According to the nature of DC power supply, the types of frequency converters can be divided into \x0d\A, voltage type-the energy storage element is a capacitor, and the control quantity is voltage, which is equivalent to providing a voltage source. Its dynamic response is slow, so it is necessary to set an anti-parallel inverter on the power supply side to realize energy feedback during braking, which can adapt to multi-motor drag. \x0d\ The AC voltage output by its inverter is a rectangular wave or a stepped wave, while the current waveform is close to a sine wave after being filtered by the motor load, but it has a large harmonic component. Because it is used as a voltage source to provide AC electric power to AC motor, its main advantage is that its operation is almost unaffected by load or commutation power factor; The disadvantage is that when the load is short-circuited or put into operation under the condition of frequency converter, it is easy to have overcurrent, so protective measures must be applied in a very short time. \x0d\B, current type —— The energy storage element is a reactor, which is equivalent to providing a current source with large DC internal resistance, with fast dynamic response and direct feedback braking. The current-mode variable frequency speed regulation system of induction motor can realize four-quadrant operation frequently and quickly, which is more suitable for single-machine operation mode in which inverter supplies power to the motor. \x0d\ has the advantage of four-quadrant operation ability, and can conveniently realize the braking function of the motor. The disadvantage is that the inverter bridge needs forced commutation, and the device structure is complex and difficult to adjust. In addition, because the power grid side adopts SCR phase-shifting rectification, the input current harmonic is large, which will have a certain impact on the power grid when the capacity is large. \x0d\(2) Classification according to working principle \x0d\A, V/f control -V/F control inverter is a control to ensure that the output voltage is proportional to the frequency, so as to keep the motor flux constant and avoid the phenomena of weak magnetism and magnetic saturation. It is mostly used for energy saving of fans and pumps, which is realized by voltage-controlled oscillators. \x0d\ The torque of asynchronous motor is produced by the interaction between the flux of motor and the current flowing in the rotor. At the rated frequency, the voltage will definitely reduce the frequency, the magnetic flux will increase, the magnetic circuit will be saturated, and the motor will be burned out in severe cases. When the frequency and voltage change in proportion, the magnetic flux of the motor remains unchanged to avoid weak magnetism and magnetic saturation. \x0d\B, slip frequency control-slip speed regulation is to change the slip of asynchronous motor into speed regulation. The greater the slip, the slower the speed. Knee winding is the series resistance of motor rotor. The adoption of slip frequency control technology makes the variable frequency speed regulation system improve the static and dynamic performance of the system to some extent. At the same time, compared with vector control method, it has the characteristics of simple structure, easy realization and high control accuracy, and is widely used in vector control speed regulation of asynchronous motors. \x0d\ does not need complicated flux detection and complicated coordinate transformation. As long as the magnitude of rotor flux linkage is constant, indirect field-oriented control can be realized by detecting stator current and rotor angular velocity and calculating mathematical model. To improve the dynamic performance of speed regulation system, we mainly rely on controlling the rate of change of speed. Obviously, the purpose of control can be achieved by controlling the sideslip angle frequency. \x0d\C, vector control-According to the characteristics of DC motor speed control, the stator winding current of asynchronous motor is decomposed into magnetic field current component and torque current component similar to DC motor by vector transformation method. As long as the magnitude and phase of the stator winding current of asynchronous motor are controlled, the excitation current and torque current can be controlled, so that the speed control of AC asynchronous motor can be as good as that of DC motor. \x0d\ is characterized by large low-frequency torque, fast dynamic response and flexible control, and is generally used in harsh working environment and systems requiring high-speed response and high-precision electric drive. \x0d\ This article comes from: Sai Microelectronics Network-Electronic Engineer Community Original address: Please explain that the information comes from extraordinary confidential information when contacting me. The content of this information does not represent the opinion of confidential information. Please check the authenticity and legality of the content yourself. 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