There are many parameters of the frequency converter, each parameter has a certain range of choice, often encountered in use due to the improper setting of individual parameters, resulting in the frequency converter can not work properly. Therefore, the frequency converter debugging is from the correct settings of the parameters of the inverter to start. This paper summarizes 16 basic methods of frequency converter parameter setting, which can be used for reference and correct setting of relevant parameters.
1. Control
That is, speed control, pitch control, PID control or other means. After adopting the control mode, the static or dynamic identification should be carried out according to the control precision.
2. Minimum operating frequency
That is, the minimum speed of the motor running, the motor at low speed, its poor heat dissipation performance, motor running for a long time at low speed, will lead to motor burning. And at low speed, the current in the cable will also increase, will also lead to cable heating.
3.Maximum operating frequency
General inverter maximum frequency to 60 Hz, and some even to 400 Hz, high frequency will make the motor high-speed operation, which for ordinary motor, its bearing can not long time of excessive rated speed operation, whether the rotor of the motor can bear such centrifugal force.
4.Carrier frequency
The higher the carrier frequency setting, the greater the higher harmonic component, which is closely related to cable length, motor heating, cable heating frequency converter heating and other factors.
5.Motor parameters
The inverter sets the motor's power, current, voltage, speed and maximum frequency in the parameters, which can be obtained directly from the motor nameplate.
6.Frequency hopping
At a certain frequency point, resonance may occur, especially when the whole device is high; in the control of the compressor, to avoid the surge point of the compressor.
7. Acceleration and deceleration time
The 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 for the output frequency to fall from the maximum frequency to 0. Frequency is usually used to set the signal up and down to determine the acceleration and deceleration time. The rate of rise of the frequency setting shall be limited to prevent over-current when the motor is accelerating, and the rate of decline shall be limited to prevent over-voltage when the motor is decelerating.
Acceleration time setting requirements: the acceleration current will be limited to the inverter over-current capacity below, so as not to cause overcurrent stall frequency converter trip; Do not stall the regenerative overvoltage and trip the converter. The acceleration and deceleration time can be calculated according to the load, but in the debugging, the long acceleration and deceleration time is usually set according to the load and experience Then, the setting time of acceleration and deceleration is gradually shortened, and the optimal acceleration and deceleration time can be determined by repeated operation for several times.
8. Torque Boost
Also called torque compensation, is to compensate for motor stator winding resistance caused by low-speed torque reduction, and the low frequency range F/V increase method. When it is set to automatic, the voltage of acceleration can be raised automatically to compensate the starting torque and accelerate the motor 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 variable torque load, such as improper selection will appear when the low-speed output voltage is too high, and the waste of electricity, and even a motor with load when starting current is large, and speed up the phenomenon.
9.Electronic thermal overload protection
This function is set to protect the motor from overheating. It is used to protect the motor from overheating by calculating the temperature rise of the motor according to the operating current value and frequency of the CPU in the inverter. This function only applies to“One drag one” occasion, and in“One drag more”, it should be installed in each motor heat relay. Electronic thermal protection set value (%) = [ motor rated current (a)/inverter rated output current (a)] × 100% .
10.Frequency limit
That is, the upper and lower limits of the frequency converter output amplitude. Frequency limit is a protection function of setting signal source to prevent misoperation or external frequency from fault, which causes the output frequency to be too high or too low in order to prevent the equipment from being damaged. In the application according to the actual situation can be set. This function can also be used for speed limit, such as some belt conveyor, because the transfer of material is not too much, in order to reduce mechanical and belt wear, can be driven by a frequency converter, and the upper frequency of the frequency converter set to a certain frequency value, this enables the belt conveyor to operate at a fixed, lower speed.
11.Offset frequency
Some are also called deviation frequency or frequency deviation settings. The utility model is used for adjusting the output frequency when the frequency is set by an external analog signal (voltage or current) . When the frequency setting signal is 0% , the deviation value can be applied in the range of 0 ~ fmax, and the bias polarity can be set in some inverters (such as electric house and Sanken) . If the frequency setting signal is 0% in debugging, the frequency of the inverter output is not 0 Hz, but XHZ, then set the bias frequency to negative XHZ can make the frequency of the inverter output to 0 Hz.
12.Frequency set signal gain
This function is only effective when the frequency is set by an external analog signal. It is used to compensate for the inconsistency between the external set signal voltage and the internal voltage of the inverter (+ 10V) , and to facilitate the selection of the analog set signal voltage when the analog input signal is maximum (such as 10V, 5V or 20mA) , the frequency percentage of the F/V figure can be calculated and set as a parameter; if the external setting signal is 0-5V, if the frequency of the inverter output is 0-50Hz, the gain signal can be set to 200% .
13.Torque limit
Can be drive torque limit and brake torque limit two. It is based on the output voltage and current of the inverter, and calculated by the CPU. It can significantly improve the impact load recovery characteristics of acceleration and deceleration and constant speed operation. The torque limit function can realize automatic acceleration and deceleration control. If the acceleration and deceleration time is less than the load inertia time, the motor can be automatically accelerated and decelerated according to the torque set value.
The drive torque function provides a powerful starting torque, which controls the slip of the motor while limiting the motor torque to a maximum set value when the load torque suddenly increases, even in the acceleration time set too short, it will not cause the frequency converter trip. In the acceleration time set too short, the motor torque will not exceed the maximum set value. Large driving torque is beneficial to start, so 80 ~ 100% is better.
The smaller the setting value of braking torque, the greater the braking force, suitable for the occasion of rapid acceleration and deceleration, such as excessive setting of braking torque will appear over-voltage alarm phenomenon. If the brake torque is set to 0% , the regeneration amount added to the main capacitor can be close to 0, so that the motor can be decelerated to stop without using the brake resistance without tripping. But in some loads, such as the braking torque set to 0% , there will be a short idling phenomenon when decelerating, causing the inverter to start repeatedly, the current fluctuates greatly, when serious it will make the inverter trip, should be noted.
14.Choose Acceleration and deceleration modes
Also known as acceleration and deceleration curve selection. The general inverter has three kinds of curves: linear curve, nonlinear curve and S curve, and most of them choose linear curve. The nonlinear curve is suitable for variable torque load, such as fan, etc. . The S curve is suitable for constant torque load, its acceleration and deceleration changes slowly. The corresponding curve can be selected according to the load torque characteristics, but there are some 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, a start-up operation on the trip converter, adjust to change many parameters have no effect, after the s-curve after the normal. The reasons are as follows: the induced draft fan rotates by itself because of the flue gas flow before starting, and reverses to become negative load, thus avoiding the frequency converter trip, of course, this is aimed at the DC brake function of the converter does not start the method used.
15.Torque vector
Control vector control is based on the theory that induction motors and DC motor have the same torque-producing mechanism. Vector control method is to decompose stator current into specified magnetic field current and torque current, and control them respectively, at the same time, the combined stator current is output to the motor. Therefore, in principle, the same control performance as the DC motor can be obtained. With the torque vector control function, the motor can output the maximum torque under various operating conditions, especially in the low-speed operation area.
Now almost all of the frequency converter adopts non-feedback vector control, because the frequency converter can compensate the slip according to the magnitude and phase of the load current, so that the motor has very hard mechanical characteristics, and can meet the requirements for most occasions, there is no need to set the speed feedback circuit outside the inverter. The setting of this function, according to the actual situation in the valid and invalid can choose one.
The related function is slip compensation control, which is used to compensate the speed deviation caused by the 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 controls
The fan and water pump all belong to the load of reducing torque, that is, the load torque decreases in proportion to the square of the rotational speed as the rotational speed decreases, this mode can improve the efficiency of the motor and the inverter, which can automatically reduce the output voltage of the inverter according to the load current, so as to save energy.
It should be explained that the two parameters of electronic thermal overload protection and frequency limitation are very advanced, but some users can not enable these two parameters at all during the equipment transformation, that is, the frequency converter trips frequently after being enabled, everything is normal after discontinuation. The reasons are as follows:
1 the difference between the parameters of the original motor and those required by the frequency converter is too large.
2 insufficient understanding of the function of setting parameters, such as energy-saving control function can only be used in V/F control mode, can not be used in vector control mode. The vector control mode is enabled, but the manual setting and automatic reading of the motor parameters are not carried out, or the reading method is improper.
Source: internet (for study only, intrusion and deletion)
