Classification of frequency converters
There are many ways to classify frequency converters, which can be distinguished according to different attributes, characteristics, functions, principles of operation, and appropriate use. In this article, JACT classifies inverters from different angles and briefly analyzes these classifications.
It is divided into voltage type inverter and current type inverter according to the classification of the operation mode of the main circuit.
By classification of switching mode, it can be classified into PAM control inverter, PWM control inverter, and high carrier frequency PWM control inverter.
Depending on the operating principle, it can be divided into V / f control inverters, slip frequency control inverters, vector control inverters, etc.
It can be classified into general-purpose inverters, high-performance dedicated inverters, high-frequency inverters, single-phase inverters, and three-phase inverters according to the classification of applications.
Depending on the nature of the DC power supply, it can be divided into voltage type inverters and current type inverters. (1) The voltage type is equivalent to providing a voltage source because the energy storage element is a capacitor and the control amount is voltage. Dynamic response is slow. When applying the brakes, it is necessary to install an anti-parallel inverter on the power supply side. Achieve energy feedback. , Can be adapted to multi-motor drag.
The AC voltage output from the inverter is a square wave or a step wave, and the current waveform becomes close to a sine wave after filtering with a motor load, but the harmonic component becomes large. Since it is used as a voltage source to supply AC power to an AC motor, its main advantage is that it is largely unaffected by power factor and load commutation. The disadvantage is that if the load is short-circuited during inverter operation or the load is overcurrent on the load, protective measures must be taken in a very short time.
(2) Current type means that the energy storage element is a reactor. A large DC internal resistance corresponds to a current source. The dynamic response is fast and the feedback brake can be realized directly. Induction motor current type variable frequency speed control systems are frequently used and are suitable for stand-alone operation modes in which one inverter powers one motor for high speed four quadrant operation.
Its advantage is that it has a four-quadrant operating capability and can easily realize the braking function of the motor. The disadvantage is that the inverter bridge needs to be forced to commutate, which complicates the device structure and makes it more difficult to adjust. In addition, since the power grid side uses an SCR phase shift commutator, the harmonics of the input current are relatively large, and the large capacity has a certain effect on the power grid.
Classification according to the direction of use: mini type, general type, vector type, special type.
1.Mini Inverter: Ideal for customers with small equipment. The mini inverter is beautiful in appearance, convenient to operate, and lightweight. It features a compact design and excellent performance. Obviously, it is suitable for some customers who do small equipment.
2.General purpose inverter: Fully functional, powerful and stable, suitable for driving conventional loads: Roche fans, such as mechanical processing equipment, also need a general purpose inverter.
3.Vector inverter: It has better performance than general purpose inverters, has a large load inertia, and is suitable for load situations with low frequency and high torque starting (that is, allowing the load to operate at low frequencies).
4. Dedicated inverter: The dedicated inverter is for designated industries.
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