About Fusetek FUSETEK is a 100% family owned

About Fusetek
FUSETEK is a 100% family owned Canadian company and we have been serving the Canadian electrical
industry and
it’s customers for over 37 years.
Originally, under the name of Tekelek-Dorman Smith, we brought the first dual CSA/IEC approved fuses
to the
Canadian market. We have done much pioneering work that has since become an accepted standard
with equipment builders and users alike.
Today, Fusetek is partnered with Littelfuse, SIBA and GEC and together we offer the most
comprehensive range of
fuse products available in North America.
Our services run from co-ordination studies to fuse surveys to fuse seminars. We can custom design and
manufacture
fuses for a specific application or source an oddball fuse from anywhere in the world.
With distributors and agents from coast to coast, we can quickly respond to our customers’ needs.
No matter what aspect of fusing you’re involved with - Fusetek can be of service.
About Fusesoft On-Line
Over the years, Fusetek has provided many fuse seminars across the country in an effort to educate
customers about
fuses and fuse application. Always, we have stressed product understanding before product specification.
This software is a natural extension of what we have been ‘preaching’ for the last 35 years. The fact that
there has been much talk and debate over correct fuse protection for control (and IEC control in
particular) and more recently a resurgence in fuse interest due to Arc Flash considerations only
underscores the importance of correct fuse application.
Until now there has been no economical and easy way to portray the interaction of the various circuit
components that come into play in today’s electrical systems. FUSESOFT simplifies the selection of fuses
over a broad range of applications. It contains many more device choices, and where the original
Fusesoft was table driven, our new Fusesoft On-Line determines fuse choice by comparing curves and
zones, so the variables can be infinitely changed and Fusesoft On-Line will keep up with inputs.
Whether Fusesoft On-Line is used to select proper fuse size for a project or mill application, or used as an
education tool, there has never been a clearer, easier way to understand fuse application.
As everything these days, Fusesoft On-Line is evolving to meet the requirements if our customers and
markets. If you notice any errors, or have suggestions to make it better, we’d appreciate hearing from
you.
E mail
Toll free tel.
Toll free fax
[email protected]
(800) 479-3875
(800) 866-7690
Fusesoft On-Line - General information
Fusesoft On-Line will run in any of today’s popular browsers such as Internet Explorer or Mozilla Firefox.
You may save Fusesoft On-Line as a bookmark as you would any other website.
Screen resolution
Fusesoft On-Line was designed to run with a screen resolution of 1280 x 800 or greater. Although
Fusesoft On-Line will start and run at lower screen resolutions, some screen elements may be misaligned
or off screen - requiring scrolling to see them all.
Starting Fusesoft On-Line
When you first start Fusesoft On-Line, you will be taken
to the home screen.
The home screen has the Help icon
with the
Module and home page icons are arranged along the
bottom. Click on the module of your choice. To return to
the home screen, click on the ‘Home Page’ icon. The
module toolbar will remain at the screen bottom in all
the modules.
When a module is first started, you
will be presented with essentially a
blank screen.
When a module is first started,
most of the input fields will be
blank, as will the main graph area.
Input
parameter
area
Graph Area
As you enter the basic circuit
parameters into the input area, the
graph will be generated showing
your selections. Navigate from
field to field by clicking or tabbing
to the new fields.
Once the fuse type is selected,
Fusesoft On-Line will select and
draw the appropriate fuse curve.
This icon will draw your attention to hints or warnings.
File saving and printing
Print an application by selecting ‘Print’ from your browser’s toolbar. To save your application, click on the
‘Save to PDF’ button and specify the folder to save the file in. Your application can also be printed from
this PDF file once downloaded.
Before starting a new application, click the ‘Reset Form’ button to clear the data. Failure to do so may
result in inaccurate results, or delays in redrawing the screen elements.
Help File
On-screen help is available by clicking on the
be printed out to serve as a handy reference.
icon on the Home page. This manual can also
Motor Application Module Click on the Motor Application icon
This module selects appropriate fuse ratings for full voltage across-the-line motor starting applications.
See note at
The end of chapter re: reduced voltage starting applications.
When the module in first started, the fields will be blank as will the chart area. As you select data from the
drop down fields, the graph will start to fill in.
Default full load and starting currents are supplied by the program. You may alter these default values to
match actual known values if different from those supplied.
Small differences between your actual values and those supplied by the program will not have any
impact on fuse sizing. Similarly, slight difference is system voltage (eg: 600V vs. 575V ) will not affect the
fuse sizing.
Continue down the input fields entering or selecting data.
System voltage: select from the available drop down choices.
1 or 3 phase. In most cases, this will be pre-selected for you.
Motor HP (if 600V or less)

Run-up time. (the default is 8s.)
Overload relay mfr./type
Fuse I type. Select the type of fuse to use.
Fuse II type. Select the 2
nd
fuse type.(optional)
Memo field (comments will be saved or printed with file)

Reset and File save buttons
Once the basic circuit data is input, Fusesoft On-line will draw the graph.
After the first fuse type is selected, Fusesoft On-Line will auto-select a fuse rating based on your inputs
and draw the fuse’s time current curve on screen. You may override the recommended rating by selecting
a different amp from the ‘Fuse Amp Rating’ dropdown box. The screen will re-draw to show your new
choice. Use this function to do what-if scenarios or duplicate a field condition.
A second fuse type may be selected. In this way, it is possible to choose alternate fuse types and ratings
for comparison with the first fuse type. The auto select feature and manual overrides function as for the
st
1 fuse choice.
Once you have completed an application, you can save it as a PDF by clicking the ‘Save to PDF button,
print it using your browser’s print command, or clear the form and start another application.
or clear the form by clicking on the Reset Form button.
Click the ‘Reset Form’ button to clear all the variables from memory. Failure to do so may result in
slow screen re-draws.
What is Coordination?
Coordination is the process of selecting protective devices to interact in the best way possible to protect
the control
equipment. In the motor starting circuit, the motor, the overload relays and the fuse all interact with each
other to
provide running (overload) protection for the motor and over current (short circuit) protection for the motor
control.
Ideal motor/fuse/overload co-ordination is achieved when the fuse is selected such that the motor can
operate
throughout its normal range of running/starting currents without overload or fuse operation. The overload
relay can
operate under all normal conditions without nuisance fuse operation, but the fuse will still operate quickly
on levels of
current that would otherwise damage the control.
Fusesoft On-Line uses the following protection parameters:
1. The overload relay must operate before the fuse on
locked rotor currents and less. The fuse must not be
damaged during this process.
A fuse that operates at the same time as the overload
makes the overload redundant. Overload relays are
designed to provide close running overload protection for
motors – a function that fuses are not designed for.
Fuses cannot provide the same close overload
protection, so resist the urge to undersize your fuses
thinking you are getting better motor protection.
The motor must start and run up to speed without fuse
operation or damage. This seems obvious but many fuse
outages occur simply because the fuse is too small.
2. The fuse must operate before the overload relay on
currents approximately 10-12 times motor full load amps
and greater. This is to protect the control components
from excessive interrupting duty. These parameters give
us a "coordination window" bounded by the;




Overload relay cold trip (light blue)
Overload relay hot trip (light red)
Motor Locked rotor (green)
Damage point of control (Yellow)
The fuse curve (dark blue) must pass through this "window" to meet the above requirements. This coordination will offer the optimum combination of motor starting capability and over-current protection. It will
result in less fuse operations (downtime) and enhanced protection for the motor and control gear. Any
fuse whose curve passes through this "window" will give good over-current protection and shows why
fuses should be chosen on the basis of their curve - not their amp rating.
This method of selection will also ensure that you have the smallest practical fuse rating, which will
enhance your overall compliance with Arc Flash requirements.
A suitable fuse choice will be confirmed with a message Fuses too small or large will result in a red warning message.
or
In some applications, Fusesoft On-Line will not be able to find a suitable match and will display a
message similar to;
This can result if the fuse series chosen does not have a high enough rating available, or if the available
choices are too far out of range in either direction (too small or large) to fulfill the program parameters. In
this case, manually select a fuse rating to draw the curve on screen, or choose a different fuse type.
Some common field conditions.
Fuses too small.
Fuse curves that pass to the left of the coordination window risk nuisance blowing during normal motor
starting conditions. These conditions are normal and should be cleared by the motor starter overload
relay/contactor.
In our example on the right, although the 100A
fuse may allow this motor to start, it could be
damaged and operate at a later time. If there are
any variances in motor accelerating time or
starting current, the fuse would blow.
On locked rotor, the fuse will definitely operate in
advance of the overloads relays.
This situation could arise due to;
o
o
o
o
Improper sizing.
Using a fast acting in place of a time
delay fuse
Not wanting to go up to the next switch
or clip size to accommodate the correct
fuse.
Deliberately putting in fuses on the small
size to ‘protect control better’ or to reduce Arc Flash energy
This type of coordination will result in high fuse consumption and excessive downtime as a result.
Generally, if you are constantly blowing fuses for no apparent reason, they are too small for the
application.
Fuses too large
Fuses that are installed too large for an application are a much bigger problem. Because they are so
large, they will not operate as often, lulling the user into thinking everything is okay.
Fuse curves that pass to the right of the
coordination window force the control gear
to operate on current levels beyond their
rated breaking capacity (yellow line). This
situation could arise due to:
o
o
o
o
Indiscriminate use of the 300%
CEC sizing rule.
Replacing a fast acting with a time
delay fuse.
Not wanting to go to a lower switch
or clip size.
Improper sizing
Fuse over sizing will result in more wear
and tear on the contactors and overloads
and in worst case conditions, the control
could fail completely.
If you are going through a lot of
overloads and contactor kits, check to make sure your fuses are not too large.
Some combinations of voltage/motor/fuse type may result in not being able to select a curve that is
ideal. This could be because:
o
Excessive locked rotor currents (particularly on small HP motors) have reduced the
coordination ‘window’ size.
o
European overload relays generally have a lower breaking capacity and so reduce the
coordination window.
o
Fuse curves in lower ratings having large 'gaps' between one rating and the next, making it
harder to find an ideal match.
This is normal. In these instances, you must choose to do one of the following:
o
Choose a fuse curve that passes to the left of the window. This will increase the risk of nuisance
blowing and downtime. This risk is reduced by the fact that most small motors are often up to
speed in less than 5 seconds.
o
Choose a fuse curve that passes to the right of the window. This can put additional stress on the
control components as the takeover point of the fuse has been increased. This risk is reduced by
the fact that the current levels in question are seen infrequently. There are a few combinations
where Fusesoft On-Line may select this option. This is likely because the next lower size would
not allow a motor start.
Standard vs. Heavy Duty applications
The recommendations of this program are based on the following assumptions:





Locked rotor (starting current) of 6X the normal full load amps.
4 evenly spaced starts per hour.
An ambient enclosure temperature of 32*C max.
An accelerating time of 10 seconds max.
If any of your operating parameters exceed the above conditions, it may be necessary to increase your
fuse size. How this affects your coordination can be seen by manually selecting the desired fuse amp
rating.
Reduced Voltage starts
Although this program is for full voltage direct-on-line starting applications, it can also be used for reduced
voltage
starting applications if the actual starting current is known.

Select your motor Voltage and HP rating and accelerating time as you normally would.

Then manually alter the starting current value to match your application. Fusesoft On-Line uses
starting current to calculate fuse sizing, so the program will still select the correct fuse.
Because reduced voltage starters result in lower inrush currents to the motor, it is possible to choose
smaller fuse ratings as a result. Sometimes too small! Fusesoft On-Line will not allow a fuse rating to be
chosen less than 125% of the circuit FLC and will display the following message:
No Damage Protection
The IEC 947.4 is an elaboration of the old Class "C" protection introduced to Canada several years ago.
Both these
specifications aim at providing "no damage" protection limits for control gear.
No damage is defined as: ".. light contactor contact welding easily separable with a screwdriver, and no
permanent alteration of the Overload relay trip curve.."
Fusesoft On-Line identifies the overload relay as the weak link in the combination starter chain and it is
overload withstand that is shown in the co-ordination. The contactor’s withstand will always be greater
that the overload relay's, so fuses that protect the overload will also protect the contactor.
For instance, a 20A contactor may have an overload relay block, or heater installed to protect a small
motor rated at say, 5A. The withstand limit of this small overload is much less than that of the contactor.
Therefore, devices chosen simply to protect the contactor would not provide adequate protection for the
overload relay.
Arc Flash considerations.
Arc Flash is prompting users to re-examine their electrical systems, and in particular, their overcurrent
protection. In the case of fuses, the tendency is to try to reduce the fuse size to as low a rating as
possible to reduce the incident energy during a fault.
It is our view that the fuse rating should be applied as small as practical. A fuse size that is too small for
an application will trade lower Arc Flash energies for increased downtime. This is not a practical solution
in the real world.
In practice, most HRC fuse installations using 600A or smaller fuses will result in a Hazard Risk Category
‘0’ – so there is little to be gained by reducing fuse sizes trying for that nth degree of energy reduction.
Fusesoft On-Line will select the fuses with the optimum balance of motor starting capability and protection
for your control.
In General
o
Class C, Class J, Class RK1 or Class CC fuses will provide ‘Type 2’ do damage protection for
IEC control.
o
For North American NEMA rated components, any HRC fuse will effectively provide "no-damage"
protection.
o
Series rated requirements will also be satisfied by sizing the fuses as recommended.
o
HRC fuses up to 600A provide the lowest Arc Flash Hazard Risk category possible (0).
Incremental reduction of fuse size is counterproductive.
Transformer Application Module Click on the Transformer Application icon.
This module selects the appropriate fuse rating based on user input transformer circuit variables.
When the module in first started, the fields will be blank as will the chart area. As you select data from the
drop down fields, the graph will start to fill in.
Default full load and inrush currents are supplied by the program
o Select transformer type. This makes a difference to the inrush
characteristics
o
o
o
o
Enter system voltage on primary
Select 1 or 3 phase (this is usually preselected for you)
Enter transformer size in kVA
Enter magnetizing inrush factor (12 is default)
o
Select if secondary overcurrent protection is present or not.
o
Choose first fuse type
o
Choose second fuse type and rating (optional)
o
Enter any notes before saving or printing.
o
Reset form and Save buttons
Basic circuit data is calculated from the voltage and Kva inputs. It is not changeable. Selecting whether
the secondary has overload protection or not has no impact on the program’s selection criteria, but will
alter the maximum CEC allowed fuse size as a percentage of the primary FLC. This is only an information
field.
Once you have completed an application, you can print it, save it as a PDF by clicking the ‘Save to PDF
button
or clear the form and restart by clicking on the Reset Form button.
Click the ‘Reset Form’ button to clear all the variables from memory. Failure to do so may result in
slow performance.
Notes on use.
When a transformer is energized, the primary windings draw a surge current while the magnetic flux is
being established. The primary windings are their own load, and this inrush occurs any time the
transformer is energized, regardless of whether the secondary side is loaded or not.
A fuse curve will be selected so that it allows this magnetizing
inrush to pass without fuse operation. This means the fuse
curve must pass to the right of the magnetizing inrush curve by
a suitable margin to allow for tolerances.
For the magnetizing inrush factor field, the program defaults to
the ‘rule of thumb’ 12X FLC inrush. If you know the inrush
characteristics of your transformer, enter a number that is a
multiple of the transformer FLC. Smaller inrush currents allow
smaller fuses to be used.
Fusesoft On-Line will choose a fuse that passes the inrush
point by a minimum of 20% to avoid fuse damage or nuisance
outages and provide a message similar to;
Selections too far out of range will show one of the messages:
or
A second fuse type may be selected for comparative purposes. The auto-size function works the same
way as for the first fuse type. In this way, it is possible to choose different fuse types and for comparison
with the first fuse choice.
In some instances, a fuse selection may seem large relative to the transformer inrush. The smallest fuse
that can be used is 125% of the circuit FLC. This is dictated by our Canadian Electrical code which
imposes a maximum 80% circuit loading (125% of circuit FLC). So even though a fuse’s characteristic
may be capable of energizing the transformer, it still has to meet these CEC minimums. A message will
be shown if a fuse is too small to meet these requirements.
Transformer size is expressed in kVA. Improper entry here will result in incorrect inrush and full load
current values. Examples;
4MVA = 4000
1000kVA = 1000
1000VA = 1
100VA = .1
50VA = .05
Transformer magnetizing inrush defaults are as follows. The inrush factor overwrite field alters the 0.1s
inrush only.
Power Distribution Transformer
Control Transformer
Lighting ballast
0.1 second inrush
12X FLA
12X FLA
12X FLA
0.01 second inrush
20X
25X
40X
Fuses in parallel.
Large transformers may require a larger fuse rating than is available in a single body for a given series. It
is permissible and standard practice to parallel fuses to get these higher amp ratings. Selections are
provided for double and triple barrel arrangements on certain fuse types.
For fuses in parallel, general considerations are;
Interrupting rating
Minimum breaking current
Amp rating
Time current curve
– is the same as for a single barrel of the same series.
- is a multiple of the single barrel m.b.c
- is a multiple of the single barrel rating
- is multiple of single barrel curve ordinates (current)
Capacitor Application Module
Click on the Capacitor Application icon
This module will select a fuse based on the calculated capacitor full load amps and any de-rating factors
selected.


Enter system voltage
Select 1 or 3 phase.(this is normally preselected)

Enter capacitor size in kVAR

Select Yes if your installation meets these

Choose fuse type

Enter any notes or comments before saving or printing

‘Reset Form’ and Save buttons.
When the module is first started the fields and the graph area
will be blank. Once you input voltage and kVAR information,
the graph will generate.
The red line is the damage curve of the capacitor enclosure.
To provide adequate protection against capacitor case
rupture, the fuse curve must lie to left of this curve. This
capacitor damage curve portrayed is an average of several
different mfr’s and types of capacitors. If a suitable fuse
cannot be found for your application, it would be best to
obtain the specific capacitor data from our supplier and give
us a call.
The program will calculate the nominal capacitor FLA and
select a fuse rating based on the input voltage and calculated
capacitor FLA. The initial fuse selection is based on 175% of
capacitor FLA. This factor takes into account the charging
currents of the capacitor it is installed on, as well as variables
such as harmonics, manufacturing tolerances, and over
voltages.
De-Rating considerations.
If capacitors are subjected to repeated switching duties, or are part of a larger capacitor bank, the fuse
size must be increased to allow for the additional charging currents present.
If ‘Yes’ is selected for the ‘Does this installation experience repeated switching….’ Field, the fuse size is
increased by a factor of 1.6X the normal size. This is to ensure that increased heat generated by
repeated switching can be dissipated, and that if healthy capacitors ‘dump’ into failed units, that the fuses
on the healthy capacitors are unaffected.
When assessing the fuse selection, check to ensure that the fuse curve (blue line) lies to the left of the
capacitor damage curve (red line). This will ensure that the capacitor is not subjected to current levels
that could cause case rupture.
Some time delay fuses cannot be selected using this 1.6X factor without touching or crossing the
capacitor rupture curve. In this case, it is best to select a fast acting fuse instead. If a fuse curve touches
or crosses the capacitor damage curve, the following message will be displayed;
If a fuse is chosen that is less than 125% of capacitor FLC – the following message will be shown.
Open Letter to all users of fuses on capacitor circuits.
Over recent years, there have been many questions regarding fuses used on capacitor circuits. The use
of capacitors for power factor correction/power conditioning is increasing daily, and many capacitors use
external HRC fuses to 'protect' the capacitors. The area of fuse/capacitor application is a difficult one due
to the large variations in connection variations, field and circuit conditions, and lack of specialized
knowledge in all these disciplines from any one source.
We are issuing this bulletin to address some of the concerns and application variants. Although this article
is aimed at medium voltage users, the comments still apply to 600V or less circuits. Generally, the
consequences of misapplication on low voltage are not as spectacular as medium voltage….
The Fuse's Role
First, we must understand several aspects of HRC fuses as used on capacitors.

The fuse does not 'protect' the capacitor - but acts as an emergency 'disconnect device' should
the capacitor develop an internal fault, the whole idea being to disconnect the capacitor from the
supply before its case ruptures. The fuse cannot offer any degree of overload protection for the
capacitor due to the necessity of using a high amp rating (relative to the capacitor FLA) to pass
the charging current without nuisance operation.

Most medium voltage fuses are what are termed 'partial range' devices in as much as they are
not capable of reliably interrupting low overcurrents on the order of less than 300-400% of the
fuse rating.

Generally, the short circuit performance of today's current limiting fuses is so good, that the use
of higher fuse ratings still provides excellent protection against capacitor case rupture.
If we consider the above, it is apparent that there is nothing to be gained by fusing too small, and indeed,
putting the fuse in a situation where normal operating transients could cause operation is to be avoided.
With this in mind - it is advisable use larger fuse ratings while still protecting the capacitor against case
rupture. In this manner, the fuse is kept from operating until the capacitor actually develops an internal
fault.
In terms of application on capacitors - the following conditions must be kept in mind.

Proximity of other capacitors. Other capacitors can 'dump' into failed capacitors – causing
premature fuse operation of the fuses on the good capacitors.

Tolerances on capacitors can run as high as 15%, so this overage has to be allowed for.

Harmonics. The higher the harmonic current or frequency - the more heating effect it has on the
fuse, so this must be addressed through de-rating of the fuse (ie: a larger rating)

Repeated switching duty. This creates greater heat buildup in the fuse, so it has to be increased
in size to be able to absorb and dissipate this additional heat.

High ambient temperatures (greater than 32 deg. C) inhibit the fuse's ability to dissipate heat to
surrounding air and may require fuse de-rating (ie: higher rating). Loose connections can also
contribute additional heating into the fuse.

Failure to replace fuses in sets of 3 on 3 phase circuits. Circuit conditions that cause one fuse to
operate, could have damaged other fuses. Unless these fuses are replaced also, they could
operate prematurely or unpredictably at a later date.
In many cases, particularly if any of the above conditions are encountered – it can result in a fuse that is
underrated for the application. This in turn results in nuisance operation at best, or catastrophic failure in
worst case scenarios (particularly in HV circuits).
Program Limitations and Disclaimer
Certain assumptions have had to be made in the interests of simplicity and programming. Program defaults
and assumptions have been discussed in each module.
This program has tried to portray the characteristics of the various devices as accurately as screen
resolution, scaling allows. The device information portrayed is accurate to the best of our knowledge.
However, it is the responsibility of the user to verify the information supplied.
This program is intended as a trouble shooting and education tool. Although the results will be reasonably
accurate, Fusesoft On-Line is not intended to replace or be used in lieu of formal engineering practices.
In the case of Arc Flash, where legal consequences are tied to the Arc Flash certification process, formal
third party assistance should be sought. The information in this module, while reasonably accurate, is not a
substitute for this process.
There may be some conditions that Fusesoft On-Line cannot cater to. In this case, we would encourage
you to contact our offices.
Agents and Dealers
Our products are available across Canada through a comprehensive network of dealers and
representatives. For a complete listing or to find the one nearest you, please visit our website at:
www.fusetek.com
Updates and corrections
Updates will be posted on our website as and when they become available.
Like any new program, there are bound to be errors and omissions that have not been tested for. If you encounter
problems or have any suggestions to improve this program, we’d like to hear from you.
Our E mail is:
[email protected]