Disection a Instrument
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Transcript of Disection a Instrument
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Residual Current Circuit Breakers
(RCCB)
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siem
Name:Mayank T.mahajan
Sub:RCCB branch:mechanical
Div:2nd
College:siem
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What is a RCCB?
A residual Current Circuit Breaker or else a ResidualCurrent Device is an electrical wiring device thatdisconnects a circuit whenever it detects that the flow ofcurrent is not balanced between the phase ("hot")
conductor and the neutral conductor.In our day to day life this device is called the trip
switch and it could be considered as the most importantpart of the home wiring system in security aspects.
RCCBs are designed to act or disconnect
very quickly and is the fastest reacting mechanismamong the current circuit breakers.
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References
EE 101 course material
www.howstuffworks.com
www.wikipedia.com
www.crabtree.com
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Our special thanks to
Mr.amit patel
Mrs.saloni patel
Faculty of electrical department
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Domestic and industrial use Residual Current Circuit Breaker. Available in 2 Pole
and 4 Pole . Prevents shocks caused by earth leakage which could be fatal.
.
2 pole
Used for Single phase electrical connections, mostly for domestic purposes.
4 pole
Used for three phase electrical connections, for industrial and commercial
purposes.
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Use of special magnetic materials for the toroidal core
balance transformer and a specially developed highly
sensitive miniature relay ensure positive detection of
earth leakage currents as low as 30mA in less than 40
milli seconds thereby acting as a life saver. All theRCCB's are protected from nuisance tripping against
transit voltages (lighting, line disturbances...) and
transient currents (from high capacitive circuits).
l STOP SHOCK RCCB's are housed in high quality
thermoplastic insulating material. The materials used
are fire retardant, anti tracking, non-hygroscopic,impact resistant and can withstand high
temperatures.
meterials
Mechanism components are made of plastics which
are of high-quality, high-strength, low inertia and self
lubricating properties. This results in a very fast
opening action of the device under fault conditions.
Though the moving components of the mechanism
are made of plastics for friction free and smooth
operation, load bearing parts of mechanism are made
of high-strength steel thus the combination resulting in
making the mechanism more sturdy.
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RCCB's, relay draws the energy from the residual
current which it needs to trip the RCCB that's why it
can still operate normally if the mains voltage drops or
if the neutral wire is interrupted, even a relatively longperiod of over voltage resulting form a fault current in
the mains can't destroy RCCB or interfere with its
normal operation.
RCCB's are provided with an ARC
chamberconsisting of arc-chute. The arc chute
quenches the
arc faster, which further increases electrical
contacts
life.
Apart from suitability to
copper cables the terminals
are suitable for aluminum
cables from 1 to 25 sq mm.RCCB can be easily
mounted on a
standard DIN Rail of 35
mm. Furthermore, operation
of the RCCB is independent
of mounting position.
Supply connections can be
terminated either from top
or bottom.
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Extra protection In the event of direct contact
Zone physiological effects
Fire Protection
To provide extra protection in the event of direct contact with an (unearthed)live part, extremely sensitive RCCB's with a rated residual operating current
of 30 mA or less (I = 30 mA) are used instead of more conventional RCCB's ?n
with higher residual operating fault currents.
This extra protection is necessary if:
l The insulation of totally insulated devices or their loads are damaged.
l The earth wire is interrupted
l The earth wire and live wire are transposed (accidentally thus rendering line
the body of a protection class I device).
l A component which is live in normal operation is touched during repair
work.
In view of this increased range of protection, an RCCB or RCCB/MCB with
I = 30 mA is must - by law in some European countries - to be used when ?n
installing machinery of equipment in areas with particularly high accident
risk.
l Socket-outlet power circuits in rooms with bath or shower.
l Caravans, boats and yachts and their power supply on camping or berthing
sites
l Electrical appliances in rooms used for medical purposes.
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1Usually no reaction effects.
2 Usually no harmful physiological effects.
3 Usually no organic damage to be expected. Likelihood of muscular
contraction and difficulty of breathing reversible disturbance of formationand conduction of impulses in the heart and transient cardiac arrest
without
ventricular fibrillation increase with current magnitude and time.
4 In addition to the effects of zone 3, increasing with magnitude and time
pathy physiological effects such as cardiac arrest, breathing arrest and
heavy burns may occur.
Even relatively insensitive RCCB's (I = 300
mA) can be used to provide ?n
effective protection against fire caused byearth-Ieakage faults.With a residual
current = 300 mA, the electrical energy
released at the location of the earth
fault is not sufficient to ignite normal
building materials.With larger residual
currents, the RCCB switches off the circuitin less than 200 milliseconds, thus
limiting the amount of energy released to a
harmless level.
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Additional Protection Against Pulsating Fault Currents
Precautions forinstallations
Fault finding when RCCB trips
While the tripping of residual current circuit breakers with pure alternatingfault currents was usual and adequate in the past,
these can only be used conditionally in modern electrical installations.
With light controls, speed controls etc. pulsating
forms of current increasingly occur also as fault currents as a result of the
use of electronic components. In order to tackle
such pulsating direct fault currents which tend to zero or almost zerowithin every period of the mains frequency at least for
half a period, 'A' type of RCCB's are suitable. Type A is more sensitive
than AC type. It covers all requirements of AC type
plus it is pulse current sensitive.
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Manufacturing process : EXTRUSION, LAMINATED/ROLLING, DIE COMPACTED
Issues-Limitations
A residual current circuit breaker can improve the safety of an electrical system but cannotremove all risk of electric shock or fire. In particular, an RCD will not detect overload conditions,
phase to neutral short circuits orphase-to-phase short circuits. Some sort of over-current
protection (fuse orcircuit breaker) must be employed to guard against these occurrences.
Combined RCD/circuit breaker units are available, and these combine the functions of an RCD
with those of a conventional circuit breaker, responding appropriately to fault currents and
overload conditions. These are known as RCBOs, and are available in 1, 2, 3 and 4 pole
configurations. RCBOs will typically have separate circuits for detecting current imbalance
(RCD function) and for detecting overload current (circuit breaker function); however the devicefor interrupting the flow of current will be common to both functions.
An RCD will help to protect against electric shock where current flows through a person from a
phase (live / line / hot) to earth. It cannot protect against electric shock where current flows
through a person from phase to neutral or phase to phase, for example where a finger touches
both live and neutral contacts in a light fitting. It is virtually impossible to provide electrical
protection against such shocks as there is no way for a device to differentiate between current
flow causing an electrical shock to a person and normal current flow through an appliance.
Protection against electrical shock of this nature must be through mechanical means (guards or
covers to protect against accidental contact) and procedure (e.g. switching off power before
undertaking maintenance).