To ensure application-specific safety, manufacturers make different types of RCCB devices. These are classified based on various factors such as the number of poles or tripping current time. Below, we’ll look at these RCCB types and everything about them, including where and when to use them.
What Does RCCB Stand For?
RCCB stands for Residual Current Circuit Breaker: a type of electrical device used in power systems to prevent electric shock. This is necessary when there’s a difference between the out-going current and in-coming currents in a circuit, such as may result leakage current due to insulation failure.
The RCCB working principle is pretty simple: a current transformer, which has two coils wound around the same magnetic core, detects the current. When there’s a fault and the current begins to leak out into the ground, the resulting current reduction in the neutral wire triggers the RCCB to trip.
RCCB breakers help protect people and property from the dangers of electrical shocks. These are shocks that result from a person coming into contact with exposed live wires or electric fires due to insulation failure. The RCCB will trip and disconnect the electricity supply, thus avoiding any further harm.
Types of RCCB
Different RCCB types are available in the market today. These come in various design features and application-specific capabilities, depending on the type of circuit or power system. Usually, these include types of RCCB based on the number of poles (single and 4-pole) and types of RCCB by tripping curve characteristics (A, AC, F, or B).
Types of RCCB by Number of Poles
A residual current circuit breaker can be a single of four-pole RCCB. The type to use will usually depend on the type of power system, which can either be a single phased or three phased system — as explained in more detail below.
Single Pole RCCB
These types of RCCB breaker are specifically built for single-phase systems. They have one input (live wire), and one output (neutral wire). Because single phase systems are typically low voltage, the single pole or single phase RCCB is mostly used in residential and smaller commercial applications. You’ll also find it being used in small or light industries.
Four Pole RCCB
Unlike the single pole device, the 4-pole RCCB is designed for higher voltage three phase systems. It has three inputs (live wires) and one output (neutral wire). This type of device is often used in industrial settings as it can better handle larger current flows.
Types of RCCB by Tripping Characteristics
When selecting a residual current circuit breaker, you also need to consider the type of tripping features it offers. The four main types RCCB by their tripping capabilities are: A, AC, F and B. These, together with the types of faults they respond to (as well as their best applications) are outlined below:
Type AC RCCB
This is the traditional type of RCCB, designed for use with sinusoidal AC circuits — as its name implies. As such, it cannot reliably detect DC current faults, whether smooth or pulsed. It will also not work with circuits that use different frequencies than the standard 50/60Hz.
Because it only works with sine wave circuits, the type A RCCB is suitable for applications that do not contain electronic components that may produce DC faults: Only use it, therefore, for the traditional appliance.
Type AC RCCB specific applications include the following: such as immersion heaters, incandescent lighting, older electric showers, and similar equipment. Note that these are things that do not contain electronic parts.
Type A RCCB
The type A RCCB can be said to be an upgrade of the AC type. In addition to detecting AC current faults from sinusoidal circuits, it also can detect pulsed DC current faults. As such, it is suitable for use with all types of appliances, including those that contain electronic components.
The applications of the type A RCCB specifically include circuits that contain these appliances: inverters, motor drives, and UPS systems. These types of RCCB will also usually have the symbols for AC and pulsed-DC wave forms, which you can use to easily identify them.
You may also want to know that even though these types of RCCB breakers are designed to protect against the faults of AC and pulsed DC circuits, they will still detect smooth DC currents, but only up to 6mA.
Type F RCCB
The type F RCCB covers all the capabilities of the above two types of RCCB, A and AC, but with ability to sense frequencies other than the standard 50/60Hz. It can detect up to 1000Hz, or 1 kHz, making it well suited for use with variable frequency drives, and other electronic equipment.
Use this type of RCCB for applications where you need to protect persons from the fault currents of modern washing machines, fans, and other equipment that uses a variable frequency drive or supply.
Note that these types of RCCB will as also protect against smooth DC faults for up to 10 milliamps, which is higher than the 6 milliamps that the type A RCCB breaker offers.
Type B RCCB
The type B RCCB combines all the capabilities of the other three types of RCCB (A, AC and F), but with one added feature: the ability to measure and react to smooth DC current faults.
As such, it’s the most versatile type of RCCB, suitable for applications with all types of powered equipment including PV systems, and wind turbines. But then, it’s also the most expensive of the different types of RCCB and not very common.
You may also come across a type B+ version of the device. This type is exactly the same as the B type RCCB, but one that will react to higher frequency faults. While the standard type B RCCB can react to 1 KHz, the type B+ RCCB can detect frequencies of up to 20 KHz.
RCCB Type A Vs. Type B
The most important (and most versatile) types of RCCB breakers are the type A and B. As we have seen, they differ in the way they detect and react to fault currents. Starting with RCCB type A, we can see that you can use it to detect AC and pulsed DC faults.
The type B RCCB, on the other hand, does all A can do, but senses smooth DC currents as well as variable frequency fault currents. It’s also able to detect a slightly higher level of DC current than type A (10 mA compared to 6 mA), which makes it suitable for applications that present DC fault currents.
Despite its many capabilities, though, the B type breaker is the most expensive of them all and not as common as the other types, as its applications are more specific and rare. In most situations, the A type RCCB offers sufficient protection.
Different types of RCCB breakers are meant for use in different applications. Your choice of breaker should be based on the types of fault currents you want to protect against, whether AC or DC, as well as frequency variations if any. Before making your selection, be sure to understand what each type of RCCB can do and that it meets the requirements of your particular application as outlined in this post.