The supplier of the frequency converter braking unit reminds you that there are many setting parameters for the frequency converter, and each parameter has a certain selection range. During use, it is common to encounter the phenomenon of the frequency converter not working properly due to improper setting of individual parameters. Therefore, it is necessary to correctly set the relevant parameters.
1. Control method:
That is, speed control, torque control, PID control, or other methods. After adopting the control method, it is generally necessary to perform static or dynamic identification based on the control accuracy.
2. Minimum operating frequency:
The minimum speed at which the motor operates. When the motor operates at low speeds, its heat dissipation performance is poor, and prolonged operation at low speeds can cause the motor to burn out. Moreover, at low speeds, the current in the cable will also increase, which can cause the cable to heat up.
3. Maximum operating frequency:
The maximum frequency of a typical frequency converter is up to 60Hz, and some even up to 400Hz. High frequencies will cause the motor to run at high speeds. For ordinary motors, their bearings cannot operate at their rated speed for a long time. Can the rotor of the motor withstand such centrifugal force.
4. Carrier frequency:
The higher the carrier frequency is set, the larger the high-order harmonic components, which is closely related to factors such as cable length, motor heating, cable heating, and frequency converter heating.
5. Motor parameters:
The frequency converter sets the power, current, voltage, speed, and maximum frequency of the motor in the parameters, which can be directly obtained from the motor nameplate.
6. Frequency hopping:
At a certain frequency point, resonance may occur, especially when the entire device is relatively high; When controlling the compressor, avoid the surge point of the compressor.
7. Acceleration and deceleration time
Acceleration time refers to the time required for the output frequency to rise from 0 to the maximum frequency, while deceleration time refers to the time required for the output frequency to fall from the maximum frequency to 0. Usually, the acceleration and deceleration time is determined by the frequency setting signal rising and falling. During motor acceleration, the rate of increase in frequency setting must be limited to prevent overcurrent, and during deceleration, the rate of decrease must be limited to prevent overvoltage.
Acceleration time setting requirements: Limit the acceleration current to below the overcurrent capacity of the frequency converter, so as not to cause the frequency converter to trip due to overcurrent stall; The key points for setting deceleration time are to prevent the smoothing circuit voltage from being too high, and to prevent the regeneration overvoltage from stalling and causing the frequency converter to trip. The acceleration and deceleration time can be calculated based on the load, but in debugging, it is common to set a longer acceleration and deceleration time based on the load and experience, and observe whether there are overcurrent and overvoltage alarms by starting and stopping the motor; Then gradually shorten the acceleration and deceleration setting time, based on the principle of no alarm during operation, and repeat the operation several times to determine the optimal acceleration and deceleration time.
8. Torque Enhancement
Also known as torque compensation, it is a method of increasing the low-frequency range f/V to compensate for the decrease in torque at low speeds caused by the resistance of the motor stator winding. When set to automatic, the voltage during acceleration can be automatically increased to compensate for the starting torque, allowing the motor to accelerate smoothly. When using manual compensation, the optimal curve can be selected through testing based on the load characteristics, especially the starting characteristics of the load. For variable torque loads, improper selection can result in high output voltage at low speeds, wasting electrical energy, and even causing high current when starting the motor with a load without increasing the speed.
9. Electronic thermal overload protection
This function is designed to protect the motor from overheating. It calculates the temperature rise of the motor based on the operating current value and frequency by the CPU inside the frequency converter, thereby providing overheating protection. This function is only applicable to "one to one" situations, and in "one to many" situations, thermal relays should be installed on each motor.
Electronic thermal protection setting value (%)=[rated current of motor (A)/rated output current of frequency converter (A)] × 100%.
10. Frequency limitation
The upper and lower limit amplitudes of the output frequency of the frequency converter. Frequency limitation is a protective function that prevents misoperation or external frequency setting signal source failure, which can cause the output frequency to be too high or too low, in order to prevent damage to the equipment. Set according to the actual situation in the application. This function can also be used as a speed limit. For some belt conveyors, due to the limited amount of material being conveyed, a frequency converter can be used to reduce mechanical and belt wear. The upper limit frequency of the frequency converter can be set to a certain frequency value, so that the belt conveyor can operate at a fixed and lower working speed.
11. Bias frequency
Some are also called deviation frequency or frequency deviation setting. Its purpose is to adjust the output frequency when the frequency is set by an external analog signal (voltage or current), using this function to set the lowest output frequency of the frequency setting signal. Some frequency converters can operate within the range of 0-fmax when the frequency setting signal is 0%, and some frequency converters (such as Mingdian and Sanken) can also set the bias polarity. If during debugging, when the frequency setting signal is 0%, the output frequency of the frequency converter is not 0Hz but xHz, then setting the bias frequency to negative xHz can make the output frequency of the frequency converter 0Hz.
12. Frequency setting signal gain
This function is only effective when setting the frequency with an external analog signal. It is used to compensate for the inconsistency between the external set signal voltage and the internal voltage (+10v) of the frequency converter; At the same time, it is convenient to simulate the selection of signal voltage settings. When setting, when the analog input signal is at its maximum (such as 10v, 5v, or 20mA), calculate the frequency percentage that can output f/V graphics and use it as a parameter for setting; If the external setting signal is 0-5V and the output frequency of the frequency converter is 0-50Hz, then the gain signal can be set to 200%.
13. Torque limit
It can be divided into two types: driving torque limitation and braking torque limitation. It calculates torque through the CPU based on the output voltage and current values of the frequency converter, which can significantly improve the recovery characteristics of impact loads during acceleration, deceleration, and constant speed operation. The torque limiting function can achieve 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 driving torque function provides powerful starting torque. During steady-state operation, the torque function controls the motor slip and limits the motor torque to 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 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 for starting, so it is more appropriate to set it at 80-100%.
The smaller the set value of the braking torque, the greater the braking force, which is suitable for situations of rapid acceleration and deceleration. If the set value of the braking torque is too high, an overvoltage alarm phenomenon may occur. If the braking torque is set to 0%, it can make the total amount of regeneration added to the main capacitor close to 0, so that the motor can decelerate to a stop without using a braking resistor and will not trip. But on some loads, such as when the braking torque is set to 0%, there may be a brief idling phenomenon during deceleration, causing the frequency converter to repeatedly start and the current to fluctuate greatly. In severe cases, it may trip the frequency converter, which should be taken seriously.