Several of the adjustment technical parameters of the inverter you need to know

- Aug 26, 2019-

The inverter function parameters are many, generally there are dozens or even hundreds of parameters for the user to choose. In practical application, there is no need to set and debug each parameter, most of them as long as the factory set value can be. However, some parameters, because they have a lot to do with actual usage, and some of them are related to each other, are set and debugged according to the actual situation.

1. Acceleration or deceleration time

Acceleration time is the time it takes for the output frequency to rise from 0 to the maximum frequency, and the deceleration time is the time it takes to drop from the maximum frequency to 0. The frequency is usually used to set the signal to rise and fall to determine the time of increase and deceleration. The increase rate set by the frequency must be limited when the motor accelerates to prevent overcurrent, and the drop rate to prevent overvoltage when decelerating.

Acceleration time setting requirements: the acceleration current is limited to the drive over current capacity, do not cause the over-loss speed to cause the inverter tripping; The deceleration time can be calculated according to the load, but in debugging often take the load and experience first set a longer deceleration time, through the start ingress and stop motor to observe whether there is an overcurrent, overvoltage alarm, and then the deceleration setting time gradually shortened, in operation does not occur alarm as the principle, repeated several times, you can determine the best deceleration time.

2. Torque lift

Also known as torque compensation, is a method to compensate for the reduction of torque at low speed caused by the resistance of the motor stator winding, and to increase the low frequency range f/V. When set to automatic, the voltage at acceleration can be automatically raised to compensate for the starting torque, so that the motor accelerates smoothly. If manual compensation is used, a better curve can be selected by test according to the load characteristics, especially the starting characteristics of the load. For torque load, such as improper selection will appear at low speed when the output voltage is too high, and waste of electrical energy phenomenon, there may even be the motor load start ingress with the current, and the speed can not go up the phenomenon.

3. Electronic thermal overload protection

This function is set to protect the motor from overheating, it is the CPU in the inverter according to the operating current value and frequency to calculate the temperature rise of the motor, so as to protect the overheating. This function is only applicable to "one drag one" occasion, and in the "one drag many" occasions, should be installed on each motor heat relay.

Electronic thermal protection settings (%) =motor rated current (A)/inverter rated output current (A) >x 100%.

4. Frequency limits

That is, the upper and lower amplitude slots of the output frequency of the drive. Frequency limits are a protection function that prevents the device from being misoperated or the outlet frequency set signal source is faulty and causes the output frequency to be too high or too low. Set in the application as it is. This function can also be used for speed limit, if some belt conveyor, because the transport material is not too much, in order to reduce the wear of machinery and belt, can be driven by the inverter, and the upper frequency of the inverter is set to a certain frequency value, so that the belt conveyor can run on a fixed, low operating speed.

5. Bias frequency

Some are also called deviation frequency or frequency deviation settings. The purpose is to adjust the output frequency of the lowest output frequency when the frequency is set by an external analog signal (voltage or current), as shown in Figure 1. Some inverters when the frequency setting signal is 0%, the deviation value can act in the range of 0 to fmax, and some inverters (such as bright electric houses, three reclamations) can also be set for bias polarity. If, in commissioning, when the frequency setting signal is 0%, the frequency output frequency of the drive is not 0Hz, but xHz, then the bias frequency is set to negative xHz can make the frequency of the drive output at 0Hz.

6. Frequency setting signal gain

This function is only valid when setting the frequency with an external analog signal. It is used to compensate for the inconsistency between the external set-up signal voltage and the voltage within the inverter (10v), and at the same time facilitates the selection of the set signal voltage, when the analog input signal is the maximum (e.g. 10v, 5v or 20mA), to find out the frequency percentage that can be output f/V graphics and set as a parameter. If the external set signal is 0 to 5v, if the output frequency of the drive is 0 to 50Hz, the gain signal can be set to 200%.

7. Torque limit

It can be divided into two types: drive torque limit and brake torque limit. It is based on the output voltage and current values of the drive, and the torque calculation by the CPU can significantly improve the impact load recovery characteristics of the acceleration and deceleration and constant speed operation. The torque limit function enables automatic acceleration and deceleration control. It is also assumed that the reduction time is less than the load inertia time, the motor can also be automatically accelerated and decelerated according to the torque setting.

The drive torque function provides a powerful starting torque, the torque function will control the motor differential when running in a steady state, while limiting the motor torque to the maximum set value, and when the load torque suddenly increases, it does not cause the inverter tripping even when the acceleration time is set too short. The motor torque does not exceed the maximum setting when the acceleration time is set too short. The drive torque is favorable to the start, so that it is set to 80 to 100%.

The smaller the brake torque setting value, the greater its braking power, suitable for the rapid deceleration of the occasion, such as the brake torque setting value set over the General Assembly has a pressure alarm phenomenon. If the brake torque is set to 0%, the total amount of regeneration added to the main capacitor is close to 0, so that the motor can also slow down without the brake resistor to stop and not trip when the motor slows down. However, on some loads, such as brake torque is set to 0%, when the deceleration will appear a short-term idling phenomenon, resulting in the inverter repeated start, the current fluctuates significantly, in severe cases will cause the inverter tripping, should be noted.

8. Add deceleration mode selection

Also called the retarding curve selection. The general inverter has three linear, nonlinear and S curves, which are usually mostly linear, nonlinear curves are suitable for torque loads, such as fans, etc., and S curves are suitable for constant torque loads, which are slow to reduce. Set according to the load torque characteristics, choose the corresponding curve, but there are exceptions, the author in debugging a boiler fan inverter, the first will add the deceleration curve to select nonlinear curve, one start the transfer of the transition frequency on the trip, adjustment and change many parameters have no effect, after changing to S curve after normal. The reason is: the front-of-the-run fan because of the flue flue flue flow and self-rotation, and reverse and become a negative load, so that the S curve, so that the frequency rise speed of the first start is slow, thus avoiding the occurrence of the frequency shuttle tripping, of course, this is for the dc brake function is not started by the drive method used.

9. Torque vector control

Vector control is based on the theory that asynchronous motors have the same torque generation mechanism as DC motors. Vector control is to break down the stator current into the specified magnetic field current and torque current, respectively, to control, and the two synthesis of the stator current output to the motor. Therefore, the same control performance as the DC motor can be obtained in principle. With torque vector control, the motor can output the maximum torque under various operating conditions, especially in the low-speed operating area.

Now almost all of the inverters use no feedback vector control, because the inverter can be based on the load current size and phase of the differential compensation, so that the motor has very hard mechanical characteristics, for most occasions has been able to meet the requirements, do not need to set up the speed feedback circuit outside the inverter.

The setting of this function can be selected in a valid and invalid basis according to the actual situation. The related function is the differential compensation control, which is used to compensate for the speed deviation caused by load fluctuations, and can be added to the differential frequency corresponding to the load current. This function is primarily used for positioning control.

10. Energy-saving control

Fans and pumps belong to the torque reduction load, that is, with the decrease of speed, the load torque and the square of the speed to reduce, and the inverter with energy-saving control function design has a special V/f mode, this mode can improve the efficiency of the motor and inverter, which can automatically reduce the output voltage of the inverter according to the load current, so as to achieve energy-saving purposes, It can be set to valid or invalid depending on the situation.

To illustrate that the nine, ten of these two parameters are very advanced, but there are some users in the equipment transformation, it is not possible to enable these two parameters, that is, after the activation of the frequency shuttle tripping frequently, after the deactivation of everything is normal. The reasons are: (1) the original motor parameters and the inverter requirements of the motor parameters are too different. (2) The function of setting parameters is not enough, such as energy saving control function can only be used in V/f control mode, can not be used in vector control mode. (3) Vector control is enabled, but no manual setting and automatic reading of motor parameters is carried out, or the reading method is not correct.