How does the inverter work? Look at this professional explanation.

Inverter is to convert direct current energy (battery, storage battery) into alternating current (generally 220V, 50Hz sine wave). It consists of inverter bridge, control logic and filter circuit. Let's have a deep understanding of the working principle of frequency converter.

First, the working principle of frequency converter

Working principle of 1. Fully-controlled inverter: It is a common main circuit of single-phase output full-bridge inverter, and its AC components are IGBT tubes Q 1 1, Q 12, Q 13 and Q 14. The turn-on or turn-off of IGBT tube is controlled by PWM pulse width modulation.

When the inverter circuit is connected to the DC power supply, it is first turned on by Q 1 1 and Q 14, and then turned off by Q 1 and Q 13, and then the current is output by the positive pole of the DC power supply, passing through Q 1 1, L. When Q 1 1 and Q 14 are turned off, Q 12 and Q 13 are turned on, and the current returns from the positive pole of the power supply to the negative pole of the power supply through Q 13 and the transformer primary coil 2- 1. At this point, the alternating square wave has been formed on the primary winding of the transformer. By using high-frequency PWM control, two pairs of IGBT tubes are alternately repeated, generating AC voltage on the transformer. Due to the function of LC AC filter, sine wave AC voltage is formed at the output end.

When Q 1 1 and Q 14 are turned off, in order to release the stored energy, diodes D 1 1 and D 12 are connected in parallel to the IGBT to return the energy to the DC power supply.

2. Working principle of semi-controlled inverter: The semi-controlled inverter adopts thyristor elements. The main circuit of the improved parallel inverter is shown in Figure 4. In the figure, Th 1 and Th2 are thyristors working alternately. If Th 1 is turned on first, the current will flow through Th 1 through the transformer, and at the same time, the commutation capacitor C will be charged to twice the power supply voltage due to the induction of the transformer. According to Th2, conduction is triggered, and Th 1 is turned off and returns to the off state due to reverse bias applied by the anode of Th2. In this way, Th 1 commutates with Th2, and then the capacitor C is charged in reverse polarity. In this way, the thyristor is triggered alternately, and the current flows to the primary of the transformer alternately, and the alternating current is obtained at the secondary of the transformer.

The inductance L in the circuit can limit the discharge current of the commutation capacitor C, prolong the discharge time, and ensure that the turn-off time of the circuit is longer than that of the thyristor, without the need of a large-capacity capacitor. D 1 and D2 are two feedback diodes, which can release the energy in the inductor L and send the remaining energy back to the power supply to complete the energy feedback.

Second, the inverter classification detailed explanation

1, which is divided into power frequency inverter, intermediate frequency inverter and high frequency inverter according to the frequency of alternating current output by the inverter. Frequency converter with frequency of 50 ~ 60 Hz; The frequency of intermediate frequency inverter is generally 400Hz to more than ten kHz, and the frequency of high frequency inverter is generally more than ten kHz to MHz.

2. According to the number of phases output by the inverter, it can be divided into single-phase inverter, three-phase inverter and multi-phase inverter.

3. According to the direction of inverter output power, it can be divided into active inverter and passive inverter. An inverter that transmits the electric energy output by the inverter to the industrial power grid is called an active inverter. An inverter that transmits the electric energy output by the inverter to an electric load is called a passive inverter.

4. According to the main circuit of inverter, it can be divided into single-ended inverter, push-pull inverter, half-bridge inverter and full-bridge inverter.

5. According to the types of main switching devices, the inverter can be divided into thyristor inverter, transistor inverter, field effect inverter and insulated gate bipolar transistor (IGBT) inverter. It can also be divided into "semi-controlled" inverter and "fully controlled" inverter. The former does not have the ability of self-turn-off, and the element loses its control function after being turned on, so the ordinary thyristor called "semi-controlled" belongs to this category; The latter has the ability of self-turn-off, that is, the turn-on and turn-off of any device can not be controlled by the control electrode, so it is called "full control type". Power field effect transistors and insulated gate bipolar transistors (IGBT) all belong to this category.

6. According to the DC power supply mode, it can be divided into voltage source inverter (VSI) and current source inverter (CSI). The DC voltage of the former is almost constant and the output voltage is AC square wave; In the latter, the DC current is almost constant and the transmission current is an alternating square wave.

7. According to the waveform of inverter output voltage or current, it can be divided into sine wave output inverter and non-sine wave output inverter.

8. According to the control mode of inverter, it can be divided into frequency modulation (PFM) inverter and pulse width modulation (PWM) inverter.

9. According to the working mode of inverter switching circuit, it can be divided into resonant inverter, fixed frequency hard switching inverter and fixed frequency soft switching inverter.

10, according to inverter commutation mode, it can be divided into load commutation inverter and self-commutation inverter.

The above explains the working principle and classification of frequency converter in detail, hoping to help you understand. For more, please continue to pay attention to Tuba Rabbit Decoration Network.

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