1.Overview：

Along with the development of the power electronics technology grinding machine, the frequency inverter is more and more popular, and the frequency inverter grinder is applied in the machine processing industry.The machine adopts the characteristics of variable frequency speed regulation, soft starting, maximum power output of constant torque, etc., which can adapt to the use of constant torque or constant speed grinding machine.

The standard machine tool uses a grinding machine, and the grinding wheel motor runs according to the conventional drive line. When the motor starts to work at the rated speed, due to the effect of the power grid voltage, the grinding load of the grinding wheel on the workpiece will also change, which will affect the speed of the machine tool. At present, the commonly used grinding machine motor drive circuit usually has only one processing speed, which is difficult to meet the needs of the relative linear speed of different grinding machines for different workpiece sizes, which makes the processing accuracy of the workpiece processed on the grinding machine difficult to be guaranteed.

Therefore, in order to improve the processing quality, improve the processing efficiency, save energy, the use of frequency inverter control technology on the grinding machine can achieve better processing results.

In the machine tool manufacturing industry, due to the different size of the workpiece, its processing accuracy is also different.Relative to the grinder, the speed of the grinding wheel is not the same as the linear speed of the spindle grinder. The speed of the spindle grinder is difficult to adjust to the machining machine.In addition, in the grinding process, due to the role of the grinder stress, different torques will be produced during the grinding process, thereby changing the output speed/torque of the grinding wheel, resulting in blade oscillation/wire burning and other phenomena, thus affecting the precision of grinding, reducing the production efficiency and quality of the product.

The speed of the main wheel motor is equal to its output speed and is proportional to the diameter of the main shaft. During the grinding process, the grinding force is determined by the output torque of the grinding wheel motor.In the high-speed part, the output speed of the grinding wheel is faster, the grinding diameter is smaller, and the tool feed is smaller. In large-diameter grinding, it is difficult to achieve constant torque and constant speed grinding because of the large low-speed part of the grinding wheel.Changes in grinding machine speed, such as grain/grain/cutting accuracy. The motor grinding machine with variable frequency speed regulation and constant torque output method can solve the above shortcomings well.

2.Implementation plans：

Based on the features of the system running grinder and taking into account the cost of the equipment, we choose a vector inverter which can raise the torque automatically. Taking FGI FD100 series frequency inverter as an example, this paper chooses the 18.5KW/15KW grinding frequency inverter based on the power of grinding wheel motor. Taking 15KW as an example, the rated voltage is 380V, the output current is 37A, the frequency is controlled from 0 to 500 Hz, and the over-load capacity is 120%/60S. It has the function of automatically raising the torque, flexible PWM control, can realize the low noise operation, and can control the speed of more than 10.

Based on the analysis of the load characteristics of the front grinding machine, it is found that the high speed part is constant and the low speed is constant. As for the above-mentioned motor base frequency, the constant voltage frequency inverter is used to make sure that the motor is not under pressure. Based on the theory of motor, when the voltage is constant and the frequency is increased, the magnetic field of the motor is reduced. when the motor current is rated, the maximum permissible output torque is reduced and the permissible output power is kept constant.Under the basic frequency, in order to keep the magnetic flux constant, V/F = constant grinding variable voltage variable frequency is used. The permissible output torque is constant when the electric machine grinding machine is rated current. It belongs to constant torque control and is applicable to constant torque load. However, when the speed is low, it is not possible to neglect the inner resistance of the motor. If V/F remains constant, the motor torque will decrease, so it can not satisfy the low speed load, and the grinding torque and overload capability are higher. For this reason, the frequency inverter grinding machine is automatically compensated, and the grinding machine V/F curve is chosen to correct.

3.Application advantage

The FGI FD100 series frequency inverter processing machine is applied in the industry. It is used as a power grinding machine for grinding wheel. It is suitable for all kinds of shaft grinder. Combined with the practical use of field grinding machine, the operator's response is more convenient, the surface is smooth, the image quality is high, and the yield is greatly increased.