 2
fault, 2-3
features, 2
feeders, 2
ferrules, 3
figure, 2
filters, 2
fitting, 3
Fittings, 3
fittings, 3
has, 1-2
have, 2
heavy, 2
held, 2
help, 1
High, 1, 3
high, 1-2
higher, 1, 3
hold, 2
holder, 2-3
hook, 3
Index
hookstick, 3
hour, 2
hr, 3
I
IEEE, 1
if, 3
Immediate, 1-3
important, 2
In, 1-2
in, 1-3
included, 3
increasing, 3
indicate, 1
indication, 3
industry, 1
installed, 1
insulate, 2
insulated, 3
Insulators, 2
insulators, 3
intended, 1-2
internal, 2
Interrupting, 3
interrupting, 2-3
interruption, 2
Interrupts, 3
introduced, 1
introduces, 2
ionize, 2
is, 1-3
It, 2-3
it, 2
items, 2
its, 1-3
K
Keep, 3
KMParts, 1-3
kV, 1
L
legacy, 1
less, 2
Limiting, 1-3
limiting, 1-2
Limits, 3
limits, 2
line, 2
lines, 1
Links, 1
Live, 2-3
live, 2-3
load, 2-3
Low, 1
low, 1
M
magnitude, 2
maintain, 1
maintained, 1
Maintenance, 1
make, 2
manually, 2
manufactured, 1
manufacturer, 2
max, 3
maximum, 2
may, 2-3
means, 2
mechanical, 3
mechanisms, 2
Medium, 1
medium, 1
melted, 2
melting, 2
mentioned, 3
metal, 2-3
min, 3
mind, 3
minimum, 2
mount, 2
mounted, 2
Mounting, 2-3
mounting, 2-3
Index
mountings, 3
mufflers, 2
must, 2
N
name, 1
named, 1
National, 1
necessary, 2-3
need, 2
new, 3
next, 3
no, 2
Non, 2
non, 2-3
normally, 1-2
not, 2-3
O
OEM, 3
of, 1-3
off, 3
On, 2
on, 1-3
once, 2
one, 2
only, 3
Operation, 1
operation, 2
operations, 2
or, 1-3
ordered, 3
other, 2
our, 1
out, 3
outdoor, 3
over, 1
overload, 2
Overview, 1
overview, 1
own, 1-2
P
Page, 2
part, 2-3
Parts, 3
parts, 2-3
per, 1-2
perform, 2
performance, 1
piece, 2
pieces, 2
place, 2
Pole, 1
Power, 1-3
power, 1
practices, 1
previously, 3
produced, 2
Product, 1
products, 1-2
proper, 2
protect, 2
Protection, 1-3
provide, 2
provides, 2
providing, 3
publication, 1
pull, 3
purchase, 3
Purpose, 2
PURPOSELive, 3
R
RANGE, 3
Range, 2
range, 2
Rangeused, 3
Rated, 1
rated, 2
ratings, 2
ratingsunit, 3
reduce, 2
Refer, 2
Refill, 2
refill, 2
Index
refillable, 2
regularly, 1
removed, 2-3
removing, 2
replaceable, 2
replaced, 2
replacement, 2-3
required, 3
requirements, 1
resistance, 2
responsive, 2
result, 2
resulting, 2
results, 2
reusable, 2
ring, 3
roots, 1
S
safely, 2
Sealed, 3
section, 2
see, 1-2
select, 1
separately, 2-3
separation, 3
series, 1-2
Service, 1
set, 1, 3
several, 2
shunt, 2
Single, 1
sold, 3
solely, 3
some, 1
sound, 2
sources, 1
specific, 1
Specifications, 1
specified, 2
spring, 2
Standard, 1
standards, 1
Static, 3
Std, 1
stick, 3
subsequent, 2
substations, 1
such, 2
supplied, 2
Support, 1-3
support, 2
Switches, 1
system, 1-2
T
Tech, 1-3
technology, 1
temperature, 2
terminology, 1
Terms, 2
terms, 1
test, 1
tested, 1
Tests, 1
than, 1-2
that, 1-3
The, 1-3
the, 1-3
their, 1
then, 3
There, 2
Therefore, 1
therefore, 3
These, 1-2
these, 2
They, 2
they, 1, 3
this, 1
those, 1
three, 2
through, 2
time, 3
to, 1-3
today, 1
transformers, 2
trigger, 3
Type, 1, 3
Types, 2-3
types, 2
typically, 2
Index
U
under, 1
understand, 1
understanding, 1-2
unique, 1
Unit, 2
unit, 2-3
units, 2
unlatches, 3
until, 2
updated, 1
upper, 3
use, 1-3
used, 1-3
user, 2
using, 3
with, 1-3
within, 2
www, 1-3
Y
years, 1
you, 1
Z
zero, 3
V
Vented, 3
vented, 2
visible, 3
Voltage, 1, 3
voltage, 1, 3
Voltageengineering, 1
Voltages, 1
Volume, 1-3
vs, 1-2
W
were, 3
Westinghouse, 1
When, 2-3
when, 2-3
Where, 2
where, 1
which, 1-3
While, 1
will, 1