Standard mechanical processing by use of cylindrical grinder, grinding wheel motors are traditionally start-up circuit operation. Start with the rated speed motor running, because the network voltage has certain wave, grinding wheel and the friction load the unceasing change, will affect the speed motor error, the standard grinding wheel motor starting circuit usually only a processing speed, difficult to adapt to the requirements of different size of different processing relative linear velocity, so that the machining processing precision is very difficult to guarantee. So from the improvement of the machining quality and machining efficiency, energy saving etc consideration, the frequency conversion technology application in cylindrical grinder, can get satisfactory effect.
Mechanical processing industry cylindrical grinder processing by a variety of products, the size of different size requirements of machining accuracy. The requirements of the relative speed of the linear velocity in grinding wheel spindle is different, the simple adjustment of speed to meet the workpiece axis of the linear speed processing hard to adjust to the ideal state. And because the process of shaft stem produced in bending stress, in the grinding process will produce the grinding wheel into the moment to different, so to bring the grinding wheel speed/torque output different changes, the corresponding will produce the vibration knife lines/burn grain and so on, it was difficult to ensure that the grinding accuracy, which caused low production efficiency, low rate of high-quality goods.
Along with the power electronic technology development, the technology of frequency conversion of more and more popular, mechanical processing industry in the application of frequency converter received a very good effect. Of the frequency converter stepless speed regulation, soft start, constant torque output greatly satisfy the mechanical processing equipment for constant speed/constant torque requirements.
Cylindrical grinder processing load characteristics
According to different axis of the size of the stem diameter, the grinding wheel speed motor output is equal to the speed of the grinding wheel. The size of the grinding wheel grinding force depends on the output torque of electric motor. In the rotation of spindle drive for high speed of the motor, relative to the grinding wheel tachometer output unchanged, the small diameter workpiece machining, grinding into give less; Processing of large diameter, long axial workpiece, workpiece rotate in the motor speed section, grinding wheel feed big, grinding wheel grinding force also are getting bigger, it is difficult to constant torque motor in constant speed/operation. The speed of change occurs as vibration knife lines/burn lines/machining precision of the change of the. Frequency conversion motor stepless speed regulation, constant torque output just can make up for the defect.
Inverter choice
According to the characteristics of the system operation, consider meet mechanical processing cylindrical grinder use demand and equipment such as investment costs Angle consideration, choose with automatic torque ascending function of the universal V/F inverter. Edom yuan Speecon-7200 MA series as an example, according to the power of the grinding wheel motors use different 18.5 KW / 15 KW of converter, with 15 KW, for example, rated voltage three-phase 380 V, output current 32 A, frequency control 0.5-400 HZ, speed control 0.1%, 150% load ability / 60 S. With automatic torque ascending function, flexible PWM control, which can realize more low noise operation, more than 10 section of the speed control.
The start of the system and speed
Cylindrical grinder Lord grinding wheel motor starting circuit used more star-triangle conversion starting circuit. Replace the original with frequency converter circuit, USES the original contact device often open contacts control the operation of the frequency converter, consider the grinding wheel start of inertia, frequency converter soft start time set to 10 S, stop the brake time setting for 15 S, according to the different types of grinding wheel can start torque in a 80% 50% between adjust setting. System speed through the external adjustable frequency adjust potentiometer, according to the different speed adjustment to the diameter, by motor high speed of the mechanical strength/sound/vibration of the factors such as limit, motor for 60 HZ set the highest frequency; Because of the low speed motor cooling effect is poor, consider rotating speed of the factors and the actual maximum size machining, the lowest frequency set to 35 HZ, benchmark frequency set to frequency 50 HZ. Made up of the load characteristics analysis shows that the section is the constant power properties, low speed section is the constant torque properties, and low speed load demand great torque, overload ability. The benchmark for motor frequency above, to ensure the motor but pressure, the constant voltage variable frequency speed regulation. From motor theory, we can conclude that when the same voltage, frequency increases, the motor of the magnetic flux per extremely with the frequency and decreases; When the motor current for rated current, the maximum allowed torque decreases, and allow the output power constant, speed is constant power, and is suitable for the constant power load. A frequency, the following, to ensure that each motor under constant flux extremely, the V/F = constant variable pressure of variable frequency speed regulation, when the current motor for rated current, motor allow output torque unchanged, belongs to the constant torque control and speed regulation, apply to constant torque load. But when speed is low for motor resistance not negligible, if still keep V/F for constant, the motor torque will be reduced, and can't meet the requirements of the low speed load torque is big, overload ability strong performance, so the method of frequency converter torque automatic compensation function, the choice of the compensation V/F curve amended.
System design matters
The precision grinding emery wheel balance to improve: will the rated speed motor running on, in order to reduce the vibration of the high speed, should improve motor rotor and grinding wheel dynamic balance degree, and to correction.
The cooling speed: because for the way the cold wind fan motor cooling cooling, cooling conditions speed becomes poor, and load torque is larger, the motor temperature will increase, so the minimum speed set to surface temperature difference not more than allow motor is based.
Frequency conversion of frequency converter contain high harmonic, will be in the motor electromagnetic noise, so that the output zero phase noise to install filter, can reduce radioactive interference and induction noise.
A frequency converter to the parameters set project important will reverse/highest frequency/stall function lock!




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