What is RCCB | RCCB Working Principal

We discussed about what is RCCB? RCCB Poles Leakage Tripping Rating, Rated Current in RCCB. How to make RCCB connection and Why does RCCB trip? Also RCCB Working Principal, Advantages and Disadvantages of RCCB.

RCCB means Residual Current Circuit Breaker. This circuit breaker is called RCB in some countries. RCB means Residual Current Device. RCCB is used for leakage current protection.

Suppose we have a motor that has no body earthing. In this case if for any reason leakage current is flowing in the motor, or current is flowing in the body of the motor then RCCB will make a trip. Because RCCB provides us with leakage current protection.

How many poles are there  RCCB

  • Two poles
  • Four poles

RCCB usually consists of two and four poles. MCB consists of different poles.

Two types of ratings are used in RCCB

  1. Leakage Tripping Rating
  2. Rated Current

Leakage Tripping Rating


Leakage Tripping Rating indicates how many amperes of leakage current will cause RCCB to trip. It is usually rated at 30mA, 100mA, 300mA.


30mA is usually used in the home. Because 30mA rating RCCB can protect people. A higher rating than RCCB usually does not protect people.


The 30mA Leakage Current Ratting breaker will trip through the 30mA current flowing circuit breaker.


Rated Current


Rated current indicates the maximum ampere current that will flow through this circuit breaker. Suppose a maximum of 10A current can be flowed with a circuit breaker of 10A Rated Current. It is usually 10A, 16A, 32A, 40A, 63A, 100A.


How to make RCCB connection


How to connect RCCB is given in the circuit diagram above RCCB. The direction from which power will be supplied to RCCB is also given in the circuit diagram. Indicates the breaker's input and output. RCCB connection has to be made accordingly.


In 90% of cases, input is usually given from the top and output is given from the bottom. Phase and neutral have to be placed correctly as per the above diagram of RCCB.


According to the RCCB diagram, Newton has to be connected to the pole with N and phase has to be connected to the other pole.


The RCCB should normally be placed before the distribution circuit breaker, otherwise the RRCB should be used as much as the distribution circuit breaker. This is because the incoming current and the outgoing current between RCCB have to be equal.


Why does RCCB trip?


RCCB basically works by measuring the rate of electron flow. The amount of current flowing through the phase wire is the amount of current flowing back through the neutral wire. In fact, there is no problem in the circuit.


RCCB trips if there is any difference between the amount of current flowing through the phase wire and the current flowing through the neutral wire (Leakage Tripping Rating> 30mA).


Because the low current flowing through the neutral means there is some amount of current leakage which is dangerous for human beings.


RCCB has a relay that is operated by magnetic flux. RCCB trips with the help of this magnetic flux.


RCCB Working Principal


From the figure we can see that RCCB has one core. There are two coils on this core, primary and secondary. There are 2 primary coils, one for phase wire and the other for neutral wire. The secondary coil is installed to control the relay coil.

rccb-connection-diagram
When power is supplied to the phase wire, magnetic flux is generated in the primary winding of the phase wire and magnetic flux is generated in the neutral wire when the current returns through the neutral wire.


The magnetic flux is equal to the two inverse magnetic flux canceling out each other. As a result no mutual plus is generated in the secondary coil relay coil.


If less current flows in the neutral wire as a result of leakage current flow, then mutual flux will be generated in the primary coil of the neutral wire. As a result the additional mutual flux generated by the phase wire will generate mutual flux in the secondary coil relay coil and the relay will work.


This will make the relay trip to RCCB This is how RCCB works.


Advantages of RCCB


  • RCCB focuses on Earth Fault and Leakage Current Protection.
  • RCCB is mainly used to protect people from electrical accidents.
  • Wrong connection circuit cannot be operated with RCCB.
  • RCCB can easily determine faulty circuits.


Disadvantages of RCCB


  • RCCB cannot provide short circuit and upload protection.
  • RCCB cannot be used under high load due to low rated current.
  • RCCB cannot be handled due to any small error, which can be handled in MCB or MCCB.


Q1. What is the main problem of RCCB?

ANS: RCCB does not provide short circuit protection and overload protection.


Q2. Where to use RCCB?

ANS: The main MCB is then used, and the RCCB is then connected to the MCB in the distribution box.


Q3. How much quality RCCB is best to use?

ANS: It is better to use 30mA leakage current RCCB.

If you have any doudts.Please let me know

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