Brief description of the main circuit and control circuit structure of the inverter

The frequency converter is an electrical device that controls the speed and performance of the motor and is widely used in the field of industrial automation control. It can control the output frequency and voltage of the AC motor, and then control the speed and torque of the motor, thereby realizing intelligent, efficient and energy-saving control of the equipment.

The inverter is mainly composed of the transmission part, the rectifier part, the inverter part, the control circuit, etc. The transmission part reduces the voltage of the input grid (usually 380V/220V) to the required input voltage through the transformer, the rectifier part converts the input AC into DC, the inverter part converts DC into high-frequency AC, and the control circuit realizes the routing and processing of the control signal, thereby controlling the output of the inverter.

The main functions of the inverter are to realize the motor's speed control, power regulation and mains overvoltage, overload and other protection functions. By adjusting the inverter output frequency and voltage, the motor can be reliably and accurately controlled under different loads, and a variety of motor control strategies can be implemented, such as range control, vector control, open-loop control, etc.

由于变频器具有运行稳定、效果显著、节能降耗等优势，广泛应用于各种生产工艺和领域，如水泵控制、通风系统、冷却系统、工厂生产以及机器人等领域。

Working principle of frequency converter

The frequency converter is an electrical device used to adjust the running speed of an AC motor. Its basic working principle is as follows:

The inverter converts DC power into AC power and adjusts the motor's operating speed and torque by controlling parameters such as voltage, frequency and phase. Its specific working process can be roughly divided into the following steps:

1. Rectification: The inverter converts the AC power of the power supply into DC power through a rectification circuit.

2. Filtering: Through the filtering circuit, the DC power is smoothly transmitted to the inverter circuit to prevent the high-frequency pulse noise of the current from polluting the power supply.

3. Inversion: Convert direct current into the required alternating current through an inverter circuit.

4. Output control: The frequency converter adjusts the working state of the motor by controlling the voltage, frequency and phase output by the inverter circuit to achieve stepless speed control of the motor.

5. Protection function: The inverter also has a variety of protection functions, such as overcurrent, overload, overvoltage, undervoltage and other protections to ensure the safe and stable operation of the motor and inverter.

In general, the frequency converter adjusts the working state of the motor by controlling parameters such as the frequency and voltage of the alternating current, enabling it to achieve stepless speed control, thereby meeting the control requirements of the motor in different occasions.

Main circuit structure of the inverter

The main circuit structure of the inverter mainly includes: rectifier circuit, intermediate capacitor, inverter circuit and output filter circuit. Specifically, it mainly consists of the following parts:

1. Rectifier circuit: The rectifier circuit of the inverter is mainly composed of a rectifier bridge and a DC capacitor. A rectifier bridge and a DC filter are added to the original AC input end to convert the AC voltage into a DC voltage.

2. Intermediate capacitor: The intermediate capacitor is mainly used to ensure the smoothness and stability of the DC voltage of the inverter, and can also act as an output filter.

3. Inverter circuit: The inverter circuit mainly includes various topologies such as half-bridge and full-bridge, which realize the conversion from DC voltage to AC voltage, and output AC voltage with a sinusoidal waveform through PWM control to achieve speed control.

4. Output filter circuit: The output filter circuit mainly includes two types: L-type filter and LC-type filter, which are used to filter out the high-frequency noise generated by the inverter circuit and form a smooth sinusoidal DC voltage at the output port.

In general, the main circuit structure of the inverter should select different components according to the actual usage requirements, including active devices (such as IGBT, MOSFET, etc.) and passive devices (capacitors, inductors, etc.), etc., to achieve stepless speed control of the motor.

Control circuit structure of frequency converter

The control circuit structure of the inverter is mainly divided into peripheral interface, input signal processing unit, central processing unit, output signal control unit and power supply unit.

1. Peripheral interface: includes the connection interface of input and output signals, used for communication and interaction with external devices.

2. Input signal processing unit: used to process and convert various input signals. It can accept multiple input signals, such as analog or digital quantities, and convert them into standard control signals and output them to the central processing unit to realize the recognition and processing of control signals.

3. Central Processing Unit: It is the core part of the inverter, responsible for calculating and controlling the output frequency and voltage of the motor, and controlling the operation of the output components, such as IGBT inverters, etc. The central processing unit usually contains one or more CPUs and internal memory for storing setting parameters and control programs.

4. Output signal control unit: used to control the operation of the output components. By controlling the output components such as IGBT, the output frequency and voltage of the motor can be adjusted, and the speed and torque of the motor can be controlled.

5. Power supply unit: provides stable power supply, and filters and smoothes the high-frequency pulsation output by the motor through components such as filters to ensure the stability and reliability of the system.

In summary, the control circuit structure of the inverter is composed of multiple modules, each of which plays a specific role and works together to realize the control function of the inverter.