What is the difference between MCB, MCCB, ACB, VCB, ELCB and RCCB

1. WHAT IS THE DIFFERENCE
BETWEEN MCB, MCCB, ACB, VCB,
ELCB AND RCCB
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2. MCB (MINIATURE CIRCUIT BREAKER)
Characteristics
• Rated current not more than 100 A.
• Trip characteristics normally not adjustable.
• Thermal or thermal-magnetic operation.
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3. MCCB (MOULDED CASE CIRCUIT BREAKER)
Characteristics
• Rated current up to 1000 A.
• Trip current may be adjustable.
• Thermal or thermal-magnetic
operation.
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4. ACB (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.
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5. VCB (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.
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6. 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
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7. 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
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8. RCBO (RESIDUAL CIRCUIT BREAKER WITH
OVERLOAD)
Characteristics
• 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
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9. 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.
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10. DIFFERENCE BETWEEN ELCB AND RCCB
• 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.
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11. 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.
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