Sequential Connection of Frequency Converters for Controlling Electric Drive Units
In this article, we will discuss the sequential connection of frequency converters responsible for controlling electric drive units in individual operations into a common network. This connection allows solving the optimization tasks for the operation of all components.
Main Components of Conversion Devices
All frequency converters have several different input and output terminals, the main ones of which we will discuss below:
- AI – analog type input terminal. It is intended for receiving an analog signal within the standard industrial range of 0(4)…20 mA or 0…10 V. This terminal allows the device to change its operating mode under the influence of a control signal.
- DI – discrete type input terminal. It receives discrete signals of various levels and frequencies, responding to rapid changes in amplitude or frequency of the input. This can also lead to a change in the operating mode of the frequency converter.
- AO – analog type output terminal. This terminal produces an electrical signal within the standard range of 0(4)…20 mA or 0…10 V, which can be used for monitoring the device's operating mode.
- DO – discrete type output terminal. Outputs of this type can generate sharp amplitude fluctuations or change the output frequency according to the operating mode.
RS-485 Interface
The RS-485 interface is a full-fledged digital channel capable of interacting with frequency converters, including through a personal computer. It allows the transmission of digital signals via two-wire communication lines.
Connecting Conversion Devices in a Network
The sequential connection of converters is based on the master converter, which performs the main operations. Peripheral converters, such as “Known” or “SLAVE”, carry out secondary functions.
Configuration of Analog and Discrete Signals
- Analog Type Signal: The analog output terminals of the master converter are connected to the analog input terminals of peripheral devices. The configuration of input/output parameters is performed via a menu considering the operating modes.
- Discrete Type Signal: The discrete output of the master frequency converter is connected to the discrete inputs of the peripheral devices. The configuration of discrete input/output parameters is also done through the menu.
Configuring the RS-485 Interface
The connection of devices is performed using “twisted pair” wiring, starting from the master converter. In the settings of the master frequency converter, the device state is selected as “MASTER” and the data transmission speed is configured. Identical information transmission parameters are assigned to peripheral frequency converters, and each device is assigned a unique network number. Correction coefficients for responding to commands from the master converter are set according to the requirements of the technological process.