Ling Xiaojie 1 Zhu Dawei 2 Yang Guangliang 2 Huang Wentao 2
(1.Zhejiang Chaowei Architectural Design Institute Zhejiang 310011)
(2. Jiangsu Ankerui Electric Manufacturing Co., Ltd., Jiangyin, Jiangsu 214405, China)
The DC power distribution system usually consists of a high-frequency switching power supply and a battery to provide reliable DC power for control, signal, relay protection and automatic devices, accident lighting, etc. in the DC system, and the reliability and stability of the power supply. Power quality has high requirements. Therefore, it is very urgent to make corresponding modifications to some long-serving DC systems. Moreover, the DC system is not interrupted during the retrofit, and the engineering transformation is difficult. It cannot be solved by the traditional closed-loop Hall current sensor or the shunt. Therefore, the open-type Hall current sensor can be used to solve the DC current measurement problem in the retrofit project to ensure the transformation process. No power failure and safe operation.
1 product design
1.1 Structural features
The open-type Hall current sensor is developed on the basis of the traditional closed-loop Hall current sensor, and has a novel structure and a beautiful appearance. The whole body is composed of outer casing, iron core, sampling circuit board and fixing resin. The outer casing material is made of PC/ABS alloy, which has the characteristics of high temperature resistance, high mechanical strength and environmental protection. The iron core adopts oriented cold-rolled silicon steel sheet with stable performance and mechanical properties. High strength, high magnetic permeability, etc.; green pluggable terminals are used for circuit board and external wiring, and field wiring is convenient and reliable. The specific structure is shown in Figure 1 and 2. The appearance of the product adopts the split design. Figure 1 shows the round hole type, which is suitable for the DC system to pass through when the busbar is the cable. Figure 2 square hole type, suitable for DC system when the busbar is passed through the busbar. According to the measurement range of primary current and the requirements of perforation, the corresponding product type can be selected. The current range of the sensor range is 20A~20000A. The main shapes are Ñ„20, Ñ„40, Ñ„60, 64*16, 85*27, 104*36, 140*50, etc., as shown in Figure 3, suitable for different Application.
.png)
.png)
Figure 1 Round hole type Figure 2 Square hole type
.png)
Figure 3 AHKC Series Open Hall Current Sensor
1.2 Working principle
The Hall current sensor is a sensor designed according to the Hall effect and electromagnetic induction principle. According to the principle, it can be divided into open loop mode (straight discharge type) and closed loop mode (magnetic balance type). The open type Hall current sensor is traditional. The open-loop (direct-release) Hall sensor is improved on the basis of the traditional single-core and single-Hall chip design. In order to design the split structure, the iron core is separated and symmetrically mounted, and the hardware adopts double Hall chips in parallel. Complementary differential input, the principle of open Hall sensor is shown in Figure 4:
.png)
Figure 4 Schematic diagram of open Hall sensor
When the primary current IP flows through a long wire, a magnetic field is generated around the wire. The magnitude of the magnetic field is proportional to the current flowing through the wire. The generated magnetic field is concentrated in the magnetic ring, and the two holes in the air gap through the magnetic ring The components are measured. The two Hall elements are oppositely placed in the same magnetic field. The output signals have complementary characteristics. The output voltage is amplified by differential amplification, which not only suppresses common mode interference, but also affects temperature drift. The output voltage is accurate. Reflects the primary current IP. The typical rated output is calibrated to DC ± 5V or DC 4-20mA.
1.3 Product Installation
Taking the square hole product as an example, as shown in FIG. 5, the mounting screw of the open type Hall current sensor is opened to remove the lower body of the sensor; the upper body of the open type Hall current sensor is loaded into the primary bus of the power distribution system. Close the lower body of the sensor, and fix the mounting screws and washers of the sensor through the fixing holes of the upper and lower bodies to fix the upper and lower bodies of the sensor together. If the site can be powered off, two corresponding threaded holes can be opened on the bronze plate according to the sensor spacing requirements. The sensor is fixed on the female threaded hole through the mounting hole on the rear side to complete the installation of the sensor; The matching rubber pad can be embedded between the outer casing and the bronze plate to ensure that the sensor can work reliably under the vibration condition, and the whole installation process is relatively quick and simple.
.png)
Figure 5 Product installation diagram
1.4 Open Hall Sensor Advantages
Compared with traditional DC current metering, which generally uses a shunt or transformer measurement method, the open Hall sensor has the following advantages:
1) The primary side secondary insulation strength is high, up to AC 12kV isolation;
2) no insertion loss;
3) Good dynamic performance: response time less than 20us tracking speed di/dt higher than 20A/us
4) It is not necessary to disassemble the original cable or busbar during installation, especially for the renovation of power-off equipment.
2. Product application
The open-type Hall current sensor is mainly used in the factory to transform the DC power distribution system, such as the transformation of the power plant DC power system, the transformation of the substation DC system, the transformation of the communication room, the transformation of the railway locomotive, etc. It can convert the primary DC current signal in the system. It is a standard DC±5V or 4-20mA output for monitoring and electrical isolation. It can be used with multi-loop monitoring instruments or other electrical measuring instruments.
2.1 Application examples
Considering the cost of retrofitting, such as the traditional closed-end Hall sensor or shunt scheme, the DC busbar copper busbar must be disassembled before installation, then the sensor should be installed, and then the busbar should be reinstalled and restored, and at least the entire installation process needs to be completed. The two construction workers cooperate with the construction, and at the same time, the rectification of the line must be stopped. In the case of an open-type Hall sensor solution, the installation method described in 1.3 requires only one construction personnel, and the construction time is expected to be only 1/20 of the traditional solution. Time, the power outage time of the factory can also be reduced accordingly, and even in some occasions, the construction and installation of electricity is continuously performed. This scheme is obviously time-saving, labor-saving and labor-saving. From the sensor purchase price comparison, the same type of open-hole shape open Hall sensor is slightly higher than the closed-end Hall sensor purchase price by about 10%. From the aspect of test performance analysis, as long as the upper and lower body screws of the sensor are tightly fixed during installation, the accuracy and stability of the open sensor and the closed sensor are basically the same.
In summary, the use of open-ended Hall current sensors is undoubtedly the most cost-effective solution, both in terms of the superiority of on-site construction and the comprehensive cost considerations of overall project procurement and construction.
Take the DC power distribution cabinet of a well-known domestic enterprise as an example. As shown in Figure 6, the multi-channel DC input is combined into one current output, each of which has protection devices (circuit breakers, fuses, etc.), anti-reverse diodes, etc. Each voltage and current can be monitored and remote communication can be achieved. The eight open-cell Hall current sensors are used to monitor the DC current. The layout is beautiful, which is more convenient than the traditional Hall installation. It is safer and more practical than the shunt scheme.
Figure 7 shows a railway locomotive retrofit project. The retrofit requires monitoring the DC current of the busbar under the premise that the busbar cannot be disassembled. In this case, only the open Hall current sensor scheme can be used.
.png)
.png)
Figure 6 A DC power distribution cabinet of a company Figure 7 A railway locomotive reconstruction project
3 conclusions
In summary, the open-type Hall current sensor plays a large role in the application of the DC system due to its simple structure, convenient installation, reliable operation, etc., especially in the transformation project.
Article source: "Automation Expo" 2015 12 issues.
[1] Power sensor selection manual [Z]. Jiangsu Ankerui Electric Manufacturing Co., Ltd..2015.07.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
Sintered Ndfeb Magnets are the most powerful commercialized permanent magnets available today, with maximum energy product ranging from 26 MGOe to 55 MGOe.
Sintered NdFeB magnets are the most powerful commercialized permanent magnets available today, with maximum energy product ranging from 26 MGOe to 55 MGOe. Nd-Fe-B is the third generation of permanent magnet developed in the 1980s. It has a combination of very high remanence and coercivity, and comes with a wide range of grades, sizes and shapes. With its excellent magnetic characteristics, abundant raw material and relatively low prices, Nd-Fe-B offers more flexibility in designing of new or replace the traditional magnet materials such as ceramic, Alnico and Sm-Co to achieve high efficiency, low cost and more compact devices.
Sintered Ndfeb Magnet,Ndfeb Magnets,Sintered Ndfeb Custom Magnets ,Sintered Ndfeb Neodymium Magnet
Chongqing Great Well Magnet Co.,ltd. , https://www.gwmagnet.com