subject: Electrical transformer tap control - transformers, tap, electric control - Electric industry [print this page] Electrical transformer tap control - transformers, tap, electric control - Electric industry
Abstract: This paper analyzes Transformer Mechanical tap the practical use of the main problems during the proceeding, which mainly describes how the mechanical tap transformed into electrical control and the corresponding electrical circuit diagram of the improvement and design.
Key words: salt bath furnace; stalls in operation; tap; temperature
1 Transformer operation stalls I work in a factory heat treatment plant for many years, the shop has two furnaces for hardening of the salt bath. Salt bath furnace requires low voltage, high current to work, it is necessary to change the voltage and current transformers. According to the production process requirements, the transformer has three stalls, corresponding to salt bath for three working conditions: 1 file for the furnace heating; 2 files for the furnace heat; 3 file for quenching. The 1 file, 2 files, 3 files positioned by a mechanical tap to change the salt bath furnace transformer primary winding terminal to achieve, and shift operations to be completed by the operatives. The main circuit and control circuit shown in Figure 1, where 1T is the electronic Potentiometer For the furnace temperature setting & Control.
2 , Mechanical problems in tap 2.1 switch short life As high temperature heat treatment plant, combined with the corrosive salt bath furnace gas produced, so that the working environment around the transformer more bad, but mechanical tap is bakelite structural, mechanical contacts, but also a manual shift mode . Therefore, the switch in the use of the process, bakelite ring deformation caused by heat aging or cracking easily. At peak production, and sometimes a life tap less than a month, each tap can not fix the value of a few thousand dollars, workshop equipment to higher maintenance costs.
2.2 manual gearshift positioning are not allowed to exist, issues such contact is not in place
The mechanical tap transformer is used to change the wiring of the primary winding, as is the three-phase transformer, therefore requested the tap at the same time aligned with the three contacts on the transformer corresponding to the three outlet-side stall . As the tap on the installation of the transformer, from the salt bath furnace very close, often subject to corrosion because of their contacts will cause poor contact; the contact then tap the main circuit in the transformer, the current flowing through large , contact easily damaged. In addition, the manual shift orientation are not allowed to exist, the phenomena of contact is not in place, and the operator must stand on shifting transformer, labor-intensive and subject to high temperature gas fumigation of salt bath, personal safety and health were affected. In summary, the mechanical tap-exist easily damaged, maneuver, maintenance workload and other issues, this will cause the quality of quenching not reach the process requirements and the need to re-freeze the salt bath temperature, etc., to the production and factory is a big loss.
3 , Improved method Address the above problems, we tap on the transformer for the electrical transformation, instead of electric machinery. First, the electrical circuit on the transformation of the original owners. In case of power failure, a mechanical tap-positioning a file, 2 files, 3 files, namely to find the file corresponding to the transformer primary winding terminals, good markers for the main circuit contactor wiring . Which control a file with KMl, KM2 Control 2 files, KM3 Control 3 files, the main circuit wiring as shown in Figure 2a.
Followed by transformation of the control circuit design. Stalls due to replacement of the original circuit by the manual tap done, now removed the main circuit tap, switch to the electrical control, the control circuit must be designed to 1 file, 2 files, 3 files were control, here we consider Cross needed a switch to pre-stall, of course you can adopt a three button operation. With electrical interlocking between the various files to ensure that there is only one stall in the main circuit of the contactor. After transformation, the control circuit wiring as shown in Figure 2b.
Order to facilitate the operator to observe and correct operation, we also designed the stall work instructions circuit shown in Figure 3, allowing operators to understand the salt bath furnace at any time the current work status. Use a square light here, the stalls inside the label affixed to the glass, smart and intuitive. Wiring is complete, to consider the safety of persons and equipment can not connect Power supply Contactor KM case (only the electronic potentiometer Power supply Off), to stall action, observation in the main circuit contactor whether to meet the requirements. Then the power of electronic potentiometer connected to see the files after they have accurate temperature control set temperature: that is to set the temperature, disconnect the contactor selected stalls; below the set temperature, the selected contact stalls automatically pull for heating.
4 , Using results Salt bath furnace transformers operate three stalls from the mechanical tap into electrical control gear, to take in the primary circuit of transformer tap removed, allowing frequent operations into three contactor in the control circuit required the use of pre-cross switch gear, the addition of three intermediate Relay Mainly to show the work of the state to consider salt bath furnace. Electrical cabinet with modifications, the transformation of the whole circuit costs around 500 yuan, while a mechanical tap the price is 400 yuan, the plant's two salt bath furnace to replace an average of not less than 10 Tap only.
Stalls after operation using the electric control, and avoid the manual operation is not in place, and contact problems of corrosion, the equipment put into use by the welcome and praise of workers and easy to operate intuitively, and greatly reduced maintenance workload , the factory saved a lot of maintenance funds. On this basis, we successfully transformed the second transformer tap. Years of use down, some wearing only occasional replacement of components (such as light, intermediate relay contacts, etc.), the effect was good.
