1. Sinusoidal pulse width modulation
Sinusoidal Pulse Width Modulation (SPWM) is characterized by simple structure of control circuit, low cost, good hardness of mechanical characteristics, and can meet the smooth speed regulation requirements of general transmission, and has been widely used in various fields of the industry.
However, in this control mode, at low frequency, due to the low output voltage, the torque is significantly affected by the voltage drop of the stator resistance, so that the maximum output torque is reduced. In addition, its mechanical characteristics are not as hard as DC motors, dynamic torque ability and static speed regulation performance are not satisfactory, and the system performance is not high, the control curve will change with the change of load, the torque response is slow, the motor torque utilization rate is not high, and the performance decreases due to the existence of stator resistance and inverter dead zone effect at low speed, and the stability deteriorates.
2. Voltage Space Vector (SVPWM)
Voltage Space Vector (SVPWM) It is based on the premise of the overall generation effect of the three-phase waveform, and the purpose is to approximate the ideal circular rotating magnetic field trajectory of the motor air gap, and the three-phase modulation waveform is generated at one time, and the inscribed polygon is controlled by approximating the circle.
After practical use, it has been improved, that is, the introduction of frequency compensation, which can eliminate the error of speed control; The flux amplitude is estimated through feedback, and the influence of stator resistance at low speed is eliminated. The output voltage and current are closed to improve the accuracy and stability of the dynamics.
3. Direct torque control (DTC) mode
Direct Torque Control (DTC) This technology solves the shortcomings of the above-mentioned vector control to a large extent, and has been rapidly developed with novel control ideas, concise and clear system structure, and excellent dynamic and static performance. At present, this technology has been successfully applied to the high-power AC transmission of electric locomotive traction.
Direct torque control directly analyzes the mathematical model of the AC motor in the stator coordinate system, and controls the flux and torque of the motor. It does not need to equate an AC motor to a DC motor, thus eliminating many complex calculations in vector rotation transformations; It does not need to mimic the control of a DC motor, nor does it need to simplify the mathematical model of an AC motor for decoupling.
4. Matrix communication-traffic control mode
Matrix AC-AC control mode VVVF frequency conversion, vector control frequency conversion, and direct torque control frequency conversion are all one of the AC-DC-AC frequency conversion. Its common disadvantages are that the input power factor is low, the harmonic current is large, the DC circuit requires a large energy storage capacitor, and the regenerative energy cannot be fed back to the power grid, that is, it cannot carry out four-quadrant operation. For this reason, matrix alternating frequency-alternating frequency came into being. Because the matrix AC-AC frequency conversion eliminates the intermediate DC link, the large and expensive electrolytic capacitor is eliminated.
Because the matrix AC-AC frequency conversion eliminates the intermediate DC link, the large and expensive electrolytic capacitor is eliminated. It can achieve a power factor of L, an input current of sinusoidal and four-quadrant operation, and a high power density of the system. This technology is not mature at present, and its essence is not to indirectly control the amount of current, flux, etc., but to realize the torque directly as the controlled quantity.
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More on that
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Megmeet PLC – Analysis of common failures of PLC
1. The CPU is abnormal
When the CPU is abnormally alarmed, check all the devices connected to the internal bus of the CPU unit. The specific method is to replace the potentially problematic units sequentially, find out the problematic units, and deal with them accordingly.
Second, the memory is abnormal
Memory anomaly alarm ...
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Megmeet inverter - what are the main aspects of the development of inverter in the future?
1. Intelligent network
The intelligent inverter does not need to set a lot of parameters when it is used, and it has the function of fault self-diagnosis, which has high stability, high reliability and practicability. The Internet can be used to realize the linkage of multiple inverters, and even the inverter complex in the factory.
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Megmeet inverter - the role and application of the inverter control cabinet introduction
Inverter control cabinet (inverter electrical control cabinet / electric control cabinet / electric control box) is an electrical control cabinet developed by using inverters from Siemens, ABB, Schneider, Fujifilm, Mitsubishi, Panasonic, Delta, Shilin, Inovance and other manufacturers.
According to the needs of working conditions, AC transmission can be installed in the frequency conversion cabinet.
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Common faults and solutions of Megmeet inverter
Fault one
Fault phenomenon: the leakage protection switch trips, the inverter is energized or the equipment leakage protection switch is operated during operation
Solution: 1. When the inverter drives the motor, the leakage value is larger than that of the non-inverter system, and the leakage protection value of the leakage protection switch is required to be more than 150mA, ...
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Megmeet drive common fault repair methods
When the oscilloscope looks at the current monitoring output of the driver, it is all noisy and cannot be read
Cause: The current monitoring output is not blocked from the AC power supply (transformer).
Solution: You can use a DC voltmeter to detect and investigate.
Servo motor high-speed rotation ...
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Megmeet servo drive - common faults and treatment methods of servo drives
1. The motor runs differently in both directions
Cause of failure: The phase of the brushless motor is wrong; The deviation potentiometer is in the wrong position.
Solution: Detect or detect the correct phase; Reposition the potentiometer.
2. The motor speed is abnormal
Cause of failure ...
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Megmeet inverter - the daily maintenance and overhaul of the inverter
1. Regularly dust the inverter, focusing on the rectifier cabinet, inverter cabinet and control cabinet, if necessary, the rectifier module, inverter module and the circuit board in the control cabinet can be removed for dust removal. Whether the lower air inlet and upper air outlet of the inverter are dusty or blocked due to excessive dust. The inverter is due to the ...
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Megmeet inverter - heat dissipation design considerations for high-power high-voltage inverters
(1) Select components and materials with good heat resistance and thermal stability to increase their allowable working temperature;
(2) Reduce the heat generated inside the equipment (device). To this end, micropower devices, such as low-loss IGBTs, should be used more often, and the number of heat-generating components should be minimized in the circuit design.
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Megmeet PLC - the installation method and functional requirements of the PLC
Installation:
The installation mode of PLC system is divided into centralized, remote I/O and distributed with multiple PLC networking.
Centralized does not need to set up the drive remote I/O hardware, the system response is fast, and the cost is low; Remote I/O is suitable for large systems with a range of ...
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Megmeet drives – how should high-voltage drives be maintained after they are shut down?
1. Check the surrounding situation - carefully check the ventilation and lighting of the inverter and the surrounding environment. It is necessary to ensure that the ventilation equipment is functioning properly and that the lighting equipment is in working order.
2. Check the internal cable - open the inverter cabinet door and check whether the internal cable is damaged, the cable ...
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Megmeet inverter - inverter braking mode and advantages and disadvantages introduction
What are the braking methods of the inverter? Generally speaking, braking refers to the technical measures taken during the operation of the motor due to fault protection or man-made active shutdown, and the commonly used inverter braking methods include energy consumption braking, feedback braking, DC braking and DC feedback braking. ...
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Analysis of the fault code of Megmeet welder
1. E1: indicates sensor failure. In this case, it is necessary to check whether the sensors of Megmeet are damaged or whether the wiring is loose.
2. E2: Indicates overweight load. At this point, it is necessary to check whether the load of Megmeet exceeds the set maximum load.
3. E3: Indicates battery ...
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Megmeet Inverter - Precautions for the Use of Inverter (11-21)
11. For the occasion when the inverter drives the ordinary motor for constant torque operation, long-term low-speed operation should be avoided as much as possible, otherwise the heat dissipation effect of the motor will become worse and the heating will be serious. If long-term operation at low speed constant torque is required, a variable frequency motor must be selected.
12. For the promotion of negative ...
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Megmeet PLC – How does PLC communicate with computers?
1. In this computer, right-click, manage, check to find the device manager, plug in the USB-PPI cable (one end is connected to the computer, the other end is connected to the PLC), the computer device manager will pop up the port USB-SERLAL CH304 (com3), the number in parentheses may change, indicating that you have found the cable. This...
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The causes of the failure of the Megmeet welding machine and how to deal with it
1. The welding machine has no welding current output
1. Cause of failure: the internal wiring of the non-voltage input at the input end of the welding machine falls off or the internal coil of the broken circuit is burned out.
2. Treatment method: check whether the switch, wire, fuse and connection parts from the distribution box to the input end of the welding machine are in good condition.
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Megmeet drives – the replacement steps for high-voltage drive power units
1) Shut down, so that the inverter out of the operating state;
2) Cut off the high-voltage power supply and push out the high-voltage cabinet trolley (when there is a bypass cabinet. The inverter can be isolated by the disconnecting switch of the bypass cabinet), the local or remote high-voltage disconnect switch can be locked, and the high-voltage cabinet grounding switch can be grounded;
3) Hit ...
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Megmeet welding machine - the application and precautions for the use of butt welding machine
The butt welding machine should be settled indoors, and should have a reliable grounding or zero connection, when a plurality of butt welding machines are connected to each other, the distance from each other shall not be less than 3m, and they should be connected to different corresponding power grids, and should have their own knife switches.
Before welding, the pressure of the butt welder should be checked and determined.
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Megmeet inverter - maintenance precautions and items for high-voltage inverters
Precautions for maintenance of high-voltage inverters
1. Carefully monitor and record the display parameters on the man-machine interface of the inverter, and reflect the abnormality immediately
2. Carefully monitor and record the ambient temperature of the inverter room, and the ambient temperature should be between -5 °C and 40 °C. Phase-shifting transformers ...
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Common faults and solutions of Megmeet inverter
Fault one
Fault phenomenon: the leakage protection switch trips, the inverter is energized or the equipment leakage protection switch is operated during operation
Solution: 1. When the inverter drives the motor, the leakage value is larger than that of the non-inverter system, and the leakage protection value of the leakage protection switch is required to be more than 150mA, ...
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Megmeet drives – the design essentials of the drive control cabinet
The inverter should be installed inside the control cabinet, and the design of the control cabinet should pay attention to the following issues:
1. Wiring specification of inverter
The signal line and the power line must be separated: When using an analog signal to remotely control the inverter, in order to reduce the interference of the analog signal to equipment such as the inverter, ...
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