Electrical Info

Miniature Circuit Breaker:


The MCB easily senses the overcurrent caused by the short circuit. The miniature circuit has a very straightforward working principle. Additionally, it has two contacts; one fixed and the other movable.

If the current increases, the movable contacts are disconnected from the fixed contacts, making the circuit open and disconnects them from the main supply.

Moulded Case Circuit Breaker:



The MCCB is a protective device protecting the circuit from overloading. Additionally, it has a switch that is operated manually for tripping the circuit. The device features two arrangements, one for the overcurrent and one for the over-temperature. Moreover, the MCCB consists of bimetallic contact, which contracts and expands when the MCCB temperature changes.

The contacts enable the current to flow via the circuit during normal operating conditions. However, as the current increases beyond the preset value, their contacts warm and expand until the contacts are open. Consequently, the circuit disconnects from the main supply and secures the equipment from damage.

The main difference between the MCB and MCCB is their capacity. On the one hand, MCBs have a rating of under 100 amps with an under 18,000 amps interrupting rating. Moreover, their trip characteristics may not be adjustable since they cater to low circuits primarily.

On the other hand, the MCCB provides amps as low as 10 and as high as 2,500, depending on necessity. They have an interrupting rate ranging from 10,000 to 200,000 amps. Moreover, the MCCB features an adjustable trip element for the more advanced models.

• Other differences between the MCB and MCCB include;
• The MCB’s tripping circuit is fixed and is movable in the MCCB.
• MCBs have less than 100 amps, while MCCBs have as high as 2,500 amps
• In MCB, the remote on/off is impossible, while in MCCB, it is possible by the use of shunt wire
• The MCB is largely used in low circuit current, while MCCB is used for the heavy current circuit
• The MCB is used for low energy requirements (domestic purposes), whereas the MCCB is used in high energy requirement regions (large industries).

Residual Current Circuit Breaker:



RCCB is an electrical wiring device that disconnects the circuit as soon as it detects a current leak to the earth wire. It also protects against electric electrocution or shock caused by direct contact.

RCBO and RCCBs, are residual current protection devices. This protection is achieved by monitoring the current flow in the line and neutral. In a healthy circuit, the current flow via the line equals the return flow in the neutral.

However, this return flow may not be equal to the line’s current flow in the event of any abnormalities. A residual current device will sense such a scenario and interrupt the circuit.

Residual Current Device

Residual Current Breaker

Residual Current Breaker with Over-Current:

The RCBO combines the functionality of an MCB and RCD/RCCB. When there is a current leakage, the RCBO trips the entire circuit. Consequently, internal magnetic/thermal circuit breaker components can trip the electronic device when the circuit is overloaded.

RCDs can protect against electric shocks, residual currents, and earth faults. On the other hand, RCBOs can do what RCDs can do and protect a circuit from short circuits and overload. RCBOs are essentially a combination of MCB and RCCB. As such, it can protect overload and short circuits.

Both electrical devices are typically found in a fuse box, commonly referred to as a consumer unit or breaker panel. Similarly, they both help in the protection of systems.

The MCB doesn’t protect against earth fault. On the other hand, the RCD/RCCB secures the electrical circuit against earth fault

The MCB does not entirely protect humans against shock. However, the RCD protects humans from shock.

The MCB has single, two, three, and four pole options. On the other hand, the RCD lacks the single-pole options but has the two, three, and four-pole options.

The MCBs are mostly used in homes and industries, while the RCD is mostly used in homes.

In VCB, the interruption of electrical current occurs within a structure normally made of ceramic known as a “vacuum blister”. This blister is fully insulated and allows a high rate of vacuum inside.

Inside this blister, there are the fixed and moving contacts. The electric arc starts when the contacts separate and thanks to the vacuum and the dielectric strength (electrical insulation) in the structure, the heat generated during the arc is quickly extinguished.

The main advantage of VCB is that they considerably reduce the risk of fire and require less maintenance.

The Air Circuit Breaker have a compressed air storage inside. This air is released through a nozzle and produces a high-speed jet of air. This air is what is used to extinguish the arc.

ACB are usually used in high and medium voltage field services, generally up to 15KV voltages or for outdoor lines up to 220KV or more, depending on the type.

Their main advantages are their small c size, high-speed response time, little maintenance they need and the considerable reduction in the risk of fire.

OCB are the oldest circuit breaker types and use oil as an insulating medium for arc extinguishing.

In this model, the switch contacts are inside insulating oil and when a fault occurs in the system, the switch contacts open inside the oil. The developing arc forms a hydrogen bubble around it, and the pressure generated prevents the arc from reigniting by accident.

Its main advantage is that it does not require special devices to control the electric arc, in addition to the fact that the oil provides insulation between the contacts after the arc has been extinguished.

The main feature of SF6CB is that they use sulfur hexafluoride gas (SF6) in their operation. This gas has an excellent insulating property that makes SF6CB very effective devices.

Furthermore, SF6 has the property of rapidly recombining after extinguishing the arc, being a much more effective cooling medium than air. Due to these properties, SF6CBs are very effective devices in medium and high voltage systems, since the gas used has excellent dielectric properties, as well as being non-flammable.

Normally, the red cables indicate 11kv or higher voltage.