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Residual Current Circuit Breaker - RCCB.
An RCCB is also called an RCD (Residual Current Device).
How does a Residual Current Circuit Breaker Work?
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.
The RCCB acts to switch off
the electricity much faster
than a fuse or MCB.
Links
Electromagnetism
Revision Questions
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