1. U/f stable control
U/f control is to change the voltage of the motor power supply together with changing the frequency of the motor power supply, so that the magnetic flux of the motor is kept constant, and the efficiency and power factor of the motor do not decrease within a wide range of speed regulation. Because it is the ratio of voltage to frequency, it is called U/f manipulation. The primary problem of safe U/f control is that the low-speed function is poor, and when the speed is extremely low, the electromagnetic torque cannot overcome the large static friction force, and the torque compensation of the motor and the change of the habitual load torque cannot be properly adjusted; The second is that it is not possible to accurately control the practical speed of the motor. Since the constant U/f inverter is open-loop control of the speed, it can be seen from the mechanical characteristics of the asynchronous motor that the setting value is the stator frequency, which is the ideal no-load speed, and the practical speed of the motor is determined by the slip rate, so the stability error in the U/f stable control mode cannot be controlled, so the practical speed of the motor cannot be accurately controlled.
2. Slip frequency control
The slip frequency is the difference between the frequency of the communication power supply applied to the motor and the speed of the motor. According to the stable mathematical model of the asynchronous motor, when the frequency is constant, the electromagnetic torque of the asynchronous motor is proportional to the slip rate, and the mechanical characteristics are linear.
Slip frequency control is to manipulate torque and current by manipulating the slip frequency. The output of the speed regulator is the slip frequency, and then the sum of the motor speed and the slip frequency is the given frequency of the inverter. Compared with U/f operation, its acceleration and deceleration characteristics and ability to constrain overcurrent are improved. In addition, it has a speed regulator, which uses speed feedback to form a closed-loop control, and the static error of the speed is small. However, in order to achieve steady-state control of an automatic control system, outstanding dynamic functions cannot be achieved.
3. Vector manipulation
Vector manipulation, also known as field-oriented manipulation. It was first proposed by F. Blasschke et al. in West Germany in the early 70s, and this principle was illustrated by comparing DC motors and AC motors. This was the first of its kind to communicate motors and equivalent DC motors. The method of vector control frequency conversion speed regulation is to communicate the current Ia, Ib and Ic of the stator of the asynchronous motor in the three-phase coordinate system. After the three-phase and two-phase change, it is equivalent to the communication current Ia1 and Ib1 in the two-phase stationary coordinate system, and then the DC current Im1 and It1 are equivalent to the DC current under the synchronous rotation coordinate system after the directional rotation and rotation according to the rotor magnetic field (Im1 is equivalent to the excitation current of the DC motor; IT1 is equivalent to the armature current of the DC motor), and then the control quantity of the DC motor is obtained by imitating the control method of the DC motor, and the control of the asynchronous motor is realized through the corresponding coordinate reversal. The presentation of the vector control method makes the frequency conversion speed regulation of the asynchronous motor in an all-round advantageous position in the field of motor speed regulation. However, vector control skills require the correct budget of motor parameters, and how to improve the accuracy of parameters has always been a research topic.
Fourth, direct torque control
In 1985, Professor DePenbrock of Ruhr University in Germany first proposed the theory of direct torque manipulation, which largely solved the lack of vector manipulation, which is not through the manipulation of the current, the flux and the same amount of direct control of torque, but the torque is directly manipulated as a controlled quantity. The superiority of torque control lies in the fact that torque control is to control the stator flux, which does not require speed information in essence, and has outstanding robustness to all motor parameters except stator resistance. The introduction of a stator flux observer can easily calculate the synchronous speed information, so it is easy to realize the operation without a speed sensor, and this kind of operation is called direct torque control without a speed sensor.
|
More on that
|
Hope Senlan inverter selection
Hope Sunland inverter is a high-performance inverter product, which has high operational reliability, high energy efficiency, strong control performance and long service life. Hope Sunland inverter has been widely used in industrial process production control, machinery control, water treatment, construction and transportation and other fields. This article will start with ...
|
|
The cause of the leakage problem of Sunland inverter
1. The cause of inverter leakage
According to the inverter to control the operation of the motor, the three-phase electricity is supplied to the inverter bridge (IGBT) through the filter capacitor through the rectification, and then the operation of the motor is controlled by the three-phase electricity with adjustable output frequency and voltage of the inverter.
We all know that the three-phase stator winding of the motor ...
|
|
Servo motor regular diagnosis and repair method - Senlan
1. Common faults of motor heating up too high or smoke motor
Causes: 1. Excessive load; 2. Two-phase operation; 3. Blocked air duct; 4. The working temperature is too high; 5. Interphase or inter-turn short circuit fault of motor stator winding; 6. Motor stator winding grounding device; 7. The power supply voltage is too high or too low;
Overhaul...
|
|
Sunland - inverter operation process and factory value restoration
The general operation process is as follows:
Enter the program through the operation panel and set the parameters, and set the relevant parameter groups such as the start-stop method, operation and control form according to the requirements of the industrial control. After confirming that the wiring is correct, the no-load power on test run and ...
|
|
The reason for the increase of the torque of the inverter - Senlan inverter
It is important to set the torque to improve the function. When the power frequency of the motor decreases, the speed of the motor will also decrease, and if the load torque remains unchanged, the output power will also decrease. According to the principle of conservation of energy, if the rotation of the load ...
|
|
The change of frequency conversion control mode - Senlan
In the process of practical speed regulation, a general frequency-adjustable communication power supply can not meet the requirements of speed regulation and control of asynchronous motors, and must also take into account the problems of using the magnetic field of the motor, pressing the starting current and obtaining the desired torque characteristics, such as low-frequency torque characteristics.
|
|
The overload capacity of the dry-type transformer - Sunland inverter
Dry-type transformer is a kind of power equipment, and under normal circumstances, dry-type transformer also requires a certain amount of overload, that is, the workload beyond its working ability. So what about the overload of dry-type transformers and how to influence them?
...
|
|
Inverter device inspection and maintenance work steps
1. Preparation process:
Abort the device and admit that the motor is completely aborted.
Press the stop button on the operator panel to stop the operation.
Disconnect the external mains power supply (low-voltage cabinet drawer). Adequate security treatment should be carried out to ensure that it is indeed disconnected and that it does not ...
|
|
Senlan direct torque control principle
The direct torque control (DTC) function of the inverter is another high-performance communication frequency conversion speed regulation system developed after vector control. In the mid-80s of the 20th century, the German scholar Depenbrock proposed the theory of direct torque control in 1985, and his idea was to combine the electric motor and the inverter.
|
|
Failure of robot contactor and inverter - Senland
Robot contactors are noisy?
Cause:
It is likely that the joint contact surface of the contactor is uneven, and the surface is sand or rust. The result will constitute a phase loss, which will lead to the burnout of contactors, switch frequency conversion and other components.
Solution:
will control the ...
|
|
Application of Sunland inverter on gantry milling machine
The gantry milling machine is a machining equipment for processing larger workpieces, and its electrical control system includes two parts: the main transmission of the workbench and the logical control of the feed organization. Henan Jiaozuo Maike Company has a gantry milling machine, which has been used for many years since the 70s. The main drive of the operating table of the gantry milling machine is selected ...
|
|
Sunland inverter wiring standard
It is necessary to separate the signal line from the power line: when using analog signals for long-distance control of the inverter, in order to reduce the disturbance of the analog amount from the inverter and other equipment, please separate the signal line of the control inverter from the strong current circuit (main circuit and sequential control circuit). Inverter ...
|
|
The servo motor is connected to the wrong wire and causes a problem - Senlan
If the three power cables of the servo motor (SM) are not connected correctly, there may be no alarm in the static state. But as soon as the motor is operated manually or actively, the motor jumps off or starts to flutter, such as jumping when the speed is added too high, the system will issue generalized faults, etc.
|
|
The control mode of low-voltage general-purpose inverter - Sunland inverter
Voltage Space Vector (SVPWM) Manipulation Method:
It is based on the premise of the overall generation effect of the three-phase waveform, with the intention of approximating the ideal circular rotating magnetic field trajectory of the motor air gap, generating the three-phase modulation waveform at one time, and controlling it by approaching the circle with inscribed polygons. In practice, ...
|
|
Inverter-related knowledge - Senlan inverter
1. What does open-loop mean in the use of inverters?
The speed detector (PG) is installed on the motor equipment in operation, and the speed response of the actual speed is sent to the control equipment, which is called "closed loop", and the speed detector that does not use PG is called "open loop". Most general-purpose drives are open-loop ...
|
|
The control performance standard of the inverter cabinet
The control specifications of the inverter cabinet include reliability, accuracy, safety, environmental habits and versatility, etc., which are important guarantees to ensure the normal operation and safe production of the inverter cabinet control system.
Reliability specification: The control system should have high reliability and can be used for a long time.
|
|
The reason for adding a frequency converter to the crane control system - Senland
Prior to the introduction of frequency converters, overhead crane operators operated the cranes using contactor-based controls. For low-cycle cranes, the system is equipped with a single or two-speed motor. For cranes with higher load cycles, they use so-called wound rotor motors.
...
|
|
The reason for the humming sound after the motor plus the frequency conversion governor - Senlan
The so-called "hum" sound, that is caused by the frequency of the inverter's output waveform carrier, generally if the inverter you use is a fixed carrier, at the moment the motor is screaming, the human ear is more stimulated, then you can adjust the carrier frequency (inverter skills manual function table ...
|
|
The reason for adding a frequency converter to the crane control system - Senland
Prior to the introduction of frequency converters, overhead crane operators operated the cranes using contactor-based controls. For low-cycle cranes, the system is equipped with a single or two-speed motor. For cranes with higher load cycles, they use so-called wound rotor motors.
...
|
|
Inverter overcurrent protection solution - Senlan
1. Causes of overcurrent
There are many reasons for the occurrence of overcurrent, including soft and hard problems.
1. Causes of soft failures
When the acceleration or deceleration time in the inverter parameters is set too short, and the motor power is heavy, it means that in the acceleration, the inverter's ...
|
|
Contact
working hours
