Parameter setting steps of vector converter
Due to the different functions of each type of frequency converter, the names of the same function parameters are not consistent. For the convenience of description, this paper takes the basic parameter names of a frequency converter as an example. Because the basic parameters are almost all types of inverter, it can be done by analogy.
1、 Acceleration and deceleration time
The acceleration time is the time required for the output frequency to rise from 0 to large frequency, and the deceleration time is the time required for the output frequency to fall from large frequency to 0. The acceleration and deceleration time is usually determined by the rise and fall of frequency setting signal. When the motor accelerates, it is necessary to limit the rising rate of frequency setting to prevent over-current, and when the motor decelerates, it is necessary to limit the falling rate to prevent over-voltage.
Setting requirements of acceleration time: the acceleration current shall be limited below the over-current capacity of the frequency converter, and the over-current stall shall not cause the frequency converter trip; The key points of deceleration time setting are: to prevent the voltage of smooth circuit from being too large, and to prevent the regeneration overvoltage from stalling and tripping the frequency converter. The acceleration and deceleration time can be calculated according to the load, but in debugging, a longer acceleration and deceleration time is usually set according to the load and experience, and the over-current and over-voltage alarms are observed by starting and stopping the motor; Then, the set time of acceleration and deceleration is gradually shortened. Based on the principle of no alarm during operation, the good acceleration and deceleration time can be determined by repeated operation for several times.
2、 Torque increase
Also known as torque compensation, is to compensate for the motor stator winding resistance caused by low-speed torque reduction, and increase the low frequency range f / V method. When it is set to automatic, the voltage during acceleration can be raised automatically to compensate the starting torque, so that the motor can accelerate smoothly. If manual compensation is adopted, the 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, and the phenomenon of waste of electric energy will appear. Even when the motor starts with load, the current will be large, and the speed will not go up.
3、 Electronic thermal overload protection
This function is set to protect the motor from overheating. The CPU in the inverter calculates the temperature rise of the motor according to the running current value and frequency, so as to protect the motor from overheating. This function is only applicable to the situation of “one driving one”, while in the case of “one driving more”, the thermal relay should be installed on each motor.
Setting value of electronic thermal protection (%) = [motor rated current (a) / inverter rated output current (a)] × 100%。
4、 Frequency limit
That is, the upper and lower limits of the inverter output frequency amplitude. Frequency limit is a kind of protection function to prevent the output frequency from being too high or too low due to misoperation or external frequency setting signal source failure, 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 for speed limiting. For example, some belt conveyors can be driven by frequency converter in order to reduce the wear of machinery and belt because there are not too many materials to be transported, and the upper limit frequency of frequency converter can be set to a certain frequency value, so that the belt conveyor can run at a fixed and low working speed
5、 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), as shown in Figure 1. When the frequency setting signal of some inverters is 0%, the deviation value can act in the range of 0 ~ Fmax, and some inverters (such as mingdianshe and Sanken) can also set the bias polarity. If in debugging, when the frequency setting signal is 0%, the output frequency of frequency converter is not 0Hz, but XHZ, then the output frequency of frequency converter can be 0Hz by setting the bias frequency to negative XHZ.
6、 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 inverter; At the same time, it is convenient to select the analog setting signal voltage. When the analog input signal is large (such as 10V, 5V or 20mA), the frequency percentage of the output f / V graph can be calculated and set as a parameter; If the external setting signal is 0 ~ 5V, if the inverter output frequency is 0 ~ 50Hz, then set the gain signal to 200%.
7、 Torque limit
It can be divided into driving torque limit and braking torque limit. According to the output voltage and current of the inverter, 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 can realize automatic acceleration and deceleration control. Assuming that the acceleration and deceleration time is less than the load inertia time, the motor can also accelerate and decelerate automatically according to the torque setting value.
The driving torque function provides a powerful starting torque. In steady-state operation, the torque function will control the motor slip and limit the motor torque to a large set value. When the load torque suddenly increases, even if the acceleration time is set too short, the inverter will not trip. When the acceleration time is set too short, the motor torque will not be too large. Large driving torque is good for starting, and 80-100% is better.
The smaller the setting value of braking torque is, the greater the braking force is. It is suitable for the occasions of rapid acceleration and deceleration. For example, if the setting value of braking torque is too high, 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 using the braking resistor and will not trip. However, on some loads, if the braking torque is set to 0%, there will be a short idling phenomenon during deceleration, which will cause the frequency converter to start repeatedly and the current fluctuates greatly. In serious cases, the frequency converter will trip, which should be paid attention to.
8、 Acceleration and deceleration mode selection
Also called acceleration and deceleration curve selection. Generally, there are three kinds of curves: linear curve, nonlinear curve and S curve; Nonlinear curves are suitable for variable torque loads, such as fans; S curve is suitable for constant torque load, and its acceleration and deceleration change slowly. When setting, the corresponding curve can be selected according to the load torque characteristics, but there are also exceptions. When debugging the inverter of a boiler induced draft fan, the author first selects the non-linear curve for the acceleration and deceleration curve, and the inverter trips when it runs together. It is ineffective to adjust and change many parameters, and then it is normal after changing to S curve. The reason is: before starting, the induced draft fan rotates automatically due to the flue gas flow, and reverses to become a negative load, so the S curve is selected, so that the rising speed of frequency is slow when starting, 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.
Application of vector transducer
On the premise of no negative impact on the normal use of escalator, the concept of vector variable frequency speed regulation is introduced. That is, according to the signal generated by the sensor, when someone is riding, the escalator runs at the original speed (50 Hz); When there is no one, the escalator will slow down to low speed or stop running.
The system requires the frequency converter to start and run smoothly, with good acceleration performance, large starting torque and strong overload capacity. At the same time, when the frequency converter speed control system fails, the control system will automatically switch to the power frequency operation to ensure the normal implementation of the escalator conveying function.
For the passenger escalator, the peak time of use generally appears in the afternoon and evening, and the utilization rate of the rest of the time is low, which has considerable energy-saving space. According to the above transformation principles, considering the investment cost and automation level, the following variable frequency drive scheme is proposed:
·Saj-8000g frequency converter is used to drive the elevator host. The frequency converter adopts multi speed control mode, and two operating frequencies are set: main frequency (low speed) and multi speed frequency 1 (high speed);
·An infrared sensor switch is installed at each end of the elevator. When passengers pass through the elevator, the infrared sensor switch is triggered and sends a switch signal to the frequency converter;
·When there is passenger flow, the infrared sensor switch is triggered, and the frequency converter immediately accelerates to multi speed frequency 2, which makes the elevator run at high speed;
·When the elevator is running at high speed, the built-in timer of the frequency converter starts timing. If no more passengers pass the elevator during the timing period, the frequency converter will automatically switch to multi speed frequency 1 for low-speed operation after timing;
·If a passenger triggers the photoelectric switch again during the timer, the timer will time again;
·For the elevator up and down, the peripheral control adopts switch interlock to ensure the normal operation of the elevator system;
·In order to consume the surplus energy generated in the downward or braking process, it is necessary to install a braking resistor on the frequency converter.
The elevator host driven by tri crystal vector universal inverter can not only meet the requirements of smooth start-up, large starting torque, strong overload capacity and high speed regulation accuracy of the system; And the motor drive by frequency conversion can reduce mechanical wear, prolong service life, and work more safely and reliably. Because of the large space to adjust the motor speed, the energy-saving effect of the system is more significant.
Editor in charge: yyx