Difference Between MCB, RCCB & RCBO Circuit Breaker
Main Difference Between MCB, MCCB, ELCB, RCCB (RCD or RCB) and RCBO Circuit Breakers
Different types of circuit breakers are installed and used for safety purposes in both residential as well as commercial and industrial areas. In power distribution, we need circuit breakers at different levels. Depending on the current carrying capacity, breaking capacity and other functions, we select a suitable circuit breaker according to our needs i.e. VCB, SF6, ACB (Air Circuit Breaker), MCCB and then MCB, ELCB, RCCB (RCD) RCBO, or GFCI / AFCI. This is a common hierarchy being followed in power distribution systems.
What is a Circuit Breaker (CB)?
A CB (Circuit breaker) is a device which:
Control (make or break) a circuit manually or by remote control under normal and fault conditions.
Break a circuit automatically under fault conditions (such as overcurrent, short circuit, etc.).
What is an MCB (Miniature Circuit Breaker)?
MCB stands for “Miniature Circuit Breaker”.
Rated current under 100 amps.
Interrupting rating of under 18,000 amps.
Trip characteristics may not be adjusted.
Working principle based on thermal or thermal magnetic operation.
Suitable for low current circuits (low energy requirement), i.e. home wiring.
Generally, used where normal current is less than 100 Amps.
What is an MCCB (Molded Case Circuit Breaker)?
MCCB stands for “Molded Case Circuit Breaker”.
Rated current in the range of 10-2500 amps.
Thermal operated for overload and magnetic operation for instant trip in SC (short circuit conditions).
Interrupting rating can be around 10k – 200k amps.
Trip characteristics are adjustable.
Suitable for high power rating and high energy i.e. commercial and industrial use.
Generally, used where normal current is more than 100 Amps.
Main Difference between MCB and MCCB
The main difference between MCB and MCCB is the interrupt current rating which is up to 1800 amperes for MCB and 10k – 200k Amperes for MCCB.
The following table shows the comparison and major differences between MCB and MCCB for different characteristics.
Keep in mind that both MCB and MCCB are classified as low voltage circuit breakers and the operation principle is based on thermo-magnetic for both devices.
MCB and MCCB Selection
Now the question is that for a situation, where standard current carrying capacity needed is 100A with breaking capacity of 15KA, what should be used? An MCB or MCCB? We assume cost is not very different.
Both are in molded case and having almost similar features especially when we are comparing with fixed thermal setting option of MCCB and they are classified as low voltage circuit breakers. For magnetic setting, we can select MCB as per curve and MCCB will have either fixed setting or can be adjusted.
So what are the criteria to make a selection of MCB or MCCB? Space can be a point of consideration as MCBs are more compact but it doesn’t make a big point as bigger size of MCCB brings many advantages too like better fault clearing mechanism. keep in mind that both MCB and MCCB are low voltage circuit breakers and created to respond to IEC 947 standards (We are going to discuss these standards below)
Actually there is difference in standards they follow. An MCB is supposed to function in accordance to IEC 60898-1 (Unless mentioned otherwise) and so is tested accordingly. While the MCCB is tested in accordance with IEC60947-2. So to understand the difference between MCB and MCCB we need to get a brief idea of these two standards.
Related Post: Difference between Circuit Breaker and Isolator / Disconnector
Difference between IEC 60898-1 and IEC 60947-2
IEC60898-1
It defines behavior of circuit breaker having rated operational voltage not exceeding more than 440V (between Phases), rated current not exceeding more than 125A (We have range 0.5A-125A) and rated short circuit capacity not exceeding more than 25KA (Usually it is 10KAin MCB) . This is designed for unskilled user (or say uninstructed user) and for devices not being maintained consequently. Also pollution degree covered is zero pollution to maximum pollution (degree 2). These are the circuit breakers we find in residential homes, shops, schools and offices electrical distribution switchboards.
Related Post: What is the Difference Between Neutral, Ground and Earth?
IEC60947-2
This standard applies to circuit-breakers, the main contacts of which are intended to be connected to circuits, the rated voltage of which does not exceed 1000 V AC or 1500 VDC. it also contains additional requirements for integrally fused circuit-breakers. It covers a very high range of standard current carrying capacity (We have range of 6A-6300A) and meant for skilled user. The device is also supposed to be properly maintained. Also pollution degree is to be 3 or more. These circuit breakers are industrial applications and protect the power distribution of up to 1000 volts AC. and 1500 volts DC. (For MCBs, MCCBs and ACBs)
So it is clear t These items are different in their fundamentals. An MCB designed for indoor, pollution-free conditions and would not be suitable for harsh, outdoor applications that require pollution degree 3.
Typically, IEC 60898-1 certified Circuit Breakers meet minimally required performance to proof proper protection of household installations: Pollution degree 2, impulse voltage 4kV, isolation voltage is the same as nominal voltage 440V. That is the reason why we usually meet a limited number of technical information printed on Circuit Breakers.
It is not necessary that circuit breakers certified with IEC 60898-1 can’t be certified with IEC 60947-2, but for sure any manufacturer need to obtain certification. Rating of the same MCB can be different for different standards, so, it is highly recommended to check the data properly printed on it.
How to select MCB or MCCB at Different Circuit Levels?
Well, as we have clarified everything in the above sections, the MCB nameplate rating data and selection of proper MCB or MCCB also provides appropriate information. However, the choice between MCB or MCCB is based on certain factors and conditions, such as:
ICS as a % of ICU. (See Difference between ICS and ICU in term of Circuit Breakers)
Maximum Operating Voltage
Insulation voltage
Mechanical operation (endurance and durability)
Breaking Capacity for each Operating Voltage
Below are types of MCBs which shows the magnetic fault protection. Also, to prevent the accidental overloading of the cable at no fault, there is a thermal device in MCB to eliminate the chances of unwanted tripping operation of MCB. For short circuit protection in home appliances, the current rating is about to 6kA while for heavy and industrial operation, it is above the 10kA.
By the way, it depends on your needs and requirement for what you want to install. Many other different factors affect the situation, so you will have to read the next article below as we have added some simple calculation and formulas for MCB installation and selection for electrical wiring.
Difference between ICS and ICU in term of Circuit Breakers.
ICS = Service Braking Capacity (means, circuit breaker can remove the fault, but it may not be usable afterwards.)
ICU = Ultimate Braking Capacity (means, circuit breaker can remove the fault and remain usable)
Characteristic of MCB and FUSE
Both MCB and Fuse rating in Amperes which is known as Nominal Current or Rated Current.
Keep in mind that an MCB or Fuse with rated current of 50A will not trip when current of more than 50A is flowing through it.
The reason is that MCB and Fuse with same rated current has different properties.
For a 63A MCB and 60A Fuse where it should trip in 0.2 sec, MCB will trip at 260A and fuse will trip at 600A. It shows Fuse delay is very high as compared to MCB.
Sometimes, the fuse blows itself without a reason. It may be due to the previous overloads for specific time which has not been noticed.
In case of Fuse, if the rated current is 60A, it will carry up to 80A for an hour or two. This is the same as modern PVC cables hold 50% overload for an hour.
What is an ELCB (Earth Leakage Circuit Breaker)
ELCB stands for “Earth Leakage Circuit Breaker” and it is used for protecting a person from electric shock and injury. The needs of these devices arise because of the increasing number of injuries as well as deaths due to electric shock.
Difference Between MCB, RCCB & RCBO Circuit Breaker
Main Difference Between MCB, MCCB, ELCB, RCCB (RCD or RCB) and RCBO Circuit Breakers
Different types of circuit breakers are installed and used for safety purposes in both residential as well as commercial and industrial areas. In power distribution, we need circuit breakers at different levels. Depending on the current carrying capacity, breaking capacity and other functions, we select a suitable circuit breaker according to our needs i.e. VCB, SF6, ACB (Air Circuit Breaker), MCCB and then MCB, ELCB, RCCB (RCD) RCBO, or GFCI / AFCI. This is a common hierarchy being followed in power distribution systems.
What is a Circuit Breaker (CB)?
A CB (Circuit breaker) is a device which:
Control (make or break) a circuit manually or by remote control under normal and fault conditions.
Break a circuit automatically under fault conditions (such as overcurrent, short circuit, etc.).
What is an MCB (Miniature Circuit Breaker)?
MCB stands for “Miniature Circuit Breaker”.
Rated current under 100 amps.
Interrupting rating of under 18,000 amps.
Trip characteristics may not be adjusted.
Working principle based on thermal or thermal magnetic operation.
Suitable for low current circuits (low energy requirement), i.e. home wiring.
Generally, used where normal current is less than 100 Amps.
What is an MCCB (Molded Case Circuit Breaker)?
MCCB stands for “Molded Case Circuit Breaker”.
Rated current in the range of 10-2500 amps.
Thermal operated for overload and magnetic operation for instant trip in SC (short circuit conditions).
Interrupting rating can be around 10k – 200k amps.
Trip characteristics are adjustable.
Suitable for high power rating and high energy i.e. commercial and industrial use.
Generally, used where normal current is more than 100 Amps.
Main Difference between MCB and MCCB
The main difference between MCB and MCCB is the interrupt current rating which is up to 1800 amperes for MCB and 10k – 200k Amperes for MCCB.
The following table shows the comparison and major differences between MCB and MCCB for different characteristics.
Keep in mind that both MCB and MCCB are classified as low voltage circuit breakers and the operation principle is based on thermo-magnetic for both devices.
MCB and MCCB Selection
Now the question is that for a situation, where standard current carrying capacity needed is 100A with breaking capacity of 15KA, what should be used? An MCB or MCCB? We assume cost is not very different.
Both are in molded case and having almost similar features especially when we are comparing with fixed thermal setting option of MCCB and they are classified as low voltage circuit breakers. For magnetic setting, we can select MCB as per curve and MCCB will have either fixed setting or can be adjusted.
So what are the criteria to make a selection of MCB or MCCB? Space can be a point of consideration as MCBs are more compact but it doesn’t make a big point as bigger size of MCCB brings many advantages too like better fault clearing mechanism. keep in mind that both MCB and MCCB are low voltage circuit breakers and created to respond to IEC 947 standards (We are going to discuss these standards below)
Actually there is difference in standards they follow. An MCB is supposed to function in accordance to IEC 60898-1 (Unless mentioned otherwise) and so is tested accordingly. While the MCCB is tested in accordance with IEC60947-2. So to understand the difference between MCB and MCCB we need to get a brief idea of these two standards.
Related Post: Difference between Circuit Breaker and Isolator / Disconnector
Difference between IEC 60898-1 and IEC 60947-2
IEC60898-1
It defines behavior of circuit breaker having rated operational voltage not exceeding more than 440V (between Phases), rated current not exceeding more than 125A (We have range 0.5A-125A) and rated short circuit capacity not exceeding more than 25KA (Usually it is 10KAin MCB) . This is designed for unskilled user (or say uninstructed user) and for devices not being maintained consequently. Also pollution degree covered is zero pollution to maximum pollution (degree 2). These are the circuit breakers we find in residential homes, shops, schools and offices electrical distribution switchboards.
Related Post: What is the Difference Between Neutral, Ground and Earth?
IEC60947-2
This standard applies to circuit-breakers, the main contacts of which are intended to be connected to circuits, the rated voltage of which does not exceed 1000 V AC or 1500 VDC. it also contains additional requirements for integrally fused circuit-breakers. It covers a very high range of standard current carrying capacity (We have range of 6A-6300A) and meant for skilled user. The device is also supposed to be properly maintained. Also pollution degree is to be 3 or more. These circuit breakers are industrial applications and protect the power distribution of up to 1000 volts AC. and 1500 volts DC. (For MCBs, MCCBs and ACBs)
So it is clear t These items are different in their fundamentals. An MCB designed for indoor, pollution-free conditions and would not be suitable for harsh, outdoor applications that require pollution degree 3.
Typically, IEC 60898-1 certified Circuit Breakers meet minimally required performance to proof proper protection of household installations: Pollution degree 2, impulse voltage 4kV, isolation voltage is the same as nominal voltage 440V. That is the reason why we usually meet a limited number of technical information printed on Circuit Breakers.
It is not necessary that circuit breakers certified with IEC 60898-1 can’t be certified with IEC 60947-2, but for sure any manufacturer need to obtain certification. Rating of the same MCB can be different for different standards, so, it is highly recommended to check the data properly printed on it.
How to select MCB or MCCB at Different Circuit Levels?
Well, as we have clarified everything in the above sections, the MCB nameplate rating data and selection of proper MCB or MCCB also provides appropriate information. However, the choice between MCB or MCCB is based on certain factors and conditions, such as:
ICS as a % of ICU. (See Difference between ICS and ICU in term of Circuit Breakers)
Maximum Operating Voltage
Insulation voltage
Mechanical operation (endurance and durability)
Breaking Capacity for each Operating Voltage
Below are types of MCBs which shows the magnetic fault protection. Also, to prevent the accidental overloading of the cable at no fault, there is a thermal device in MCB to eliminate the chances of unwanted tripping operation of MCB. For short circuit protection in home appliances, the current rating is about to 6kA while for heavy and industrial operation, it is above the 10kA.
By the way, it depends on your needs and requirement for what you want to install. Many other different factors affect the situation, so you will have to read the next article below as we have added some simple calculation and formulas for MCB installation and selection for electrical wiring.
Difference between ICS and ICU in term of Circuit Breakers.
ICS = Service Braking Capacity (means, circuit breaker can remove the fault, but it may not be usable afterwards.)
ICU = Ultimate Braking Capacity (means, circuit breaker can remove the fault and remain usable)
Characteristic of MCB and FUSE
Both MCB and Fuse rating in Amperes which is known as Nominal Current or Rated Current.
Keep in mind that an MCB or Fuse with rated current of 50A will not trip when current of more than 50A is flowing through it.
The reason is that MCB and Fuse with same rated current has different properties.
For a 63A MCB and 60A Fuse where it should trip in 0.2 sec, MCB will trip at 260A and fuse will trip at 600A. It shows Fuse delay is very high as compared to MCB.
Sometimes, the fuse blows itself without a reason. It may be due to the previous overloads for specific time which has not been noticed.
In case of Fuse, if the rated current is 60A, it will carry up to 80A for an hour or two. This is the same as modern PVC cables hold 50% overload for an hour.
What is an ELCB (Earth Leakage Circuit Breaker)
ELCB stands for “Earth Leakage Circuit Breaker” and it is used for protecting a person from electric shock and injury. The needs of these devices arise because of the increasing number of injuries as well as deaths due to electric shock.
No comments:
Post a Comment