What is the difference between MCB, MCCB, ELCB, and RCCB
https://engrtechnologies.blogspot.com/2014/03/what-is-difference-between-mcb-mccb.html
What is the
difference between MCB, MCCB, ELCB, and RCCB
MCB (Miniature Circuit Breaker)
CHARACTERISTICS
·
Rated current not more than 100 A.
·
Trip characteristics normally
not adjustable.
·
Thermal or thermal-magnetic operation.
MCCB (Moulded Case Circuit Breaker)
CHARACTERISTICS
·
Rated current up to 1000 A.
·
Trip current may be adjustable.
·
Thermal or thermal-magnetic operation.
Air Circuit Breaker
CHARACTERISTICS
·
Rated current up to 10,000 A.
·
Trip characteristics often fully adjustable
including configurable trip thresholds and delays.
·
Usually electronically controlled—some
models are microprocessor controlled.
·
Often used for main power distribution in
large industrial plant, where the breakers are arranged in draw-out enclosures
for ease of maintenance.
Vacuum Circuit Breaker
CHARACTERISTICS
·
With rated current up to 3000 A,
·
These breakers interrupt the arc in a vacuum
bottle.
These can also be applied at up to 35,000 V. Vacuum circuit breakers tend to have longer life expectancies between
overhaul than do air circuit breakers.
RCD (Residual Current Device / RCCB(Residual Current
Circuit Breaker)
CHARACTERISTICS
·
Phase (line) and Neutral both
wires connected through RCD.
·
It trips the circuit when there is earth
fault current.
·
The amount of current flows through the
phase (line) should return through neutral .
·
It detects by RCD. any mismatch between two
currents flowing through phase and neutral detect by -RCD and trip the circuit
within 30Miliseconed.
·
If a house has an earth system connected to
an earth rod and not the main incoming cable, then it must have all circuits
protected by an RCD (because u mite not be able to get enough fault current to
trip a MCB)
·
RCDs are an extremely effective form of
shock protection
The most widely used are 30 mA (milliamp) and 100 mA
devices. A current flow of 30 mA (or 0.03 amps) is sufficiently small that it
makes it very difficult to receive a dangerous shock. Even 100 mA is a
relatively small figure when compared to the current that may flow in an earth
fault without such protection (hundred of amps)
A 300/500 mA RCCB may be used where only fire protection
is required. eg., on lighting circuits, where the risk of electric shock is
small.
Limitation of RCCB
·
Standard
electromechanical RCCBs are designed to operate on normal supplywaveforms and cannot be guaranteed to operate where none standard
waveforms are generated by loads. The most common is the half wave rectified
waveform sometimes called pulsating dc generated by speed control devices, semi
conductors, computers and even dimmers.
·
Specially modified RCCBs are available which
will operate on normal ac and pulsating dc.
·
RCDs
don’t offer protection against current overloads: RCDs detect an imbalance in the live and neutral
currents. A current overload, however large, cannot be detected. It is a
frequent cause of problems with novices to replace an MCB in a fuse box with an
RCD. This may be done in an attempt to increase shock protection. If a
live-neutral fault occurs (a short circuit, or an overload), the RCD won’t
trip, and may be damaged. In practice, the main MCB for the premises will
probably trip, or the service fuse, so the situation is unlikely to lead to
catastrophe; but it may be inconvenient.
·
It is now possible to get an MCB and and RCD
in a single unit, called an RCBO (see below). Replacing an MCB with an RCBO of
the same rating is generally safe.
·
Nuisance
tripping of RCCB: Sudden
changes in electrical load can cause a small, brief current flow to earth,
especially in old appliances. RCDs are very sensitive and operate very quickly;
they may well trip when the motor of an old freezer switches off. Some
equipment is notoriously `leaky’, that is, generate a small, constant current
flow to earth. Some types of computer equipment, and large television sets, are
widely reported to cause problems.
·
RCD
will not protect against a socket outlet being wired with its live and neutral
terminals the
wrong way round.
·
RCD
will not protect against the overheating that results when conductors are not properly screwed into
their terminals.
RCD will not protect against live-neutral shocks, because the current in the live and neutral is
balanced. So if you touch live and neutral conductors at the same time (e.g.,
both terminals of a light fitting), you may still get a nasty shock.
ELCB (Earth Leakage Circuit Breaker)
CHARACTERISTICS
·
Phase (line), Neutral and Earth wire
connected through ELCB.
·
ELCB is working based on Earth leakage
current.
·
Operating
Time of ELCB:
·
The safest limit of Current which Human Body
can withstand is 30ma sec.
·
Suppose Human Body Resistance is 500Ω and
Voltage to ground is 230 Volt.
·
The Body current will be 500/230=460mA.
·
Hence ELCB must be operated in
30maSec/460mA = 0.65msec
RCBO (Residual Circuit Breaker with OverLoad)
·
It is possible to get a combined MCB and
RCCB in one device (Residual Current Breaker with Overload RCBO), the
principals are the same, but more styles of disconnection are fitted into one
package
Difference between ELCB and RCCB
·
ELCB is the old name and often refers to
voltage operated devices that are no longer available and it is advised you
replace them if you find one.
·
RCCB or RCD is the new name that specifies
current operated (hence the new name to distinguish from voltage operated).
·
The new RCCB is best because it will detect
any earth fault. The voltage type only detects earth faults that flow back
through the main earth wire so this is why they stopped being used.
·
The easy way to tell an old voltage operated
trip is to look for the main earth wire connected through it.
·
RCCB will only have the line and neutral
connections.
·
ELCB is working based on Earth leakage
current. But RCCB is not having sensing or connectivity of Earth, because
fundamentally Phase current is equal to the neutral current in single phase.
That’s why RCCB can trip when the both currents are deferent and it withstand
up to both the currents are same. Both the neutral and phase currents are
different that means current is flowing through the Earth.
·
Finally both are working for same, but the
thing is connectivity is difference.
·
RCD does not necessarily require an earth
connection itself (it monitors only the live and neutral).In addition it
detects current flows to earth even in equipment without an earth of its own.
·
This means that an RCD will continue to give
shock protection in equipment that has a faulty earth. It is these properties
that have made the RCD more popular than its rivals. For example, earth-leakage
circuit breakers (ELCBs) were widely used about ten years ago. These devices
measured the voltage on the earth conductor; if this voltage was not zero this
indicated a current leakage to earth. The problem is that ELCBs need a sound
earth connection, as does the equipment it protects. As a result, the use of ELCBs
is no longer recommended.
MCB Selection
·
The first characteristic is the overload
which is intended to prevent the accidental overloading of the cable in a no
fault situation. The speed of the MCB tripping will vary with the degree of the
overload. This is usually achieved by the use of a thermal device in the MCB.
·
The second characteristic is the magnetic
fault protection, which is intended to operate when the fault reaches a
predetermined level and to trip the MCB within one tenth of a second. The level
of this magnetic trip gives the MCB its type characteristic as follows:
Type
|
Tripping
Current
|
Operating
Time
|
Type B
|
3 To 5 time full load current
|
0.04 To 13 Sec
|
Type C
|
5 To 10 times full load current
|
0.04 To 5 Sec
|
Type D
|
10 To 20 times full load current
|
0.04 To 3 Sec
|
·
The third characteristic is the short
circuit protection, which is intended to protect against heavy faults maybe in thousands
of amps caused by short circuit faults.
·
The capability of the MCB to operate under
these conditions gives its short circuit rating in Kilo amps (KA). In general
for consumer units a 6KA fault level is adequate whereas for industrial boards
10KA fault capabilities or above may be required.
Fuse and MCB characteristics
·
Fuses and MCBs are rated in amps. The amp
rating given on the fuse or MCB body is the amount of current it will pass
continuously. This is normally called the rated current or nominal current.
·
Many people think that if the current
exceeds the nominal current, the device will trip, instantly. So if the rating
is 30 amps, a current of 30.00001 amps will trip it, right? This is not true.
·
The fuse and the MCB, even though their
nominal currents are similar, have very different properties.
·
For example, For 32Amp MCB and 30 Amp Fuse,
to be sure of tripping in 0.1 seconds, the MCB requires a current of 128 amps,
while the fuse requires 300 amps.
·
The fuse clearly requires more current to
blow it in that time, but notice how much biggerboth these currents are than the ’30 amps’ marked
current rating.
·
There is a small likelihood that in the
course of, say, a month, a 30-amp fuse will trip when carrying 30 amps. If the
fuse has had a couple of overloads before (which may not even have been
noticed) this is much more likely. This explains why fuses can sometimes ‘blow’
for no obvious reason
If the fuse is marked ’30 amps’, but it will
actually stand 40 amps for over an hour, how can we justify calling it a ’30
amp’ fuse? The answer is that the overload characteristics of fuses are
designed to match the properties of modern cables. For example, a modern
PVC-insulated cable will stand a 50% overload for an hour, so it seems
reasonable that the fuse should as well.
Hello everyone, I'm Patricia Sherman in Oklahoma USA right now. I would like to share with you my experience of borrowing USD $185,000.00 to clear my bank draft and start a new business. It all started when I lost my house and I took my stuff because of the bank policy and I met some bills and some personal needs. So I became very desperate and started looking for funds in every way. Fortunately for me, a friend of mine, Linda told me about a credit company firm, I was intrigued by the fraud, but I was intrigued by my situation and had no choice but to get advice from my friend about this company. contacting them really doubted me because of my past experience with online lenders, did you know that little? '' Elegantloanfirm@hotmail.com This company has been very helpful to me and my colleague and today, thanks to this credit company, the proud owner of well-organized work and responsibilities, they smiled back at me. So if you really need to grow or start your own business, or if you really need to borrow money in any financial hardship, we recommend you find a financial development opportunity in your business today. {E-mail:} Elegantloanfirm@hotmail.com / whats-app number +393511617486.... online for credit not a victim of scam Thank you.
ReplyDelete