1, acceleration and deceleration time

Acceleration time is the time it takes for the output frequency to rise from 0 to the maximum frequency. Deceleration time refers to the time required to fall from 0 to the maximum frequency. Usually use the frequency set signal rise and fall to determine the acceleration and deceleration time. When the motor accelerates, the rate of increase of the frequency setting must be limited so as to prevent overcurrent. In the case of deceleration, the rate of decrease is limited to prevent overvoltage.

Acceleration time setting requirements: the acceleration current is limited to below the inverter overcurrent capacity, not to over-current stall caused by the inverter trip; deceleration time set points are: to prevent the smooth circuit voltage is too large, Trip the frequency converter. Acceleration and deceleration time can be calculated according to the load, but often taken in the commissioning by load and experience to set a longer acceleration and deceleration time, by starting and stopping the motor to observe whether over-current, over-voltage alarm; and then set the acceleration and deceleration gradually Shorten the operation in the principle of alarm does not occur, repeated several times, you can determine the best acceleration and deceleration time.

2, torque increase

Also known as torque compensation, is to compensate for the motor stator winding resistance caused by low speed torque reduction, while the low frequency range f / V method. When set to Auto, the voltage during acceleration can be automatically increased to compensate for the starting torque, so that the motor accelerates smoothly. Such as the use of manual compensation, according to the load characteristics, especially the starting characteristics of the load, through the test can choose a better curve. For variable torque load, such as improper choice will appear at low speed when the output voltage is too high, and the phenomenon of wasted power, and even the motor with a load when the current is large, but the speed does not go to the phenomenon.

3, electronic thermal overload protection

This function is set to protect the motor from overheating. It is used to calculate the temperature rise of the motor according to the operating current and frequency of the CPU in the inverter so as to overheat protection. This function is only suitable for “one to one” occasions, and in “a drag more”, you should install thermal relay on each motor.

Electronic thermal protection setting value (%) = [Motor rated current (A) / Inverter rated output current (A) “× 100%.

4, the frequency limit

That is, the output frequency of the inverter, the lower limit amplitude. Frequency limit is to prevent misoperation or external frequency setting signal source failure, which caused the output frequency is too high or too low, in order to prevent damage to the device a protection function. In the application according to the actual situation can be set. This function can also be used for speed limit, such as belt conveyor, due to the delivery of material is not too much, in order to reduce the wear and tear of machinery and belts, drive can be used, and inverter frequency limit is set to a certain frequency value , So that the belt conveyor can run at a fixed, lower working speed.

5, offset frequency

Some also called deviation frequency or frequency deviation setting. Its purpose is when the frequency is set by an external analog signal (voltage or current), you can use this function to adjust the output frequency when the frequency setting signal is the lowest, as shown in Figure 1. In some frequency inverters, when the frequency setting signal is 0%, the deviation value can be within the range of 0 ~ fmax. Some inverters (such as Ming Shushe and Sanken) can also set the bias polarity. For example, during debugging, when the frequency setting signal is 0%, the output frequency of the inverter is not 0Hz, but it is xHz, at this time, setting the bias frequency to negative xHz will make the output frequency of the inverter be 0Hz.

5, the frequency setting signal gain

This function is valid only when the external analog signal is used to set the frequency. It is used to make up for the inconsistency between the externally set signal voltage and the voltage in the inverter (+ 10v); at the same time, it is convenient for the analog signal voltage to be set. When setting, when the analog input signal is maximum (such as 10v, 5v or 20mA), find out the percentage of output frequency of f / V graph and set it as the parameter; if the external setting signal is 0 ~ 5v, if the inverter output frequency is 0 ~ 50Hz, the gain signal Set to 200%.

7, torque limit

Can be divided into drive torque limit and brake torque limit two. It is based on the inverter output voltage and current values, calculated by the CPU torque, which can be accelerated and decelerated and run-time impact load recovery characteristics significantly improved. The torque limit function enables automatic acceleration and deceleration control. Assuming that the acceleration / deceleration time is less than the load inertia time, the motor can also be automatically accelerated and decelerated according to the torque setting value.

The drive torque function provides a strong starting torque, which, in steady state operation, controls the motor slip and limits the motor torque to the maximum setting, and when the load torque suddenly increases, or even When the acceleration time is set too short, the inverter will not trip. When the acceleration time is set too short, the motor torque does not exceed the maximum setting. Big driving torque is good for starting, it is better to set it as 80 ~ 100%.

The smaller the setting value of braking torque is, the larger the braking force is. It is suitable for occasions of acceleration and deceleration. For example, over-voltage alarm occurs when the setting value of braking torque is too large. If the brake torque is set to 0%, the total amount of regeneration to the main capacitor will be close to zero, so that the motor can decelerate to stop without tripping without braking resistor when decelerating. However, on some loads, for example, when the braking torque is set to 0%, a short idling phenomenon may occur during deceleration, causing the inverter to start repeatedly and the current fluctuates greatly. In severe cases, the inverter trips and should be noticed.

8, acceleration and deceleration mode selection

Also known as acceleration and deceleration curve selection. General frequency converter has linear, nonlinear and S three kinds of curves, usually choose linear curve; nonlinear curve applies to variable torque load, such as fans, etc .; S curve for constant torque load, the acceleration and deceleration changes more slowly. Set according to the load torque characteristics, select the corresponding curve, but there are exceptions, I debug a booster fan inverter, the first choice of non-linear curve of acceleration and deceleration curve, a running inverter to trip, adjust Change many parameters no effect, later changed to S curve after normal. The reason is: before starting fan due to the flue gas flow and self-rotating, and reverse and become a negative load, so choose the S-curve, so that just start the frequency of the slow rise, thus avoiding the inverter Of course, this is the method used for inverters that do not have DC braking enabled.

9, torque vector control

Vector control is based on the theory that: Asynchronous motors and DC motors have the same torque generation mechanism. The vector control method is to decompose the stator current into the specified magnetic field current and torque current, and control them separately. At the same time, the synthesized stator current is output to the motor. Therefore, in principle, the same control performance as the DC motor can be obtained. With torque vector control, the motor can output maximum torque under all operating conditions, especially when the motor is operating at low speed.

At present, almost all inverters use feedbackless vector control. Since the inverters can make slip compensation according to the magnitude and phase of the load current, the motor has very hard mechanical properties and has been able to meet the requirements for most occasions without the need of the inverter External set speed feedback circuit. This feature set, according to the actual situation in the effective and ineffective to choose one.

The function related to this is slip compensation control. Its function is to compensate the speed deviation caused by the fluctuation of the load, and add the slip frequency corresponding to the load current. This function is mainly used for positioning control.

10, energy-saving control

Both the fan and the pump belong to the reduced torque load, that is, as the speed decreases, the load torque decreases in proportion to the square of the speed, while the inverter with energy saving control has a dedicated V / f mode, which can be improved Motor and inverter efficiency, which can automatically reduce the inverter output voltage load current, so as to achieve energy-saving purposes, depending on the circumstances set to be valid or invalid.

To note is that nine, ten these two parameters is very advanced, but some users in the transformation of the equipment, simply can not enable these two parameters, that is, after the opening of frequent inverter trips, disabled after all normal. The reasons are:

(1) the original motor parameters and drive requirements with the use of motor parameters vary greatly.

(2) The function of setting parameters is not enough, for example, the energy saving control function can only be used in the V / f control mode and can not be used in the vector control mode.

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

Leave a Reply

Your email address will not be published. Required fields are marked *