This article is mainly about the introduction of frame circuit breakers and molded case circuit breakers, and focuses on the differences between frame circuit breakers and molded case circuit breakers.
Air circuit breakerCircuit breaker: a mechanical switching device that can switch on, carry and break current under normal circuit conditions, and can also switch on, carry and break current for a certain period of time under specified abnormal circuit conditions.
The main components of a fixed frame type circuit breaker are: circuit breaker body, trip unit, and accessories.
The main components of a withdrawable frame type circuit breaker are: circuit breaker body, moving part, fixed part, trip unit, and accessories.
In the design of civil buildings, low-voltage circuit breakers are mainly used for line overload, short circuit, over current, loss of voltage, under voltage, grounding, leakage, automatic switching of dual power supplies, and protection and operation of infrequent starting of the motor. Its selection Principles In addition to complying with the basic principles such as the use environment characteristics of low-voltage electrical equipment (see Industrial and Civil Power Distribution Design Manual), the following conditions should be considered:
1) The rated voltage of the circuit breaker should not be less than the rated voltage of the line;
2) The rated current of the circuit breaker and the rated current of the overcurrent release are not less than the calculated current of the circuit;
3) The rated short-circuit breaking capacity of the circuit breaker is not less than the maximum short-circuit current in the line;
4) The selection of type distribution circuit breakers needs to consider the short-time short-circuit making and breaking capacity and the coordination between the time-delay protection levels;
5) The rated voltage of the undervoltage release of the circuit breaker is equal to the rated voltage of the line;
6) When it is used for motor protection, the starting current of the motor should be considered when selecting the circuit breaker and it should not operate within the starting time; for the design calculation, please refer to the "Industrial and Civil Power Distribution Design Manual";
7) The selection of the circuit breaker should also consider the selective coordination of the circuit breaker and the circuit breaker, and the circuit breaker and the fuse.
(1) The coordination of the circuit breaker and the circuit breaker should consider the instantaneous release action value of the upper-level circuit breaker, which should be greater than the maximum expected short-circuit current at the outlet end of the lower-level circuit breaker. If the impedance value of the loop element is different when the two-stage circuit breaker is short-circuited If the short-circuit current value is small, so that the short-circuit current value is not much different, the upper-level circuit breaker can choose the trip unit with short time delay.
(2) The current-limiting circuit breaker will trip within a few milliseconds when the short-circuit current is greater than or equal to the setting value of its instantaneous release. Therefore, it is not advisable to use a circuit breaker to achieve selective protection requirements for lower-level protection appliances.
(3) For a circuit breaker with short delay, when its time limit is set at the maximum delay, its making and breaking capacity decreases. Therefore, in the selective protection circuit, consider choosing the short delay making and breaking capacity of the circuit breaker to meet the requirements. .
(4) It should also be considered that the short-circuit delay return characteristic of the upper-level circuit breaker and the action characteristic time curve of the lower-level circuit breaker should not intersect, and the short-delay characteristic curve and the instantaneous characteristic curve should not intersect.
(5) When the circuit breaker and the fuse are used together, the coordination of the upper and lower levels should be considered. The ampere-second characteristic curve of the circuit breaker should be compared with the ampere-second characteristic curve of the fuse, so as to have protection selectivity in the event of a short-circuit current. .
(6) When the circuit breaker is used for the protection of the distribution circuit, a circuit breaker with a long delay action overcurrent release should be selected. When a single-phase grounding short circuit occurs at the end of the line, the short circuit current should not be less than the instantaneous or short delay time of the circuit breaker 1.5 times the setting current of the overcurrent release.
Molded Case Circuit BreakerMolded case circuit breakers are also called device-type circuit breakers. All parts are sealed in a plastic case. The auxiliary contacts, undervoltage releases and shunt releases are mostly modularized. Due to the very compact structure, the molded case circuit breaker cannot be overhauled. It mostly adopts manual operation, and large capacity can choose electric opening and closing. Due to the application of electronic over-current releases, molded case circuit breakers can also be divided into two types: A and B. Type B has good three-stage protection characteristics. However, due to price factors, thermal magnetic releases are used. Class A products have a higher market share. Molded case circuit breaker is the contact, arc extinguishing chamber, trip unit and operating mechanism are all installed in a plastic shell, generally do not consider maintenance, suitable for branch circuit protection switch, overcurrent release has thermomagnetic There are two types of thermal-magnetic molded case circuit breakers. Generally, the thermal-magnetic molded case circuit breaker is a non-selective circuit breaker. There are only two protection methods: overload long delay and short circuit instantaneous protection. Electronic molded case circuit breakers have overload long delay and short short circuit protection. Four protection functions: time delay, instantaneous short circuit and ground fault. Some of the newly launched products of electronic molded case circuit breakers also have a regional selective interlocking function. Most molded case circuit breakers are manually operated, and some have motor operating mechanisms.
working principle
The main contact of the low-voltage circuit breaker is manually operated or electrically closed. After the main contact is closed, the free trip mechanism locks the main contact in the closing position. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply. When the circuit is short-circuited or severely overloaded, the armature of the overcurrent release pulls in, causing the free tripping mechanism to operate, and the main contact disconnects the main circuit. When the circuit is overloaded, the thermal element of the thermal trip unit generates heat to bend the bimetallic strip, pushing the free trip mechanism to act, and the main contact disconnects the main circuit. When the circuit is under-voltage, the armature of the under-voltage release is released, which also causes the free trip mechanism to act, and the main contact disconnects the main circuit. When the shunt trip button is pressed, the armature of the shunt trip unit pulls in, causing the free trip mechanism to act, and the main contact disconnects the main circuit.
Working conditions
◠Ambient air temperature ○ Upper limit of ambient air temperature +40℃; ○ Lower limit of ambient air temperature -5℃; ○ The average value of ambient air temperature for 24 hours does not exceed +35℃. ◠Altitude: The altitude of the installation site does not exceed 2000m. ◠Atmospheric conditions: the relative humidity of the atmosphere does not exceed 50% when the ambient air temperature is +40℃; it can have a higher relative humidity at a lower temperature; the average maximum relative humidity of the wettest month is 90%, and at the same time the month The monthly average minimum temperature of +25℃, and taking into account the condensation on the surface of the product due to temperature changes. ◠Pollution degree: The pollution degree is level 3.
The difference between frame circuit breaker and molded case circuit breakerSimply put, it is the difference in size. Not only is the frame circuit breaker larger than the molded case circuit breaker in terms of dimensions, but also the current rating and segmentation capacity of the frame circuit breaker are greater than that of the molded case circuit breaker. This is an essential difference. Therefore, the application occasions of frame circuit breakers and molded case circuit breakers are different. The frame is used for the upper level of incoming lines, and the molded case is used for the lower level of the frame.
Molded case circuit breakers and frame circuit breakers are both very common products used in circuit breaker products. However, many people do not fully understand the difference between the two, and often hesitate when purchasing. Some customers I face often have such troubles, so I consulted three senior engineers in the factory based on this question, and summarized some of their usual purchase experience. Here, I will talk about the plastic case circuit breaker and The difference between the two frame circuit breakers, and the points that need to be paid attention to when selecting. Frame circuit breaker has high segmentation capacity and perfect function-Engineer 1
The plastic case circuit breaker adopts a plastic structure. The characteristic is that the circuit breaker shell and frame are pressed by plastic. The contacts and the arc extinguishing system are placed in an insulated small room to prevent short circuits between phases, to ensure that the arc is sprayed upward, and the contacts are guaranteed. The system is disconnected reliably. The frame circuit breaker adopts a modular structure and is divided into a frame, a contact arc extinguishing system, a manual operating mechanism, an electric operating mechanism, an intelligent controller, and a drawer seat. Each part becomes a complete and independent part, and only 1-2 screws are needed to fix it during assembly. The disassembly and assembly are very convenient for maintenance.
Molded case circuit breakers have a wide range of products, which are characterized by compact structure, easy operation, and relatively simple functions. They are generally equipped with overcurrent releases and instantaneous releases, while frame circuit breakers have perfect functions, especially the application of single-chip technology in recent years. Frame circuit breakers are developing in the direction of high performance, easy maintenance and networking.
In terms of rated current, molded case circuit breakers are generally below 630A (some new products can reach 1600A), while the rated current of frame circuit breakers is much larger, generally 630A-6300A (such as our company’s DW15, DW16 and DW17 series Frame circuit breakers have reached this standard). In addition, frame circuit breakers are higher than molded case circuit breakers in terms of segmentation capacity.
In practical applications, circuit breakers should be used for circuits above 800A or circuits with particularly high requirements for segmentation capabilities or circuits requiring more functions. For circuits below 630A, plastic case circuit breakers are generally used. Molded case circuit breakers are suitable for branch circuit protection switches-Engineer 2
All parts of the frame circuit breaker are installed in an insulated metal frame, which is usually open type, and can be equipped with a variety of accessories. It is more convenient to replace the contacts and parts, and it is mostly used in the main switch at the power end. There are several types of overcurrent releases, such as electromagnetic, electronic and intelligent releases. The circuit breaker has four-stage protection of long time delay, short time delay, instantaneous and ground fault, and the setting value of each protection is adjusted within a certain range according to its shell frame level. Both manual and electric operation are available. With the development of microelectronics technology, some intelligent circuit breakers currently have a regional selection interlocking function, which fully guarantees the sensitivity and selectivity of the action.
Molded case circuit breakers are ground wire terminal outer contacts, arc extinguishing chamber, trip device and operating mechanism, etc. are all installed in a plastic shell, generally do not consider maintenance, suitable for branch circuit protection switch, overcurrent trip device There are two types of electromagnetic and electronic. Generally, electromagnetic molded case circuit breakers are non-selective circuit breakers, and only have long delay and instantaneous protection methods. Electronic molded case circuit breakers have long delay, short delay, Four protection functions for instantaneous and ground faults. Some of the newly launched products of electronic molded case circuit breakers also have a regional selective interlocking function. Most molded case circuit breakers are manually operated, and some are operated with electric motors.
Analysis of the tripping fault of air circuit breaker1. Analysis of the principle of the tripping fault of the air circuit breaker
All trips of the air circuit breaker are centered around the opening half axis. When a fault is analyzed, it is necessary to analyze whether there is a problem with the components connected to the opening half axis, such as the trip coil controlled by the air circuit breaker controller, the opening button, and the undervoltage trip. The tripping device, the trip lever of the mechanical interlock, and some interlocking of the circuit breaker within the opening and closing mechanism are all connected with the opening half shaft. When a tripping fault occurs, these components must be combined for analysis, for example, field tripping , First observe whether the controller on the panel reports a fault and whether the reset button pops up. If it pops up, check the fault information displayed on the controller to see what caused the trip and make corresponding treatments, for example, if a short-circuit fault is displayed , You need to check the circuit below the outlet end of the circuit breaker to find out the fault point. If it shows overcurrent, you need to calculate the load and measure the current to see if there is an overload phenomenon. (Need to check the controller setting value to see if the setting value is correct)
If the controller does not report a fault, the reset button does not pop up, and there is a trip, you need to check whether the circuit breaker is rocked to the position, check whether the baffle of the circuit breaker rocking in and out is in place, is it due to some interlocking of the circuit breaker itself that caused the trip , Pay attention to asking the person in charge of the equipment whether there is an electrical interlock that causes a trip (undervoltage interlock)
After eliminating the above reasons, it may be the undervoltage coil and the opening coil that caused the trip. At this time, you need to check whether the two coils are faulty. First, shake the circuit breaker to the test position, open the circuit breaker mask, and secondly Power on the circuit, observe whether the undervoltage coil is operating normally, and press the opening button to observe whether the opening coil is operating normally. If there is a fault, replace it, and observe whether the position of the opening semi-axle is correct and whether the amount of buckle is sufficient If it is abnormal, it needs to be adjusted.
It is also possible that there is a problem with the controller and its base, which causes the trip coil to act abnormally (shown as the reset button pops up and the controller displays abnormally), current transformer failure causes current sampling errors and trips (some 2 incoming lines 1 The bus tie system has mechanical interlocking, and sometimes the mechanical interlocking adjustment is not in place, which will cause tripping)
2. On-site treatment
After arriving at the site, first observe the appearance of the circuit breaker, check the information on the controller, what fault is displayed, whether the reset button pops up, check the arc extinguisher, whether there is an obvious smell, touch the circuit breaker body to see if the temperature is high High, look at the inlet and outlet copper bars of the circuit breaker, check whether there are foreign objects, whether the transformer is damaged, pay attention to ask the electrician on duty to see if there is a short circuit and overload, look at the transformer capacity and the rated current of the circuit breaker, and check whether the selection If it is correct, take corresponding measures and check the setting parameters of the controller to see if it is correct. After obtaining the user’s consent, shake the circuit breaker to the test position and perform electric opening and closing and manual opening and closing tests. If it cannot be electric, it means that there is no problem with the opening mechanism. The main check is the electric opening and closing circuit. If electric or manual operation is not possible, it means that there may be a problem with the mechanism (electric opening and closing circuit failure is not ruled out). At this time, when electric opening and closing operations are required, listen carefully to the sound of the circuit breaker to see if the coil is operating, open the mask, and observe Whether the coil action is in place, if it is, the problem of the secondary circuit is eliminated. This is to carefully observe the mechanism action during manual opening and closing to see what caused the trip, mainly observe the opening half-axis action, see Whether the amount of buckle is sufficient, if not enough, it needs to be adjusted.
ConclusionThis is the end of the relevant introduction about frame circuit breakers and molded case circuit breakers. If there are any shortcomings, please correct me.
Related reading recommendation: Circuit breaker classification analysis Related reading recommendation: Circuit breaker specification introduction- The Description of wifi Antenna
-
When selecting the antenna, it is necessary to pay attention to whether the connector of the antenna matches the connector of the connected device. Generally, SMA and TNC are used for WIFI
To use on the router, but on the 2.4 G wireless monitoring equipment fittings, if match, also can achieve the enhancement effect of the wireless signal transmission Magnetic antenna base, can suck on metal surfaces, makes the antenna signal is stronger Plug and play, without any additional conditions, but the antenna gain and directional property management are key points to consider. - The first standard WIFI antenna products were made by LTCC process, because of its width and general performance. Abroad, Airgain has launched a standard antenna with high temperature resistance and plastic seal, which is used in laptop computers, and a series of WiFi antennas with magnetic dielectric in mobile phones have been launched in China.
- The Picture of wifi Antenna
-
Wifi Internal Antenna,Wifi Antenna for PC,Wifi Antenna for Router,Wfi Antenna outdoor,Wifi Antenna Indoor
Yetnorson Antenna Co., Ltd. , https://www.xhlantenna.com