With the continuous development of industrial automation, the inverter has also been more user approval. At the same time, users have more questions. The following briefly describes the inverter circuit.
The main circuit of the inverter mainly consists of three parts of the rectifier circuit, the inverter circuit and the DC intermediate circuit, and the related auxiliary circuits.
1, rectifier circuit
Rectifier circuit's main role is to rectify the AC power grid to the inverter circuit and control circuit to provide the required DC power. In current mode inverters, the rectification circuit acts as a DC current source, whereas in voltage mode inverters the rectification circuit acts as a DC voltage source. Rectifier circuit also has many forms according to the rectifier components used.
2, inverter circuit
Inverter circuit is the most important part of the inverter. Its main function is to convert the DC voltage (current) output by the DC intermediate circuit into an AC voltage (current) with the required frequency under the control of the control circuit. Inverter output is the inverter output, it is used to achieve speed control of induction motors.
3, DC intermediate circuit
Although DC voltage or DC current can be obtained from the mains AC supply using rectification circuits, this voltage or current contains voltage or current ripple at six times the frequency of the power supply. In addition, inverter inverter circuit will also produce ripple voltage and current due to output and carrier frequency, which in turn will affect the quality of DC voltage or current. Therefore, in order to ensure that the inverter circuit and the control power supply can obtain a higher quality DC current or voltage, the output of the rectification circuit must be smoothed to reduce voltage or current fluctuations. This is the role of DC intermediate circuit. Because of this, the DC intermediate circuit is also called a smoothing circuit.
For voltage type inverter, the output of the rectifier circuit is DC voltage, and the DC intermediate circuit smoothes the output voltage through the capacitor of large capacity. For current mode inverters, the output of the rectification circuit is a direct current, while the direct current inquiring circuit smoothes the output current through a large-capacity inductor.
The DC capacitor used in the DC intermediate circuit of the voltage type inverter is a large-capacity aluminum electrolytic capacitor. In order to get the required voltage value and capacity, often according to the voltage and frequency converter capacity requirements of the capacitor in series and parallel use.
When the rectification circuit is a diode rectification circuit, since a large charging current (inrush current) will flow in the capacitor during power-on, there is a possibility of burning diodes and affecting the normal operation of other devices in the same power system, it is necessary Take corresponding measures.
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