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Residual Current Circuit Breaker - RCCB.
This type of circuit breaker works
by comparing
the current going in to an
appliance with
the current coming out.
When an appliance is working correctly
all of the current entering the appliance through the live wire
is returned to the power supply through the neutral wire.
In the picture below the strength of the magnetic
field
is the same in
both coils because they both have the
same current.
If something goes
wrong with the appliance
some of the electric current will flow through the earth wire.
The amount of current flowing through
the neutral wire decreases
and now there is a difference between
the current entering the appliance through the live
wire
and the current returned to the
power supply through the neutral wire.
This difference is called the
residual current.
The coil connected to the neutral wire now has
a weaker
magnetic field
than the
coil connected to the live wire.
The iron rocker turns about the
pivot and the contacts are disconnected
which switches off the appliance and makes it safe.
See the picture below.
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Copyright © 2008 Dr. Colin France. All Rights Reserved.