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MCB (Miniature Circuit Breaker)


  • Rated current less than a hundred A.
  • Trip characteristics commonly not adjustable.
  • Thermal or thermal-magnetic operation.

MCCB (Moulden Case Circuit Breaker)


  • Rated current up to a thousand A.
  • Trip current is also adjustable.
  • Thermal or thermal-magnetic operation.

Air breaker


  • Rated current up to ten,000 A.
  • Trip characteristics typically totally adjustable as well as configurable trip thresholds and delays.
  • Usually electronically controlled—some models square measure microchip controlled.
  • Often used for main power distribution in the giant plant, wherever the breakers square measure organized in draw-out enclosures for easy maintenance.

Vacuum breaker


  • With rated current up to 3000 A,
  • These breakers interrupt the arc during a flask.
  • These also can be applied at up to thirty-five,000 V. Vacuum circuit breakers tend to possess longer life expectations between overhaul than do air circuit breakers.

RCD (Residual Current Device )


  • Phase (line) and Neutral each wire connected through RCD.
  • It visits the circuit once there’s earth fault current.
  • The number of current flows through the section (line) ought to come back through neutral.
  • It detects by RCD. any mate between 2 currents flowing through the section and neutral observe by -RCD and trip the circuit among 30Miliseconed.
  • If a house has associate degree earth system connected to associate degree earth rod and not the most incoming cable, then it should have all circuits protected by associate degree RCD (because u might is not ready to get enough fault current to trip an MCB)
  • RCDs square measure a particularly effective style of shock protection

The widest used square measure thirty mA (milliamp) and a hundred mA devices. A current flow of thirty mA (or zero.03 amps) is sufficiently tiny that it makes it terribly tough to receive a dangerous shock. Even a hundred mA may be a comparatively tiny figure in comparison to the present that will flow in associate degree earth fault while not such protection (hundred of amps)

A 300/500 mA RCCB is also used wherever solely fireplace protection is needed. eg., on lighting circuits, wherever the danger of electrical shock is little.

Limitation of RCCB

  • Standard mechanical device RCCBs are designed to control on traditional offer waveforms and can’t be sure to operate wherever none commonplace waveforms are generated by hundreds. the foremost common is that the 0.5 waves corrected waveform generally known as rhythmical dc generated by speed management devices, semiconductors, computers, and even dimmers.
  • Specially changed RCCBs are obtainable which is able to treat traditional ac and rhythmical
  • RCDs don’t supply protection against current overloads: RCDs notice AN imbalance within the live and neutral currents. A current overload, but massive, cannot be detected. it’s a frequent explanation for issues with novices to switch AN MCB {in a|during a|in AN exceedingly|in a very} fuse box with an RCD. this might be wiped out an effort to extend shock protection. If a live-neutral fault happens (a contact, or AN overload), the RCD won’t trip and will be broken. I observe, the most MCB for the premises can most likely trip, or the service fuse, that the state of affairs is unlikely to guide to catastrophe; however, it’s going to be inconvenient.
  • It is currently doable to urge AN MCB and RCD in an exceedingly single unit, known as AN RCBO (see below). commutation AN MCB with AN RCBO of a similar rating is mostly safe.
  • Nuisance tripping of RCCB: explosive changes in electrical load will cause any low, transient current flow to earth, particularly in recent appliances. RCDs are terribly sensitive ANd operate terribly quickly; they’ll well trip once the motor of a recent deep freezer switches off. Some instrumentation is notoriously `leaky’, that is, generate a tiny low, constant current flow to earth. Some forms of pc instrumentation, and huge tv sets, ar wide according to cause issues.
  • RCD won’t shield against a socket outlet being wired with it’s live and neutral terminals the incorrect manner spherical.
  • RCD won’t shield against the heating that results once conductors aren’t properly screwed into their terminals.
  • RCD won’t shield against live-neutral shocks, as a result of the present within the live and neutral is balanced. therefore if you bit live and neutral conductors at a similar time (e.g., each terminal of a light-weight fitting), you’ll still get a nasty shock.

ELCB (Earth discharge Circuit Breaker)


  • Phase (line), Neutral and Earth wire connected through ELCB.
  • ELCB is functioning supported Earth discharge current.

Operating Time of ELCB:

  • The safest limit of Current that body will face up to is 30ma sec.
  • Suppose body Resistance is 500Ω and Vage to the ground is 230 Volt.
  • The Body current is 500/230=460mA.
  • Hence ELCB should be operated in 30maSec/460mA = zero.65msec

RCBO (Residual electrical fuse with OverLoad)

  • It is doable to urge a combined MCB and RCCB in one device (Residual Current Breaker with Overload RCBO), the principals are similar, however, additional varieties of disconnection are fitted into one package. 

Difference between ELCB and RCCB

  • ELCB is that the recent name and sometimes refers to voltage operated devices that aren’t any longer obtainable and it’s suggested you replace them if you discover one.
  • RCCB or RCD is that the new name that specifies current operated (hence the new name to differentiate from voltage operated).
  • The new RCCB is best as a result of it’ll notice any earth fault. The voltage sort solely detects earth faults that flow back through the most earth wire, therefore, this is often why they stopped being employed.
  • The easy thanks to telling AN recent voltage operated trip is to seem for the most earth wire connected through it.
  • RCCB can solely have the road and neutral connections.
  • ELCB is functioning supported Earth discharge current. however, RCCB isn’t having sensing or property of Earth, as a result of basically part current is adequate the neutral current in a single part. That’s why RCCB will trip once each current are deferential and it stands up to up to each the currents are same. each the neutral and part currents ar totally different meaning current is flowing through the world.
  • Finally each is operating for same, however, the factor is property is a distinction.
  • RCD doesn’t essentially need AN earth association itself (it monitors solely the live and neutral).In addition, it detects current flows to earth even in instrumentation while not AN earth of its own.
  • This means that AN RCD can still offer shock protection in instrumentation that encompasses faulty earth. it’s these properties that have created the RCD additional standard than its rivals. for instance, earth-leakage circuit breakers (ELCBs) were widely used concerning 10 years past. These devices measured the voltage on the world conductor; if this voltage wasn’t zero this indicated a current discharge to earth. the matter is that ELCBs would like a sound earth association, as will the instrumentation it protects. As a result, the utilization of ELCBs isn’t any longer counseled.

MCB choice

  • The first characteristic is that the overload that is meant to stop the accidental overloading of the cable in an exceedingly no-fault state of affairs. The speed of the MCB tripping can vary with the degree of the overload. this is often sometimes achieved by the utilization of a thermal device within the MCB.
  • The second characteristic is that the magnetic fault protection, that is meant to control once the fault reaches a planned level and to trip the MCB at intervals one-tenth of a second. the amount of this magnetic trip offers the MCB its sort characteristic as follows:
  • The third characteristic is that the tangency protection, that is meant to guard against serious faults perhaps in thousands of amps caused by tangency faults.
  • The capability of the MCB to work beneath these conditions provides its tangency rating in weight unit amps (KA). normally for client units, a 6KA fault level is adequate whereas for industrial boards 10KA fault capabilities or higher than is also needed.


Fuse and MCB characteristics

  • Fuses and MCBs square measure rated in amps. The amp rating given on the fuse or MCB body is that the quantity of current it’ll pass ceaselessly. this is often unremarkably known as the rated current or nominal current.
  • Many people assume that if this exceeds the nominal current, the device can trip, instantly. therefore if the rating is thirty amps, a current of thirty.00001 amps can trip it, right? this is often not true.
  • The fuse and also the MCB, albeit their nominal currents square measure similarly, have terribly totally different
  • For example, For 32Amp MCB and thirty Amp Fuse, to make certain of tripping in zero.1 second, the MCB needs a current of 128 amps, whereas the fuse needs three hundred amps.
  • The fuse clearly needs additional current to blow it there in time, however, notice what proportion larger each these currents square measure than the ’30 amps’ marked current rating.
  • There is a little probability that within the course of, say, a month, a thirty-amp fuse can trip once carrying 30 amps. If the fuse has had some of the overloads before (which might not even been noticed) this is often way more doubtless. This explains why fuses will typically ‘blow’ for no obvious reason
  • If the fuse is marked ’30 amps’, however, it’ll truly stand forty amps for over an associate hour, however, will we have a tendency to justify business it a ’30 amp’ fuse? the solution is that the overload characteristics of fuses square measure designed to match the properties of contemporary cables. as an example, a contemporary PVC-insulated cable can stand a five-hundredth overload for an associate hour, therefore it looks affordable that the fuse ought to likewise.

You can watch the following video or read the written tutorial below.