Inventory of Common Parameters of Air Compressor Frequency Converter
There are many setting parameters for air compressor inverters, and each parameter has a certain range of selection. In the application, it is often encountered that the air compressor inverter cannot work normally due to improper setting of a single parameter. Therefore, it is necessary to The relevant parameters are set accurately. Therefore, if you want to save energy, it is impossible not to understand these parameters of the air compressor inverter!
1. Control method
That is, speed control, torque control, PID control or other methods. After the control method is adopted, static or dynamic identification is usually carried out according to the control accuracy.
2. Minimum operating frequency
That is, the minimum speed at which the motor works. When the motor works at a low speed, its heat dissipation performance is very poor. If the motor works at a low speed for a long time, it will cause the motor to burn out. And at low speed, the current in the cable will also increase, which will also cause the cable to heat up.
3. Maximum operating frequency
The maximum frequency of the general air compressor inverter is 60Hz, and some even reach 400Hz. The high frequency will make the motor work at high speed. For ordinary motors, the bearings cannot work at super rated speed for a long time. Whether the rotor of the motor can accept such centrifugal force.
4. Carrier frequency
The higher the carrier frequency is set, the greater the weight of high-order harmonics, which is closely related to factors such as the length of the cable, the heating of the motor, the heating of the cable, the heating of the air compressor, and the inverter.
5. Motor parameters
The air compressor inverter sets the power, current, voltage, speed, and maximum frequency of the motor in the parameters, and these parameters can be directly obtained from the motor nameplate.
6. Frequency hopping
At a certain frequency point, resonance may occur, especially when the overall device is relatively high; when controlling the compressor, avoid the surge point of the compressor.
7. Acceleration and deceleration time
The acceleration time is the time required for the output frequency to rise from 0 to the maximum frequency, and the deceleration time is the time required for the output frequency to drop from the maximum frequency to 0. Usually, the acceleration and deceleration time is judged by the frequency setting signal rising and falling. When the motor is accelerating, the rate of increase of the frequency setting must be restricted to avoid overcurrent, and when the motor is decelerating, the rate of decrease must be restricted to avoid overvoltage.
Acceleration time setting requirements: limit the acceleration current below the overcurrent capacity of the air compressor inverter, so as not to cause the air compressor inverter to trip due to overcurrent stall; the key to setting the deceleration time is to avoid excessive voltage in the lubrication circuit, Stall the regeneration overvoltage and trip the frequency converter of the air compressor. The acceleration and deceleration time can be calculated according to the load, but in the debugging, it is often adopted to set a longer acceleration and deceleration time according to the load and experience first, and observe whether there is an over-current or over-voltage alarm by starting and stopping the motor; then gradually set the acceleration and deceleration time For shortening, the best acceleration and deceleration time can be determined by repeating the operation several times based on the principle that no alarm occurs during the operation.
8. Increased torque
Also called torque compensation, it is a method of increasing the low frequency range f/V to compensate for the torque drop at low speed caused by the motor stator winding resistance. When set to active, the voltage during acceleration can be actively increased to compensate for the starting torque, so that the motor can accelerate smoothly. If manual compensation is selected, according to the load characteristics, especially the starting characteristics of the load, a better curve can be obtained through experiments. For variable torque loads, if the selection is improper, the output voltage at low speed will be too high, which will waste electric energy, and even the current will be large when the motor starts with load, but the speed will not increase.
9. Electronic thermal overload protection
This function is set to protect the motor from overheating. The CPU in the frequency converter of the air compressor calculates the temperature rise of the motor based on the operating current value and frequency, and then performs overheating protection. This function is only applicable to the occasion of “one drive for one”, and for “one drive for many”, a thermal relay should be installed on each motor.
Electronic thermal maintenance setting value (%)=[additional motor current (A)/additional output current of air compressor inverter (A)]×100%.
10. Frequency constraints
That is, the upper and lower limit amplitudes of the output frequency of the air compressor inverter. Frequency limit is a protection function to prevent the output frequency from being too high or too low due to misoperation or failure of the external frequency setting signal source, so as to prevent damage to the equipment. It can be set according to the actual situation in the application. This function can also be used as a speed limiter. For example, if there is a belt conveyor, since there are not too many materials to be transported, in order to reduce the wear of the machine and the belt, the air compressor inverter can be used to drive, and the upper limit frequency of the air compressor inverter can be set. Set it to a certain frequency value, so that the belt conveyor can be operated at a fixed, lower operating speed.
11. Bias frequency
Some are also called error frequency or frequency error setting. Its purpose is that when the frequency is set by an external analog signal (voltage or current), this function can be used to adjust the level of the output frequency when the frequency setting signal is the lowest. When the frequency setting signal of some air compressor inverters is 0%, the error value can be applied within the range of 0~fmax, and some air compressor inverters (such as Mingdianshe, Sanken) can also adjust the bias pole sex to set. For example, when the frequency setting signal is 0% during debugging, the output frequency of the air compressor inverter is not 0Hz, but xHz, then at this moment, set the bias frequency to negative xHz to make the output frequency of the air compressor inverter The frequency is 0Hz.
12. Frequency setting signal gain
This function is only available when the frequency is set by an external analog signal. It is used to compensate the inconsistency between the external setting signal voltage and the internal voltage (+10v) of the air compressor inverter; it is convenient for the selection of the analog setting signal voltage. 5v or 20mA), find out the frequency percentage that can output the f/V graph and set it as a parameter; if the external setting signal is 0~5v, if the output frequency of the air compressor inverter is 0~50Hz , then set the gain signal to 200%.
13. Torque constraint
It can be two kinds of driving torque constraints and braking torque constraints. It is based on the output voltage and current value of the frequency converter of the air compressor, and the torque is calculated by the CPU, which can significantly improve the recovery characteristics of the impact load during acceleration and deceleration and constant speed operation. The torque limiting function enables automatic acceleration and deceleration control. Assuming that the acceleration and deceleration time is less than the load inertia time, it can also ensure that the motor automatically accelerates and decelerates according to the torque setting value.
The drive torque function provides a strong starting torque. In steady state operation, the torque function will control the motor slip and limit the motor torque within the maximum set value. When the load torque suddenly increases, even When the acceleration time is set too short, it will not cause the inverter of the air compressor to trip. When the acceleration time is set too short, the motor torque will not exceed the maximum set value. A large driving torque is beneficial to starting, and it is appropriate to set it at 80-100%.
The smaller the value of the braking torque is, the greater the braking force is, which is suitable for rapid acceleration and deceleration. If the value of the braking torque is set too high, an overvoltage alarm will occur. If the braking torque is set to 0%, the total amount of regeneration added to the main capacitor can be close to 0, so that when the motor is decelerating, it can decelerate to stop without using a braking resistor without tripping. However, on some loads, if the braking torque is set to 0%, there will be a short idling phenomenon during deceleration, causing the air compressor frequency converter to start repeatedly, and the current fluctuates greatly. In severe cases, the air compressor frequency conversion will occur. If the device trips, special attention should be paid.
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