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Home » News » industry information » Performance comparison between voltage and current type inverters (II)

Performance comparison between voltage and current type inverters (II)

Views: 0     Author: Site Editor     Publish Time: 2018-12-15      Origin: Site

There are many types of high-voltage inverters, and their classification methods are also diverse. According to the intermediate part, there is no DC part, which can be divided into AC frequency converter and AC line frequency converter; according to the nature of DC part, it can be divided into current type and voltage type frequency converter.

 

Current type inverter:

Because it is named after the DC component of the inverter, it has the advantage of four-quadrant operation capability, which can easily realize the braking function of the motor. The disadvantage is that the inverter bridge needs to be forced to commutate, the device structure is complicated, and the adjustment is difficult. In addition, since the grid side adopts thyristor phase shift rectification, the input current harmonics are large, and the capacity will have a certain impact on the grid.

 

Voltage type inverter:

Because it is named after the capacitor component in the DC link of the inverter, it is characterized by the inability to perform four-quadrant operation. When the load motor needs braking, an additional brake circuit is required. When the power is large, the output also needs to add a sine wave filter.

 

What is the difference between voltage type and current type?

The main circuit of the inverter can be roughly divided into two types: the voltage type is a frequency converter that converts the direct current of the voltage source into an alternating current, the filtering of the direct current circuit is a capacitor, and the current type is a frequency converter that converts the direct current of the current source into an alternating current. Its DC loop filtering is an inductor.

 

Why is the voltage and current of the inverter changed in proportion?

The torque of the asynchronous motor is generated by the interaction between the magnetic flux of the motor and the current flowing through the rotor. At the rated frequency, if the voltage is constant and only the frequency is reduced, the magnetic flux is too large, and the magnetic circuit is saturated. The motor will be burned. Therefore, the frequency and voltage should be changed in proportion, that is, the frequency of the inverter is controlled while changing the frequency, so that the magnetic flux of the motor is kept constant to avoid the occurrence of weak magnetic and magnetic saturation. This type of control is mostly used for energy-saving inverters such as fans and pumps.


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