The working principle of the inverter and the PLC control programming

To put it simply, the principle is AC-DC-AC, input voltage to the inverter, and then input the nameplate parameters on the motor on the control panel, and the control can be realized. After communicating with the PLC, it realizes automatic control according to the instructions issued by the PLC.

There are four ways to control the speed regulation of PLC control inverter:

1. Analog control, the DA module of the PLC outputs 4-20mA or 0-10V to the analog input terminal of the inverter.

2. Switching control, most inverters have up down terminals, which can increase speed and decrease speed through switching signals and resolution. The PLC only needs to output two switching signals and increase or decrease the speed as needed.

3. Multi-stage speed control, the inverter has 7-stage speed and 16-stage speed control mode, and the control between several different speeds can be realized through the output relay of PLC.

4. Communication methods. According to the communication protocol of the inverter, the corresponding communication control mode is selected.

How the inverter works.

DC > oscillation circuits > transformers (isolation, transformer) > AC output.

The square wave signal generator makes the DC mutate at a frequency of 50Hz, and with a sine and quasi-sine oscillator, the waveform is similar to the battlement of the Great Wall, and the square wave is about 5V; Then through the signal amplifier, the mutation amount is expanded to about 12V; Step-up to 220V output by transformer.

There are three ways to convert direct current to alternating current:

1. Use DC power supply to drive DC motor --- mechanical transmission to alternator to generate alternating current; This is one of the oldest methods, but it is still in use today, and is characterized by low cost and easy maintenance. It is still used in high-power conversion.

2. Use an oscillator (that is, the inverter on the current market); This is a relatively advanced method, with high cost, and is mostly used for low-power conversion;

3. The principle of mechanical oscillator converter is to make the DC current intermittent, and after passing through the transformer, it can output alternating current in the secondary stage of the transformer, which is a relatively old methodAdditional Information:

Inverters can also be used in home appliances. Among the home appliances that use inverters, there are not only motors (such as air conditioners) but also fluorescent lamps.

Frequency converters for motor control that can change both voltage and frequency. However, frequency converters for fluorescent lamps are mainly used to regulate the frequency of the power supply.

The working principle of frequency converters is widely used in various fields. For example, in the power supply of computer power supplies, frequency converters are used to suppress reverse voltages, frequency fluctuations, and momentary power outages of the power supply.

The inverter mainly adopts AC-DC-AC mode (VVVF frequency conversion or vector control frequency conversion), which first converts the power frequency AC power supply into DC power supply through the rectifier, and then converts the DC power supply into AC power supply that can be controlled by frequency and voltage to supply the motor.

The inverter is mainly composed of rectifier (AC to DC), filtering, inverter (DC to AC), braking unit, drive unit, detection unit and microprocessor unit.

VVC control principle.

In VVC, the control circuit uses a mathematical model to calculate the optimal motor excitation when the motor load changes, and compensates for the load.

In addition, the synchronous 60°PWM method integrated into the ASIC circuit determines the optimal switching time for the inverter semiconductor device (IGBTS).

The following principles should be followed in deciding on and off time:

The numerically largest phase retains its positive or negative potential for 1 6 periods (60°).

The other two phases vary proportionally so that the output line voltage remains sinusoidal and reaches the desired amplitude.

Using a PLC (Programmable Controller) to control a frequency converter to control a motor can bring several advantages:

Flexibility: The combination of PLC and inverter can flexibly realize a variety of different control strategies, such as timing start and stop, reverse rotation, speed control and so on. At the same time, the PLC itself can also be controlled and judged by logic through Ranling programming, making the entire control system more intelligent and automated.

Reliability: PLC has high reliability and stability, which can monitor and protect the running status of the motor to avoid equipment failure and safety accidents. In addition, the PLC can also communicate and transmit data, which can easily realize remote monitoring and control, and improve the reliability and production efficiency of the equipment.

Energy-saving: The use of inverter can realize the speed control of the motor and reduce the operating power of the motor, so as to achieve the purpose of energy saving. This section can be controlled by PLC to achieve more refined control according to specific needs, minimize energy consumption, and improve the economic benefits of the equipment.

In short, the use of PLC control inverter to control the motor can improve the flexibility, reliability and energy saving of the equipment, while achieving a more intelligent and automated production process, improving production efficiency and economic benefits.

Hello, it is a pleasure to serve you, as far as I know, both PLC and inverter contain micro-controlled luggage makers inside, but their internal structure is different. Programmable logic controller) is a special numerical control system used for industrial automation control. The PLC is usually composed of a processor module, an input module, an output module, and a communication module.

The processor module is mainly composed of a microprocessor and memory, which can be used to implement program execution and data processing. The input module and output module are generally composed of digital circuits and interface circuits, which are used to receive and output control signals. The communication module is used to communicate with other devices.

2.The inverter is a kind of equipment used to control the speed of the motor, which is composed of a power module, a DC bus module, an inverter module and a control module. Among them, the control module is generally composed of a single-chip microcomputer (such as ARM, DSP, etc.) or FPGA chip, etc., which is used to realize the speed regulation, protection, diagnosis and other functions of the motor.

The inverter module is composed of power switches, drive circuits, etc., which are used to realize the conversion of power from DC to AC. 3.Therefore, although both PLCs and inverters contain microcontrollers, their internal structures and application scenarios are different.

I hope the above answers are helpful to you, and I wish you a happy life and an auspicious duck in the Year of the Rabbit!

Summary. PLCs and frequency converters are usually made up of microprocessors or microcontrollers internally. PLC (Programmable Logic Controller) is a programmable controller, usually composed of a motherboard, CPU, memory, input and output interfaces, power supply, etc.

PLCs often require real-time control and flexible programming, so high-performance microprocessors and microcontrollers are often used in-house.

PLCs and frequency converters are usually made up of microprocessors or microcontrollers internally. PLC (Cosage Programmable Logic Controller) is a kind of programmable control of the trace, usually composed of a motherboard, CPU, memory, input and output interfaces, power supplies, etc. PLCs often require real-time control and flexible programming, so high-performance microprocessors and microcontrollers are often used in-house.

Both PLCs and drives may use microprocessors or microcontrollers inside them to enable complex control and regulation functions. The inverter is also composed of a motherboard, a control circuit, a power supply, an output circuit, etc., and a microcontroller is usually required to process the control signal and control the output power of the inverter's coarse hall to achieve speed control of the motor. Both PLCs and drives may use microprocessors or microcontrollers internally to enable complex control and regulation functions.

Three methods:

The output terminal is connected to the multi-function terminal of the inverter, and the multi-function terminal is set in the inverter for the multi-channel speed function, and the corresponding frequency is set. Through the combination of closing and disconnecting the output terminals of the PLC, the inverter can operate at different speeds.

Advantages: fast response speed and strong anti-interference ability.

Disadvantages: Unable to infinitely adjust the speed.

2.Through the RS485 communication interface on the PLC and the inverter, the PLC programming communication control is adopted.

Advantages: It can be continuously changed, the speed change is smooth, the speed control is accurate, and the adaptability is good.

Disadvantages: poor anti-interference, response delay.

3.Through the PLC plus digital analog (DA) conversion module, the PLC digital signal is converted into a voltage (or current depends on the inverter setting) signal, which is input to the analog control terminal of the inverter to control the inverter to work.

Advantages: stepless speed regulation.

Disadvantages: low speed regulation accuracy and unintuitive; Digital-to-analog conversion modules are more expensive.

There are only 2 ways to make the frequency of the inverter evenly added:

1. Analog control, connect the analog output of your PLC to the analog input of the inverter, set the frequency on the side of the inverter and set the external setting, if the setting is current, your PLC must use the current output, otherwise use the voltage output. The frequency of the inverter is then increased by continuously adding value to the analog output registers through the PLC.

2. Communication control, your PLC needs to connect the communication port with the communication terminal of the inverter, and then send frequency instructions according to the communication protocol supported by the inverter. The inverter side needs to set the communication parameters, and the PLC side needs to write the communication program and set the communication parameters.

I would like to add the second point of communication control, generally domestic and Taiwanese inverters, such as Delta's inverters, and PLC connections are generally RS485, Delta's all are built-in, do not add another board, and then the PLC can strain the communication address of the inverter.

Generally, 485 communication can be used to directly control the internal parameters of the inverter.

The analog output voltage signal is input into the inverter.

There are various ways to control the inverter by PLC, starting and stopping at a simple point, and setting a given speed at a complex point.

The drive can be controlled in three ways.

1. Start the inverter through the PLC switch, and control the output frequency of the inverter through the analog signal. This method is a bit simple to program, but the disadvantage is that the hardware investment is relatively expensive.

Second, through the communication mode to control the inverter start and stop and frequency given, this method is complex programming, and the communication format of different inverters is different.

3. It can also control the start and stop through the PLC, and the given frequency can be communicated.

Terminals Analog.

Communication (MODBUS, USS, PROFIBUS-DP, canopen devicenet) is acceptable.

Hardware connections.

Programmatic control. For details, see the instruction manual.