Siemens inverter parameter setting discussion - Database & Sql Blog Articles

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1 Introduction In the past ten years, with the development of large-scale integrated circuits, computer control technology and modern control theory, especially the application of vector control technology, the AC variable frequency speed control technology has gradually provided a wide speed range and high speed. Accuracy, fast dynamic response, and good technical performance in four quadrants for reversible operation, speed regulation characteristics comparable to DC electric drives. In the AC speed regulation technology, the performance of the variable speed speed regulation performance and reliability is constantly improving, and the price is also continuously decreasing, especially its power saving effect is obvious, and it is extremely convenient to realize the AC motor speed regulation. In all occasions where speed control is required, the frequency converter is widely used for its convenient operation, small size and high control performance. Some problems that occur in the use of the inverter, in many cases, are caused by improper settings of the inverter parameters. The Siemens micromaster 440 inverter can set several thousand parameters. Only the system parameters, suitable and accurate settings can make full use of the inverter performance.

2 Control mode selection The selection of the inverter control mode is determined by the torque characteristics of the load. The mechanical load torque characteristics of the motor are determined according to the following relationship:
p= tn/ 9550
Where: p - motor power (kw)
T——torque (n. m)
n——Speed ​​(r/min)
The relationship between the torque t and the number of revolutions n can be roughly classified into three types depending on the type of load.
(1) A constant torque load that does not change much even if the speed varies, such as a conveyor belt, a crane, an extruder, a compressor, and the like.
(2) As the speed decreases, the torque decreases by the square of the speed. Such loads are such as fans, various liquid pumps, and the like.
(3) The higher the speed, the smaller the torque and the smaller the constant power load. Such loads are such as rolling mills, machine tool spindles, coilers, and the like.
The control modes provided by the inverter include v/f control, vector control and torque control. The v/f control has linear v/f control and parabolic characteristic v/f control. Setting the inverter parameter p1300 to 0, the inverter works in linear v/f control mode, which will make the magnetic flux and excitation current at the time of speed regulation basically unchanged. It is suitable for general constant torque speed regulation objects whose working speed is not in the low frequency range.
Set p1300 to 2, the inverter works in parabolic characteristic v/f control mode, which is suitable for fans and pumps. The shaft power n of such a load is approximately proportional to the third power of the rotational speed n. Its torque m is approximately proportional to the square of the rotational speed n. For this kind of load, if the v/f characteristic of the frequency converter is linear, the allowable torque of the motor at a low speed is much larger than the load torque, resulting in a serious drop in power factor and efficiency. In order to meet the needs of such a load, the voltage is reduced in a square relationship as the output frequency is reduced, thereby reducing the magnetic flux and the exciting current of the motor, keeping the power factor within an appropriate range.
The v/f control curve can be further adapted to the load characteristics by setting parameters. Set p1312 to a suitable value between 0 and 250 with start-up boost. The output voltage at low frequencies is appropriately increased with respect to the linear v/f curve to compensate for the problem that the voltage drop caused by the stator resistance at low frequencies causes the motor torque to decrease. Suitable for speed control objects with large starting torque.
When the inverter v/f control mode drives the motor, in some frequency segments, the current and speed of the motor will oscillate. In severe cases, the system cannot run, and even overcurrent protection occurs during the acceleration process, so that the motor cannot start normally. It is more serious when light load or torque inertia is small. The jump point and the jump band width can be set on the v/f curve according to the frequency point at which the system oscillates. When the motor accelerates, these frequency segments can be automatically skipped to ensure the normal operation of the system. Four different jump points can be set from p1091 to p1094, and p1101 is set to determine the jump bandwidth.
Some loads require a specific torque from the motor at a specific frequency, and the desired control curve can be obtained by setting the inverter parameters with programmable v/f control. Set p1320, p1322, p1324 to determine the programmable v/f characteristic frequency coordinates, and the corresponding p1321, p1323, and p1325 are programmable v/f characteristic voltage coordinates.
The parameter p1300 is set to 20 and the inverter works in vector control. This kind of control is relatively perfect, the speed range is wide, the starting torque in the low speed range is high, the precision is up to 0.01%, the response is very fast, and the high-precision speed regulation adopts the svpwm vector control mode.
The parameter p1300 is set to 22 and the inverter operates in vector torque control. This kind of control method is the most advanced control method in the world. The other method is to simulate the parameters of the DC motor, and carry out the control of the conformal transformation. The vector torque control is directly controlled by the parameters of the AC motor. The control is simple and precise. High degree.

3 Quick commissioning Quick commissioning is required before using the inverter to drive the motor. Parameter p0010 is set to 1, p3900 is set to 1, the inverter performs quick commissioning. After the quick commissioning is completed, the necessary motor data is calculated and all other parameters are restored to their default settings. In the vector or torque control mode, in order to achieve the correct control, it is very important that the motor data must be correctly input to the inverter, and the automatic detection parameter p1910 of the motor data must be performed when the motor is at room temperature. When this function is enabled (p1910 =1), an alarm signal a0541 is generated, giving a warning, and the automatic detection of the motor parameters is started immediately after the on command is issued.

4 Acceleration/deceleration time adjustment The acceleration time is the time required for the output frequency to rise from 0 to the maximum frequency. The deceleration time is the time required to fall from the maximum frequency to 0. The reasonable selection of acceleration time and deceleration time has a significant impact on the starting and stopping of the motor and the response speed of the speed control system. The constraint of the acceleration time setting is to limit the current to the overcurrent range and should not cause the overcurrent protection device to operate. During the deceleration operation of the motor, the inverter will be in the regenerative braking state. The mechanical energy stored in the drive train is converted to electrical energy and the electrical energy is fed back to the DC side via the inverter. The feedback of the electrical energy will cause the voltage across the storage capacitor of the intermediate circuit to rise. Therefore, the constraint of the deceleration time setting is to prevent the DC link voltage from being too high. The formula for calculating the acceleration and deceleration time is:
Acceleration time: ta=(jm+jl)n/9.56(tma-tl)
Deceleration time: tb=(jm+jl)n/9.56(tmb-tl)
Where: jm is the inertia of a motor
Jl — load inertia
n — rated speed
Tma—motor drive torque
Tmb — motor braking torque
Tl — The load torque acceleration/deceleration time can be calculated according to the formula, or it can be set by simple test method. First, let the drag system run at the rated speed (power frequency operation), then cut off the power supply, so that the drag system is in the free braking state, and use the stopwatch to calculate the time required for the speed to drop from the rated speed to the stop. The acceleration/deceleration time can be preset by 1/2~1/3 of the free braking time. By starting and stopping the motor to observe whether there is overcurrent or overvoltage alarm, adjust the acceleration/deceleration time setting value, and repeat the operation several times to determine the optimal acceleration/deceleration time.

5 Moment of inertia setting The setting of motor and load moment of inertia is often neglected. It is considered that the correct setting of acceleration/deceleration time can ensure the normal operation of the system. In fact, improper setting of the moment of inertia will cause the system to oscillate, and the speed regulation accuracy will also be affected. Moment of inertia formula:
j=t/dω/dt
The motor and the load moment of inertia are obtained in the same way, so that the operating frequency of the inverter is at an appropriate value, 5 to 10 hz. Let the motor run at no load and load, read the rated torque of parameter r0333 and the starting time of r0345 motor, then convert the working frequency of the inverter into the corresponding angular velocity and substitute the formula to calculate the moment of inertia of the motor and load. Set parameter p0341 (motor inertia) to parameter p0342 (driver total inertia / motor inertia ratio) so that the frequency converter can be better regulated.

6 Conclusion There are more and more brands of inverters, and the functions are constantly improved and strengthened. How to set the parameters correctly is very important for the correct use and best performance of the inverter.