Automation Canada - Industrial Automation - 11

tested. The only option for fuses is to replace them on an interval
schedule before they blow. Otherwise, there's the risk of a nuisance
tripping situation that could lead to production loss.
Worker Safety
Replacing fuses requires the door of the panel to be open. This
creates a situation where potential live voltage contact is possible.
Some industrial users require personnel to wear an arc fault suit to work
on live panels. Arc flash accidents are not uncommon - and they can be
deadly.
To make the situation worse, some fuse clips and fuses are completely
accessible from the front. Special covers need to be added to prevent a
live power hazard. Aſter service, the maintenance team needs to be
attentive and assure the cover is properly re-installed.
What's more, replacing a power fuse requires a trained electrician,
which can delay production until one can arrive on site. Some fuse
blocks require a fuse puller or a special tool for servicing, which aren't
usually provided or readily available. This can lead to a potentially
dangerous situation if someone attempts to remove a fuse with an
incorrect tool like a metal screwdriver.
Another issue is the level of global support available. When replacing
a fuse, the replacement parts commonly found in North America might
not be as accessible in Europe. Many OEMs prefer to standardize
products to ensure components have global support.
With breakers, it's easier to select components that will be universally
available and supported in different markets.
Overall costs
The overall cost of a breaker is lower than a fuse, when fuses' life-cycle
costs are factored into the equation. Between the time lost to replace
fuses when short-circuits happen, fuse replacement costs, and the
extended time required to diagnose problems, the overall costs of fuses
add up quickly.
It's also important to consider the risks that maintenance employees
are exposed to when replacing fuses.
In some situations, breakers are the same price as fuses, plus the fuse
CANADIAN AUTOMATION
* Simple with breakers, many types and fits with fuses
** Little or none with breakers, spares and types with fuses
*** Breakers have long mechanical and electrical life
The right applications for breakers and fuses
Fuses can be useful in circuits that need a high interrupting capacity or
for sensitive electronic equipment that requires extra fast-acting
protection. However, for most UL508 control panels and MCCs,
breakers are a better solution. The benefits outweigh the initial
investment, especially when downtime is particularly expensive.
There are increasingly more DC circuits in today's modern panels,
with the growing acceptance of alternative energy and the EV market.
There's also a trend toward changing 120vac controls circuit to 24 VDC
for safety reasons, in case of accidental contact with live voltage.
Breaker technology has improved and is now capable of handling DC
circuits.
VOLUME 4, ISSUE 1
11
holder and disconnect switch required to make a complete system.
With all these factors considered, fuses are an expensive proposition.
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