Grinding machines and grinding wheel motors used in standard mechanical processing operate according to traditional starting circuits. After the motor is started, it runs at the rated speed. Due to the fluctuation of the grid voltage, the friction load of the grinding wheel workpiece grinding machine changes continuously, which will affect the speed error of the motor grinding machine. The standard grinding wheel motor starting circuit generally only has one processing speed, which is difficult to adapt to different workpiece sizes. The relative linear speed of different grinding machines is required, so that it is difficult to guarantee the processing precision of the workpiece processed by the grinding machine. Therefore, in terms of improving processing quality, processing efficiency, and saving energy, applying frequency conversion speed regulation technology to grinding machines can achieve satisfactory grinding machine results.
There are many types of grinding machine products processed by grinding machines in the machining industry. The workpieces are of different sizes and require different processing accuracy. Relative to the grinding machine, the speed of the grinding wheel is different from the linear speed of the spindle grinder. It is difficult to adjust the speed of the spindle grinder to meet the processing line speed of the workpiece grinding machine to an ideal state. In addition, due to the stress bending of the grinding machine produced by the processing of shafts, the grinding process will produce different feeding torques of the grinding wheel, which will lead to changes in the output speed/torque of the grinding wheel, and the corresponding grinding machine will produce vibration knife lines/burning lines, etc. , The grinding accuracy is difficult to guarantee, resulting in low production efficiency and low quality rate.
With the development of power electronics technology grinding machines, frequency conversion speed regulation technology grinding machines are becoming more and more popular, and the application of frequency converter grinding machines in the machining industry has received good grinding machine results. Inverter grinding machine with stepless speed regulation, soft start, and constant torque output The grinding machine meets the requirements of mechanical processing equipment for constant speed/constant torque grinding machines.
2. Grinding machine processing Grinding machine load characteristics:
According to the size of the diameter of the shaft of the grinding machine, the speed of the main grinding wheel motor is equal to the output speed of the grinding wheel. The size of the grinding force of the grinder depends on the output torque of the grinder motor grinder. The high-speed section of the main shaft motor of the rotary grinding machine that drives the workpiece has a constant output speed relative to the grinding wheel, and the diameter of the processed grinding machine workpiece is small, and the grinding feed is small; If the feed rate is large, the grinding force of the grinding wheel will also increase, and it is difficult for the motor to run under constant torque/constant speed. Changes in the speed of the grinder produce changes in the grinder such as vibration knife lines/burning lines/processing accuracy. Frequency conversion speed regulation motor grinding machine stepless speed regulation, constant torque output can just make up for the above defects.
3. Frequency converter grinding machine selection:
According to the characteristics of the grinding machine running in the system, and in consideration of meeting the requirements of the mechanical processing grinding machine and the equipment investment cost, etc., the grinding machine vector frequency converter with automatic torque boost function is selected. Taking the SANCH-S2000 series as an example, 18.5KW/15KW grinding machine inverters are selected according to the power of the grinding wheel motor grinding machine. Taking 15KW as an example, the rated voltage is three-phase 380V, the output current is 32A, the frequency control is 0.5-400HZ, the speed control is 0.1%, and the over Load capacity 150%/60S. With automatic torque boost function, flexible PWM control, can achieve lower noise operation, more than 10 stages of grinder speed control.
4. System grinder startup and speed regulation:
The starting circuit of the grinding machine’s main grinding wheel motor mostly uses a star-delta conversion starting circuit. Replace the original circuit with a frequency converter, use the normal open contact of the original contactor grinder to control the operation of the frequency converter grinder, consider the inertia of the grinding wheel to start the grinder, set the soft start time of the frequency converter to 10S, and set the stop braking time to 15S. The starting torque of the grinding wheel of the type grinding machine can be adjusted and set between 50%–80%. The system speed is adjusted by an external adjustable potentiometer, and the grinding machine adapts to the speed adjustment according to the diameter of the workpiece. Due to the mechanical strength/noise/vibration and other factors of the grinding machine when the motor is at high speed, the maximum frequency of the motor is set to 60HZ; due to the heat dissipation of the motor at low speed The effect is poor, considering the variable speed factor of the workpiece rotary grinder, the actual maximum processing workpiece size, the minimum frequency is set to 35HZ, and the reference frequency is set to 50HZ.
From the previous analysis of the load characteristics of the grinding machine, it can be seen that the high-speed section is of constant power, and the low-speed section is of constant torque. At low speed, the load requires large torque and strong overload capacity. For motors above the reference frequency, in order to ensure that the motor does not overvoltage, constant voltage frequency conversion speed regulation is adopted. According to the motor theory, when the voltage is constant and the frequency increases, the magnetic flux per pole of the motor decreases with the increase of the frequency; when the motor current is the rated current, the maximum allowable output torque decreases, and the allowable output The power is constant, which belongs to constant power speed regulation, and is suitable for constant power loads. Below the base frequency, in order to ensure that the magnetic flux of each pole of the motor remains unchanged, V/F=constant variable voltage and variable frequency speed regulation is adopted. When the motor current is the rated current, the allowable output torque of the motor remains unchanged, which belongs to constant torque regulation. speed, suitable for constant torque loads. However, when the speed is low, the internal resistance of the motor cannot be ignored. If the V/F is still kept constant, the motor torque will decrease, which cannot meet the load requirements at low speed. Grinder torque automatic compensation function, choose to correct the V/F curve of the grinder after compensation. 5. System Design Grinding Machine Notes:
Grinding wheel balance grinding machine precision should be improved: run the motor at the rated speed, in order to reduce the vibration of the grinding machine at high speed, the dynamic balance of the motor rotor grinding wheel grinding machine should be improved and corrected.
Heat dissipation of the grinding machine at low speed: Since the motor is cooled by a self-cooling fan, the heat dissipation condition becomes worse at low speed, and the load torque is large, and the temperature of the motor will increase. Therefore, the minimum speed of the grinder is set so that the surface temperature difference of the motor does not exceed the allowable value in accordance with.
During frequency conversion and speed regulation, because the output of the frequency converter contains high-order harmonics, the motor will generate electromagnetic noise. Therefore, a zero-phase noise filter should be installed at the output end to reduce auxiliary radiation interference and induced noise.
Inverter grinder parameter setting items are important to lock reverse/maximum frequency/stall and other functions!
This article analyzes the application of grinding machines on grinding machines in the machining industry of frequency converters in detail. As the main motor of the grinding wheel of power grinding machines, frequency conversion speed regulation technology is introduced to meet the needs of grinding machines for various shaft types, improve work efficiency, and improve the shaft type. Grinding grinding machine processing quality, saving energy. Combined with the actual on-site grinding machine application, the operator’s response is more handy, the surface is smooth and the imaging degree is high, and the yield rate is greatly improved.
