Abstract: According to the principle, characteristics and installation mode of the open-type Hall current sensor, the application of the open-type Hall current sensor in the transformation and distribution system of the factory is analyzed, so as to provide a solution for users to realize the intelligent distribution of DC system quickly.

Key words: open type Hall current sensor  DC distribution system  working principle  application

0 Overview
  DC distribution system is usually composed of high frequency switching power supply and battery, which is used to provide reliable DC power supply for control, signal, relay protection and automatic devices, accident lighting and so on in DC system. It has high requirements for the reliability, stability and quality of power supply. Therefore, in the Russian DC system, we matched the DC Hall distribution meter used. During the transformation of DC system, there is no power outage, and the engineering transformation is difficult, and the traditional closed Hall current sensor or shunt can not solve the problem. Therefore, the open Hall current sensor can be used to solve the DC current measurement problem in the transformation project, so as to ensure the safe operation of the transformation process without power outage.

1 Product Design   
1.1Structural features     
  Open-mouth Hall current sensor is developed on the basis of traditional closed-mouth Hall current sensor. It has novel structure and beautiful appearance. The whole is composed of shell, iron core, sampling circuit board and fixed resin. The shell material is made of PC/ABS alloy, which has the characteristics of high temperature resistance, high mechanical strength and environmental protection. The core is made of oriented cold bonded silicon steel sheet, which has the characteristics of stable performance, high mechanical strength and extremely high magnetic conductivity. Green pluggable terminal is used for circuit board and external wiring, which is convenient and reliable for on-site wiring. The specific structure is shown in Figure 1 and 2. The appearance of the product adopts split design. Figure 1 is a round pass, which is suitable for passing through the DC system when the primary bus is a cable. , Fig. 2 square pass, suitable for the DC system when the primary bus is copper bar. According to the measurement range of primary current and perforation requirements, the corresponding product type can be selected. This series of sensors can measure the current range of 20A ~ 20000A, the main shape of the phi 20, 40, 60, 64*16, 85*27, 104*36, 140*50 and other specifications, as shown in Figure 3, suitable for different applications.
 

              
                   Fig. 1 circular pass pattern                                            Fig. 2 Square pass pattern                         

                   
       Figure 3 AHKC series open type Hall current sensor

1.2 Working principle
  Hall current sensor based on hall effect, electromagnetic induction principle, design of a sensor, according to the principle can be divided into the open loop mode (straight) and closed loop mode (magnetic balance type), open hall current sensor is in a traditional open loop (straight) is improved on the basis of hall sensor, is different from traditional single core, single chip design hall, In order to design a split structure, the iron core is separated and installed symmetrically. The hardware adopts parallel complementary differential input of double Hall chips. The principle of open-type Hall sensor is shown in Figure 4:

  Fig. 4 Schematic diagram of open Hall sensor

  When the primary side current IP flows through a long wire, will produce a magnetic field around the wire, the size of the magnetic field and is proportional to the current through the wire, the magnetic field gathered in the circular, through two hall element in the circular air gap measurement, two hall element marks instead placed in the same field, the output signal with complementary characteristics of output voltage by differential amplifier output, Not only can suppress the common mode interference, but also the influence of temperature drift, the output voltage VS accurately reflect the original side current IP. The general rated output is calibrated as DC±5V or DC4-20mA.

1.3 Product installation
  Take square-hole products as an example, as shown in Figure 5, open the mounting screw of the open-type Hall current sensor, and 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 distribution system, and the lower body of the sensor is closed. The mounting screws and gaskets of the sensor pass through the fixing holes of the upper and lower bodies, and the upper and lower bodies of the sensor are fixed together. If on-site power off installation is possible, two corresponding threaded holes can be opened on the bronze plate according to the sensor spacing requirements, and the sensor is fixed on the threaded hole of the bus bar through the rear mounting fixing hole to complete the installation of the sensor; If the site requires continuous electric installation, the supporting rubber pad can be embedded between the shell and the bronze plate to ensure that the sensor can work reliably under vibration conditions. The whole installation process is relatively quick and simple.

 
Fig. 5 Product installation diagram

1.4 Advantages of open type Hall sensor
  Compared with the traditional DC current measurement method generally adopted by shunt or transformer, the open-type Hall sensor has the following advantages:
1) High insulation strength of primary side and secondary side, up to AC 12KV isolation;
2) No insertion loss;
3) Good dynamic performance: the response time is less than 20uS and the tracking speed Di /dt is higher than 20A/ uS
4) There is no need to disassemble the original side cable or bus during installation. It is especially suitable for the transformation and construction of equipment that is not allowed to lose power.

2. Product application
   Open-end Hall current sensor is mainly used in the transformation of DC distribution system in factories, such as DC power system transformation in power plants, DC system transformation in substations, communication room transformation, railway locomotive transformation and other projects. It can convert the central edge DC current signal of the system into standard DC± 5V or 4-20mA output. It plays the role of monitoring and electrical isolation, and can be used with multi-loop monitoring instruments or other electrical measuring instruments. 

3.Conclusion
  Open-end Hall current sensor plays an important role in the application of DC system because of its simple structure, convenient installation, reliable operation and other good applicability, especially in the renovation project.