Application of the most popular frequency converte

2022-08-05
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The application of frequency converter in CNC machine tools

1 introduction

in the mechanical manufacturing industry, when using ordinary machine tools to process complex parts or high-precision batch products, skilled technical workers are required to complete the manual operation. This inefficient tradition makes the operation of the experimental machine more efficient, and the processing method has been unable to meet the needs of the modern manufacturing industry. With the rapid development of computer technology, advanced machining centers and CNC machine tools came into being, and gradually become the mainstream tool machine tools. SJ series speed sensorless vector inverter produced by Hitachi has been rapidly used in machining centers and CNC machine tools due to its unique performance and superior cost performance. Now, Taking Huazhong century star HNC-21 CNC system as an example, the research on the practical application of Hitachi inverter, such as configuration, system connection, mechanical performance, etc. is introduced as follows

2 frequency converter configuration of CNC machine tools

in the speed regulation system of machine tools, the traditional complex gear box type step-by-step speed regulation mode has been greatly improved in CNC machine tools, and a more advanced frequency conversion stepless speed regulation mode is adopted. For 1.5KW three-phase AC motor, Hitachi speed sensorless vector control sj100 series and Hitachi engineering speed sensorless vector control sj300 series 022hfe frequency converter are selected, which can obtain up to 200% of the high starting torque, realize the automatic identification of off-line motor parameters, greatly reduce the speed fluctuation at low speed, and ensure the stability and accuracy of the system. The CNC system, which is composed of Huazhong CNC century star HNC-21, adopts built-in PLC and bus i/o structure. Y[28] and y[29] double byte digital quantity with sign bit d/a conversion form the frequency command of variable frequency spindle. MDI programming is adopted to make debugging and parameter matching easier to realize

3 inverter connection of CNC machine tools

the connection between Hitachi inverter and Huazhong century star HNC-21 CNC system is shown in the attached figure

figure connection diagram between Hitachi frequency converter and Huazhong Century Star CNC system

Hitachi frequency converter provides an analog input port to control the frequency output value of the frequency converter. The analog input terminal group includes terminals such as [l on the control connector and sensors of different sizes are replaced according to the actual test strength], [oi], [o] and [h], where [o] is used for input voltage and [oi] is used for input current. All analog input signals must use analog ground [l]

when Hitachi inverter is connected with Huazhong century star HNC-21 CNC system, terminals [o] and [l] need to be used as input signals of frequency command of inverter. For the logic control connection of the frequency converter, according to the process requirements of the NC machine tool, the use of independent logic test automation does not only mean that the test logic input terminal 1 and terminal 2 of hundreds of samples are carried out every day in the factory as the forward rotation, reverse rotation and stop signals of the frequency conversion spindle, [p24] terminal provides +24v DC power supply for the logic input, and the maximum current is 300mA. In actual use, it should be noted that the main idea of the [p24] terminal is to prevent short circuit with the [l] terminal by strengthening the connection of all departments and aspects

after Hitachi inverter is connected with Huazhong century star HNC-21 CNC system, check its correctness, and set and verify the basic and extended parameters of the inverter. The frequency command parameter A01 is set to 01, and terminal control is selected; The operation command parameter A02 is set to 01, and terminal control is also selected. The acceleration curve F02 is set to 3S, and the deceleration curve F03 is set to 3S. The fundamental frequency parameter A03 is set to 50Hz and the maximum frequency parameter A04 is set to 200Hz. After completing the connection and related settings between Hitachi frequency converter and Huazhong Century Star CNC system, enter the system online test

4 mechanical properties of CNC machine tools

Hitachi frequency converter is used for the spindle speed regulation system of CNC machine tools. During the on-line process, it meets the control requirements of CNC machine tools through no-load test run and loading test. The test data are shown in Table 1 and table 2

Table 1 start the motor under no-load condition to measure the relevant values of the frequency converter

Table 2 plus the relevant values measured under rated load

the online test data show that Hitachi speed sensorless vector control frequency converter has good speed regulation performance and high cost performance, meeting the mechanical characteristics requirements of digital control machine tools. At the Training Conference on the application of numerical control technology in secondary vocational schools jointly held by the Department of vocational education and adult education of the Ministry of education, China Industrial Machinery Federation and the Commission of science, technology and industry for national defense in early 2004, And the conference held by the Higher Education Department of the Ministry of education on the implementation of the training project for technical talents in short supply in manufacturing industry and modern service industry in the field of numerical control technology application in higher vocational colleges has been widely promoted and applied

5 conclusion

Hitachi inverter shows good low-speed torque characteristics in the application practice of CNC machine tools. It has good linearity in matching with CNC, flexible and convenient programming, and broad application prospects

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