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How the correct choice of the
residual current device ensures
operator safety, machine uptime
and profitability
Introduction
Technology continues to rapidly
evolve, and machine builders are
faced with designing products to
enable their customers to produce
faster, and more efficiently, at a lower
cost. Product lifecycles are becoming
shorter, placing demands on machine
builders to design and develop highly
customized machines. Exporting
equipment remains complex, as
electrical standards often differ from
country to country.
Manufacturers and their end users are
looking more towards their suppliers
for support, due in part to in-house
engineering team size reductions.
One aspect of this is electrical circuit
protection, which can impact both
safety and machine up-time. Electrical
earth leakage current that can occur,
and design in the appropriate RCD.
Types of protection
Devices have to shield operators
and technicians from the dangers of
electric current, both during normal
use and fault conditions. Potentially
life-threatening accidents can result
from either direct or indirect contact.
Direct contact refers to when a person
touches a live electrical part that is
intended to be live during normal
operation. Indirect contact is a fault
when a conductive, non-live exposed
and touchable part becomes live due
to an electrical fault.
There are multiple types of protection
required; basic, fault, additional and
fire. Basic prevents contact with live
parts through insulation or a cover.
Fault protection includes situations
where an insulator (basic protection)
fails and the RCD switches off before
dangerous voltages can occur on
Protecting man and machine against damaging residual currents
Peter-Lukas Genowitz, Eaton
faults can have devastating effects on
the human body causing injury, and
lead to machine failure and fire –
affecting productivity.
The function of a residual
current device
Residual currents in electrical systems
are caused by either fault conditions
or generated by system components
such as frequency converters. The
role of a residual current device (RCD)
is to automatically disconnect the
power supply if the fault can pose a
risk.
Residual currents can arise for many
reasons and take many forms. The
biggest challenge is being able to
differentiate between all the possible
forms of residual current, while
protecting people and equipment, but
on the other hand avoiding nuisance
tripping related to system caused
earth leakage currents. The solution
is to recognise the different forms of
Sensors
Special Edition
58 l New-Tech Magazine Europe