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How to adjust the speed of the inverter?

Nov 23, 2020

How to adjust the speed of the inverter?

Variable frequency speed regulation is the most commonly used speed regulation method for three-phase asynchronous motors. It mainly uses variable frequency speed regulation, which has a higher speed regulation range than pole-changing logarithmic speed regulation and variable slip speed regulation. Speed regulation is also very high in terms of speed regulation accuracy. Let me discuss with my friends how to adjust the speed of the inverter. The basic principle of variable frequency speed regulation The basic theoretical basis of variable frequency speed regulation is based on n=60f/p, in this formula we only need to change the frequency of the power supply, the rotating magnetic field speed of the motor stator will change, so that the speed of the motor stator also follows Variety. In this way, the purpose of speed regulation is achieved. So we can regard the frequency converter as a device that changes the power frequency of the motor. In this inverter, first it converts our 50HZ AC power into DC power, and then changes the DC power into AC power with adjustable frequency and voltage through the inverter link in the inverter, and then supplies the three-phase asynchronous motor.

The motor realizes the adjustment of the speed according to the frequency set by us, which can achieve the purpose of stepless speed regulation in a very wide frequency range. There are several ways of frequency converter speed regulation. The main method of frequency conversion speed regulation is that we set the frequency command for the frequency converter. The most commonly used setting of this frequency command can generally be set through the operation panel of the frequency converter. Frequency command, pulse signal setting, 0 to 10V voltage analog signal setting or 0 to 24 mA analog current signal setting, communication mode setting and contact signal setting, etc.


The speed adjustment of the spindle motor in the CNC lathe is adjusted by the analog quantity given. The analog quantity terminal of the frequency converter is the voltage signal taken from the CNC system. This voltage signal is operated by us through the CNC system The rotation speed command issued by the panel then outputs the corresponding analog voltage after passing through the D/A conversion module in the numerical control system. This analog voltage is generally 0V to 10V, which corresponds to the lowest and highest speed of the numerical control system.

The first step of setting the external analog speed control of the inverter, we need to press the PU/EXT key to switch the operation mode to the operation panel (PU) mode. In the second step, we turn the M knob to adjust the inverter parameters to Pr.79, and then press the SET button, the current set value "0" will be displayed, which is the initial value. The third step is to turn the M knob to change the set value to 2. It is an external operation mode. Only when an external signal is given to the inverter, it will operate and start, and then press the SET button. Through the above three steps, you can set the frequency of the external voltage analog signal to control the inverter. Since the CNC lathe uses an ordinary three-phase asynchronous motor, when setting the highest frequency, generally 10V corresponds to 50HZ, and 0V corresponds to the minimum speed. The frequency is fine, it does not have to reach 0HZ.

If we want to change the maximum frequency of the inverter, we only need to set the parameter Pr.125 of the frequency setting gain to the desired maximum frequency. For example, if we want to set the maximum frequency to 45HZ, we will first be in the parameter mode Rotate the M knob, find the parameter Pr.125 and press the set key (SET). At this time, the operation panel of the inverter will display the current highest frequency, such as 50HZ. Then we turn the knob M to adjust 50HZ to 45HZ. Press the SET button to change the maximum frequency to 45HZ. When the numerical control system outputs an analog quantity of 10V, the maximum frequency of the inverter will run at 45HZ. I know a method for setting the frequency of the frequency converter in a CNC lathe. We can roughly understand that if you want to be proficient in setting the frequency converter, you must master some setting methods of the frequency converter parameters. Then the other frequency conversion speed control methods of the frequency converter are also mainly It is through the operation panel to cooperate with some parameters to achieve the purpose of motor speed control. My suggestion is that friends who use the inverter should have a manual for the inverter. You can find various parameters in the manual. It is very helpful for us to quickly grasp how to adjust the speed of the inverter.