1. Control mode:

That is, speed control, torque control, PID control or other methods. After the control mode is adopted, the static or dynamic identification is generally carried out according to the control accuracy.

2. Minimum operating frequency:

That is, the minimum speed of the motor. When the motor runs at low speed, its heat dissipation performance is very poor. If the motor runs at low speed for a long time, it will cause the motor to burn out. Moreover, 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 general frequency converters is 60Hz, and some even 400 Hz. High frequency will make the motor run at high speed. For ordinary motors, their bearings cannot run at over rated speed for a long time. Can the rotor of the motor bear such centrifugal force.

4. Carrier frequency:

The higher the carrier frequency is set, the greater the higher the harmonic component, which is closely related to the length of the cable, the heating of the motor, the heating of the cable, the heating of the frequency converter and other factors.

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 whole 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 fall from the maximum frequency to 0. The acceleration and deceleration time is usually determined by the rise and fall of the frequency setting signal. When the motor accelerates, the rising rate of the frequency setting must be limited to prevent overcurrent, and when the motor decelerates, the falling rate must be limited to prevent overvoltage.

Acceleration time setting requirements: limit the acceleration current 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 the deceleration time are to prevent the smoothing circuit voltage from being too large, so as not to make the regeneration overvoltage stall and trip the frequency converter. The acceleration and deceleration time can be calculated according to the load, but in debugging, it is often used to set a long acceleration and deceleration time according to the load and experience, and observe whether there is overcurrent and overvoltage alarm by starting and stopping the motor; Then the acceleration and deceleration setting time is gradually shortened. Based on the principle of no alarm during operation, repeat the operation for several times to determine the best acceleration and deceleration time.

8. Torque increase

Also known as torque compensation, it is a method to increase the low frequency range f/v in order to compensate for the torque reduction at low speed caused by the stator winding resistance of the motor. When set to automatic, the voltage during acceleration can be automatically increased to compensate for the starting torque, so that the motor can accelerate smoothly. If manual compensation is adopted, a better curve can be selected through test according to the load characteristics, especially the starting characteristics of the load. For variable torque load, if it is not selected properly, the output voltage at low speed will be too high, which will waste electric energy. Even when the motor starts with load, the current will be large, but the speed will not go up.

9. Electronic thermal overload protection

This function is set to protect the motor from overheating. The CPU in the frequency converter calculates the temperature rise of the motor according to the operating current value and frequency, so as to protect the motor from overheating. This function is only applicable to the situation of "one driven by one". When "one driven by many", thermal relays should be installed on each motor.

Set value of electronic thermal protection (%) = [rated current of motor (a) / rated output current of frequency converter (a)] × 100% 。

10. Frequency limit

That is, the upper and lower limits of the output frequency of the frequency converter. Frequency limit is a protection function to prevent the output frequency from being too high or too low due to misoperation or the 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 limit. For example, some belt conveyors can be driven by frequency converters in order to reduce the wear of machinery and belts because there are not too many materials to be transported, and the upper limit frequency of the frequency converter can be set to a certain frequency value, so that the belt conveyor can run at a fixed and low 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). When the frequency setting signal of some frequency converters is 0%, the deviation value can act in the range of 0 ~ Fmax. Some frequency converters (such as mingdianshe and Sanken) can also set the bias polarity. If the frequency setting signal is 0% during commissioning, the output frequency of the frequency converter is not 0Hz, but XHZ, then set the bias frequency to negative XHZ to 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 make up 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 select the analog setting signal voltage. When the analog input signal is the maximum (such as 10V, 5V or 20mA), calculate the frequency percentage of the outputable f/v pattern and set it as a parameter; If the external setting signal is 0 ~ 5V, if the output frequency of the frequency converter is 0 ~ 50Hz, set the gain signal to 200%.

13. torque limit

It can be divided into driving torque limit and braking torque limit. According to the output voltage and current value of the frequency converter, the CPU calculates the torque, which can significantly improve the impact load recovery characteristics during acceleration and deceleration and constant speed operation. The torque limiting function can realize 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 powerful starting torque. During steady-state operation, the torque function will control the motor slip and limit the motor torque to the maximum set value. When the load torque suddenly increases, even if 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 setting value. Large driving torque is beneficial to starting, and it is better to set it at 80 ~ 100%.

The smaller the set value of braking torque is, the greater the braking force is, which is suitable for the occasions of rapid acceleration and deceleration. For example, if the set value of braking torque is set too much, the over-voltage alarm will appear. 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 decelerates, it can also decelerate to stop without tripping without using the braking resistance. However, on some loads, such as when the braking torque is set to 0%, there will be a short-term idling phenomenon during deceleration, causing the frequency converter to start repeatedly, the current fluctuates greatly, and the frequency converter will trip in serious cases, which should be paid attention to.

14. Acceleration and deceleration mode selection

Also known as acceleration and deceleration curve selection. Generally, the frequency converter has three kinds of curves: linear curve, nonlinear curve and S curve, and most of them choose linear curve; The nonlinear curve is applicable to variable torque loads, such as fans; S-curve is applicable to constant torque load, and its acceleration and deceleration changes slowly. When setting, the corresponding curve can be selected according to the load torque characteristics, but there are also exceptions. When debugging the frequency converter of a boiler induced draft fan, the author first selects the nonlinear curve for the acceleration and deceleration curve, and the frequency converter will trip when running together. Adjusting and changing many parameters has no effect, and then it will be normal after changing to S curve. The reason is: before starting, the induced draft fan rotates by itself due to the flue gas flow, and reverses to become a negative load. In this way, the S curve is selected, so that the frequency rise speed at the beginning of starting is slow, so as to avoid the occurrence of frequency converter tripping. Of course, this is the method adopted for the frequency converter without starting DC braking function.

15. Torque vector control

Vector control is based on the theory that asynchronous motor and DC motor have the same torque generation mechanism. Vector control method is to decompose the stator current into specified field current and torque current, control them respectively, and output the combined stator current to the motor at the same time. Therefore, the same control performance as DC motor can be obtained in principle. With the torque vector control function, the motor can output the maximum torque under various operating conditions, especially in the low-speed operation area.

Nowadays, almost all frequency converters adopt no feedback vector control. Because the frequency converter can compensate the slip according to the magnitude and phase of the load current, the motor has very hard mechanical characteristics, which can meet the requirements for most occasions, and there is no need to set a speed feedback circuit outside the frequency converter. This function can be set by selecting one of the valid and invalid according to the actual situation.

The related function is slip compensation control, which is used to compensate the speed deviation caused by load fluctuation, and the slip frequency corresponding to the load current can be added. This function is mainly used for positioning control.

16. Energy saving control

Fans and water pumps are torque reducing loads, that is, as the speed decreases, the load torque decreases in proportion to the square of the speed. The frequency converter with energy-saving control function is designed with a special v/f mode, which can improve the efficiency of the motor and frequency converter. It can automatically reduce the output voltage of the frequency converter according to the load current, so as to achieve the purpose of energy saving. It can be set to be effective or invalid according to the specific situation.

It should be noted that the parameters 9 and 10 are very advanced, but some users cannot enable these two parameters at all in the equipment transformation, that is, the frequency converter trips frequently after enabling, and everything is normal after disabling. The reasons are:

(1) The original motor parameters are too different from those required by the frequency converter.

(2) The function of setting parameters is not well understood. For example, the energy-saving control function can only be used in v/f control mode, not in vector control mode.

(3) Vector control mode is enabled, but manual setting and automatic reading of motor parameters are not carried out, or the reading method is improper.