Circuit Breaker Overview
A circuit breaker refers to a switching device that can close, carry and break the current under normal circuit conditions and can close, carry and break the current under abnormal circuit conditions within a specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use.
Circuit breakers can be used to distribute electric energy, start asynchronous motors infrequently, and protect power lines and motors. When they have serious overload or short-circuit and under-voltage faults, they can automatically cut off the circuit. Its function is equivalent to a combination of a fuse switch with an overheating and underheating relay, etc. Moreover, it is generally not necessary to change the components after breaking the fault current. It has been widely used.
Power distribution is an extremely important link in the generation, transmission, and use of electricity. The power distribution system includes transformers and various high and low-voltage electrical equipment, and the low voltage circuit breaker is a widely used electrical appliance.
Circuit Breaker Classification
A circuit breaker generally consists of a contact system and an arc extinguishing device, an operating mechanism, release, and a casing. You can divide it into two types: plastic case circuit breakers or universal circuit breakers.
Circuit breakers can be further divided into high voltage circuit breakers or low voltage circuit breakers depending on their intended use. However, the lines between high and low are blurred. High-voltage circuit breakers are generally those that have a voltage greater than 3kV. In our everyday lives, low-voltage circuit breaker are common.
The circuit breaker is itself a type of circuit breaker. It is also known as the universal circuit breaker (frame circuit breaker). It is not possible to say which circuit breakers are included. Commonly used air circuit breaker types include miniature circuit breakers (air switches), installation (molded case) and universal (frame). The most common air circuit breaker is a universal (frame type) circuit breaker.
The Major Roles of Circuit Breakers
The main circuit breaker functions include cutting off and connecting the load circuit and cutting off the fault circuit. In the event of an electrical overload, the circuit interrupter will disconnect the switch. It also has the function of leakage protection. The circuit breaker can be used for electric energy distribution to the power lines and motors. These are the specific functions:
- Circuit breakers serve two main functions: to connect and cut the load circuit and prevent it from expanding. They also ensure safety.
- If there is an electrical overload, abnormal operation, or a fault, the circuit breaker will open the switch to protect electrical appliances and lines. The circuit breaker also has a leakage protection device that provides leakage protection.
3. Circuit breakers are used to distribute electric power, start asynchronous engines infrequently, and protect power lines, and motors. It functions in the same way as a fuse switch or overheating relay and does not require the replacement of parts once the fault current has been broken.
Differences Between Circuit Breaker and Switch
- Different nature
Circuit breaker: a switching device that can close, carry and break the current under normal circuit conditions, and can close, carry and break the current under abnormal circuit conditions within a specified time.
Switch: It is an electronic component that can open a circuit, interrupt the current, or cause the current to flow to other circuits.
- Different categories
Circuit breakers: The circuit breakers can be divided into high-voltage circuit breakers and low-voltage circuit breakers.
Switches: classified by use: wave switch, band switch, recording and playback switch, power switch, pre-selection switch, limit switch, control switch, transfer switch, isolation switch, travel switch, intelligent fire switch, etc.
- Different functions
Circuit breakers can be used for power distribution and infrequent starting of asynchronous motors to protect power lines and motors. When they have serious overload or short circuit and under-voltage faults, they can automatically cut off the circuit. Its function is equivalent to a fuse switch and Overheating relay, etc. It is not necessary to replace parts after disconnecting the fault current. At present, it has been widely used.
It is used to turn low current circuits on or off. The operation method of the isolating switch is as follows: it can pull and close the bypass current of the closed switch; it can pull and close the grounding wire of the neutral point of the transformer, but when the neutral point is connected to the arc suppression coil, it can only be operated when the system has no fault.
Differences between Fuse and Circuit Breaker
The same point is that short-circuit protection can be achieved. The principle of the fuse is to use the current flowing through the conductor to make the conductor heat up. After reaching the melting point of the conductor, the conductor melts, so the circuit is disconnected to protect the electrical appliances and lines from being burned out. It is an accumulation of heat, so overload protection can also be achieved. Replace the melt as soon as it burns out.
The circuit breaker can also realize the short-circuit and overload protection of the line, but the principle is different. It realizes the circuit breaker protection through the bottom magnetic effect of the current (electromagnetic release) and realizes the overload protection through the thermal effect of the current.
When the electrical load in the circuit is close to the load of the fuse used for a long time, the fuse will gradually heat up until it blows. The fusing of the fuse is the result of the combined action of current and time to protect the line, and it is one-time.
When the current increases to exceed the load of the circuit breaker, it will automatically disconnect, so as to protect the circuit from an instantaneous current increase.
Even though they have roughly the same functions and functions, there are still many differences in many places, including differences in protection methods, action speeds, times of use, and working principles. The differences between fuses and circuit breakers are as follows:
- Protection method: The protection method of fuse is in the form of a fuse, and when the fault phenomenon is eliminated, it is necessary to replace the melt to restore the power supply, so it is not convenient for maintenance. The protection method of the circuit breaker is in the form of tripping. After the fault is eliminated, the normal power supply can be restored only through the closing action, so it is much more convenient than the fuse in terms of maintenance and recovery.
- Action speed: The fusing action speed of the fuse can reach the microsecond (μs) level, which means that its speed is much faster than that of the circuit breaker. This capability is usually more suitable for similar fast truncation requirements for installation and use. The tripping action speed of the circuit breaker is at the millisecond (ms) level, which can be seen to be much slower than that of the fuse, so it can only be used in situations where the cut-off speed requirement is not very high.
- Number of times of use: The fuse must be replaced after fault protection has been performed and the melt has been blown. On the contrary, the circuit breaker can be reused in most cases. But in general, the effect of the circuit breaker is stronger and more thorough than the circuit breaker. In general, the circuit breaker is installed on the branch line, and the fuse is installed on the main line in most cases for two-level protection.
- Working principle: First of all, the working principle of the fuse is mainly based on the thermal effect of the current. When the current exceeds the setting value (it needs to know that the setting value of different fuses is also different), the internal fuse will cause the occurrence and fuse. So as to break the circuit, and play the role of protecting the equipment from being burned out by the large current. There are many types of circuit breakers and there are differences in structural principles. Usually, it is because the current is too large that the excitation of the trip coil will cause the circuit breaker to perform the trip action, so as to control the opening and closing action of the circuit breaker.
On some special occasions, there are clear relevant mandatory regulations and requirements that fuses must be used, such as the control and protection of elevators, so circuit breakers cannot completely replace fuses. In addition, the short-circuit time of the thyristor module is very short. In this case, the tripping speed of the circuit breaker cannot meet the short-circuit requirements at all, so the fusing capacity of the fuse is also recognized, and it is soft in buildings. It is widely used in power distribution systems such as starters and frequency conversion.